Eight states have legalized adult (aged 21 and older) personal use of marijuana and legally regulate the production, distribution, and sale of marijuana: Alaska, California, Colorado, Maine, Massachusetts, Nevada, Oregon, and Washington state. Additionally, the state of Vermont and the District of Columbia have legalized limited personal possession and cultivation of marijuana by adults aged 21 and older.

"The gateway effect, if it exists, has at least two potential and quite different sources (MacCoun, 1998). One interpretation is that it is an effect of the drug use itself (e.g., trying marijuana increases the taste for other drugs or leads users to believe that other substances are more pleasurable or less risky than previously supposed). A second interpretation stresses peer groups and social interactions. Acquiring and using marijuana regularly may lead to differentially associating with peers who have attitudes and behaviors that are prodrug generally, not only with respect to marijuana. One version of this is the possibility that those peers will include people who sell other drugs, reducing the difficulty of locating potential supplies. If the latter is the explanation, then legalization might reduce the likelihood of moving on to harder drugs compared to the current situation."

"Tetrahydrocannabinol is a very safe drug. Laboratory animals (rats, mice, dogs, monkeys) can tolerate doses of up to 1,000 mg/kg (milligrams per kilogram). This would be equivalent to a 70 kg person swallowing 70 grams of the drug—about 5,000 times more than is required to produce a high. Despite the widespread illicit use of cannabis there are very few if any instances of people dying from an overdose. In Britain, official government statistics listed five deaths from cannabis in the period 1993-1995 but on closer examination these proved to have been deaths due to inhalation of vomit that could not be directly attributed to cannabis (House of Lords Report, 1998). By comparison with other commonly used recreational drugs these statistics are impressive."

"Marijuana essentially became illegal in 1937 pursuant to the Marijuana Tax Act.³⁹ The use of marijuana required the payment of a tax for usage; failure to pay the tax resulted in a large fine or stiff prison time for tax evasion.⁴⁰ Drug prohibition was elevated to another level by targeting 'marijuana,' a plant that had never demonstrated any harm to anyone.⁴¹
"Anslinger’s [Harry J. Anslinger, the first Commissioner of the Federal Bureau of Narcotics] efforts to eradicate marijuana continued when Anslinger sought similar anti-narcotic laws against marijuana at the state level.⁴² Guided by Anslinger’s policy direction, states began passing their own laws or adopting more strident versions of federal laws.⁴³ By 1952, nearly all states had anti-narcotic laws in place.⁴⁴"

"Several meta-analyses of multiple studies found that the risk of being involved in a crash significantly increased after marijuana use¹³ -- in a few cases, the risk doubled or more than doubled.^14-16 However, a large case-control study conducted by the National Highway Traffic Safety Administration found no significant increased crash risk attributable to cannabis after controlling for drivers’ age, gender, race, and presence of alcohol.¹⁷"

Although the intent of a 'War on Drugs' may have been to target drug smugglers and 'King Pins,' according to the FBI's annual Uniform Crime Reports, of the 1,488,707 arrests for drug law violations in 2015, 83.9% (1,249,025) were for mere possession of a controlled substance. Only 16.1% (239,682) were for the sale or manufacturing of a drug. Further, the majority (43.2%) of drug arrests in 2015 were for marijuana -- a total of 643,121. Of those, an estimated 574,641 arrests (38.6% of all drug arrests) were for marijuana possession alone. By contrast in 2000, a total of 734,497 Americans were arrested for marijuana offenses, of which 646,042 (40.9%) were for possession alone.

"The law enforcement view of marijuana was indelibly shaped by the fact that it was initially connected to brown people from Mexico and subsequently with black and poor communities in this country. Police in Texas border towns demonized the plant in racial terms as the drug of 'immoral' populations who were promptly labeled 'fiends.'

"As the legal scholars Richard Bonnie and Charles Whitebread explain in their authoritative history, 'The Marihuana Conviction,' the drug’s popularity among minorities and other groups practically ensured that it would be classified as a 'narcotic,' attributed with addictive qualities it did not have, and set alongside far more dangerous drugs like heroin and morphine.

"By the early 1930s, more than 30 states had prohibited the use of marijuana for nonmedical purposes. The federal push was yet to come.

"The stage for federal suppression of marijuana was set in New Orleans, where a prominent doctor blamed 'muggle-heads' — as pot smokers were called — for an outbreak of robberies. The city was awash in sensationalistic newspaper articles that depicted pushers hovering by the schoolhouse door turning children into 'addicts.' These stories popularized spurious notions about the drug that lingered for decades. Law enforcement officials, too, trafficked in the 'assassin' theory, under in which killers were said to have smoked cannabis to ready themselves for murder and mayhem."

The Times misses part of the story when they write:
"Nearly 70 percent of the teenagers in residential substance-abuse programs run by Phoenix House, which operates drug and alcohol treatment centers in 10 states, listed marijuana as their primary problem."
http://www.nytimes.com...

Indeed. However, the majority of treatment referrals for marijuana were directly through the criminal justice system or at least in anticipation of going through the criminal justice system. Treatment alternatives to incarceration and drug courts can be effective means of dealing with drug using offenders yet they sometimes cherry-pick people to be referred to treatment, choosing those with the greatest probability of success. People who do not use drugs problematically are the most likely to succeed in drug treatment, since they didn't have a problem in the first place:
"Additional results reveal that, in practice, large numbers of drug courts are admitting offenders who are abusing alcohol and marijuana, but may not be clinically dependent or abusing more serious drugs. Consistent with the number of courts admitting individuals with lower levels of substance use and the number admitting individuals with DWI/DUI offenses, 65.6 percent of courts reported that a participant can be admitted into drug court for alcohol abuse only. An even larger percentage of courts (87.7 percent) indicated that participants can enter drug court for marijuana abuse only. Allowing participants into drug court based on alcohol abuse only did not vary by type of geographic area; however, allowing participants into drug court based on marijuana abuse only did vary geographically (X2=10.2, p<.01). The majority of courts that do not accept participants into drug court based only on marijuana abuse are located in urban areas (62.2 percent), suggesting they may have a greater focus on more serious drug problems."
Source: Rossman, Shelli B., et al., "Final Report, Volume 2: The Multi-Site Adult Drug Court Evaluation: What's Happening with Drug Courts? A Portrait of Adult Drug Courts 2004" (Washington, DC: Urban Institute, June 2011), p. 27.

According to the federal Treatment Episode Data Set, in 2011 there were 333,578 admissions to treatment with marijuana reported as the primary substance of abuse out of the total 1,844,719 admissions for all substances that year.
According to the TEDS report:
"• Marijuana was reported as the primary substance of abuse by 18 percent of TEDS admissions aged 12 and older in 2011 [Table 1.1b].
"• The average age at admission for primary marijuana admissions was 24 years [Table 2.1a], although the peak age at admission for both genders in all race/ethnicities was 15 to 17 years [Figure 12]. Forty percent of marijuana admissions were under age 20 (vs. 11 percent of all admissions), and primary marijuana abuse accounted for 74 percent of all admissions aged 12 to 14 years and 76 percent of admissions aged 15 to 17 years [Tables 2.1a-b].
"• Non-Hispanic Whites accounted for 45 percent of primary marijuana admissions (32 percent males and 13 percent females), and non-Hispanic Black males accounted for 24 percent [Table 2.3a].
"• Twenty-five percent of primary marijuana admissions had first used marijuana by age 12 and another 32 percent by age 14 [Table 2.5].
"• Primary marijuana admissions were less likely than all admissions combined to be self- or individually referred to treatment (16 percent vs. 35 percent). Primary marijuana admissions were most likely to be referred by a criminal justice/DUI source (52 percent) [Table 2.6].
"• More than 4 in 5 marijuana admissions (85 percent) received ambulatory treatment compared with about 3 in 5 of all admissions combined (62 percent) [Table 2.7].
"• Fifty-six percent of primary marijuana admissions reported abuse of additional substances. Alcohol was reported by 41 percent [Table 3.8]."
Source: Substance Abuse and Mental Health Services Administration, Center for Behavioral Health Statistics and Quality. Treatment Episode Data Set (TEDS): 2001-2011. National Admissions to Substance Abuse Treatment Services. BHSIS Series S-65, HHS Publication No. (SMA) 13-4772. Rockville, MD: Substance Abuse and Mental Health Services Administration, 2013, p. 19; and p. 43, Table 1.1a.

"Preliminary look at racial disparities in select counties of Washington

"The Crime, Cannabis & Police Research Group at Washington State University used preliminary data from a Department of Justice funded study to compare white vs. Black arrests.11 Latinos were not included in the analysis, because of difficulties measuring ethnicity in arrest data. Their main preliminary findings are that after legalization in Washington, African Americans/Blacks continue to be disproportionally arrested for the possession and selling of marijuana when compared to whites. Though the disparity in marijuana possession between African American/Blacks and whites was reduced slightly after legalization, the disparity for selling marijuana has more than doubled since legalization.

"Local trends

"While statewide studies have the ability to control for individual law enforcement agencies or police departments, monitoring trends in marijuana-related crimes within a local police department can provide details of violations that statewide data systems do not. For example, violations for public consumption of marijuana cannot be directly queried from state-derived data; however, local law enforcement agencies and municipal courts maintain details on the nature of the crime that would indicate whether someone was ticketed for public consumption vs. possession or a different drug-related charge. One example of the potential of local data to explore issues of criminal justice can be made using data from the Seattle Police Department (SPD). A 2015 report for the Seattle Community Police Commission showed a disproportionate number of citations for marijuana public consumption issued to African Americans/Blacks in Seattle.12 Using local police department data is key to understanding differences in the implementation and enforcement of polices pertaining to the legalization of marijuana."

"In these initial investigations, we found no evidence that I-502 enactment, on the whole, affected cannabis abuse treatment admissions. Further, within Washington State, we found no evidence that the amount of legal cannabis sales affected cannabis abuse treatment admissions.

"The bulk of outcome analyses in this report used the within-state approach to focus on identifying effects of the amount of legal cannabis sales. We found no evidence that the amount of legal cannabis sales affected youth substance use or attitudes about cannabis or drug-related criminal convictions.

"We did find evidence that higher levels of retail cannabis sales affected adult cannabis use in certain subgroups of the population. BRFSS respondents 21 and older who lived in counties with higher levels of retail cannabis sales were more likely to report using cannabis in the past 30 days and heavy use of cannabis in the past 30 days.

"We also found two effects that are difficult to interpret. Among the portion of the population aged 18 to 21, BRFSS respondents living in counties with higher sales were less likely to report using cannabis in the past 30 days, in some analyses. It may be that legal cannabis sales have made cannabis more difficult to access by persons below the legal age, for instance, by reducing black market supply through competition.

"We also found that in the portion of the BRFSS sample who smoked cigarettes, respondents living in counties with higher levels of legal cannabis sales were less likely to report past-month cannabis use. It is particularly difficult to explain why increased sales would lead to lower cannabis use among cigarette smokers."

In 2019, law enforcement agencies in the US made an estimated 10,085,207 arrests for all offenses, of which 1,558,862 were drug arrests.

Although the intent of a 'War on Drugs' may have been to target drug smugglers and 'King Pins,' of the 1,558,862 arrests for drug law violations in 2019, 86.7% (1,351,533) were for mere possession of a controlled substance. Only 13.3% (207,329) were for the sale or manufacturing of a drug. Further, 35.0% of drug arrests in 2019 were for marijuana offenses -- a total of 545,602. Of those, an estimated 500,395 arrests (32.1% of all drug arrests) were for marijuana possession alone. By contrast in 2000, a total of 734,497 Americans were arrested for marijuana offenses, of which 646,042 (40.9%) were for possession alone.

Table: Total Annual Arrests in the US by Year and Type of Offense, 1996-2019

"One area representative, from New York City, reported the continuing predominance in indicators and serious consequences of marijuana (as well as heroin and cocaine) and changes in marijuana trends as a key finding in that area for this reporting period. Marijuana indicator levels continued to be reported as high relative to other drugs, however, across all CEWG areas, based on treatment admissions and reports identified as marijuana/cannabis among drug items seized and analyzed. New marijuana/cannabis laws legalizing both medical and recreational marijuana use were expected by area representatives to be influencing indicators in several areas currently and in the future. Representatives from Texas and Chicago reported a shift in trafficking and marketing away from Mexican marijuana (due to a drought and poor quality Mexican marijuana) to local markets and local 'grow' operations."

In 2015:
an estimated 117,865,000 people aged 12 or older in the US had tried marijuana at least once in their lifetimes.
an estimated 36,043,000 people aged 12 or older in the US had tried marijuana at least once in the past year.
an estimated 22,226,000 people aged 12 or older in the US had tried marijuana at least once in the past month.

Click here for the complete datatable "Marijuana Use in Lifetime, Past Year, and Past Month among Persons in the US Aged 12 or Older, by Demographic Characteristics: Number in Thousands"

"In 2009-2010, past month marijuana use was reported by 6.8 percent of the U.S. population aged 12 years or older, an increase from 6.4 percent in 2008-2009 (Table C.3). Nine States that were in the top fifth for past month illicit drug use among persons aged 12 or older also were ranked in the top fifth for past month marijuana use: Alaska, Colorado, District of Columbia, Maine, Massachusetts, New Hampshire, Oregon, Rhode Island, and Vermont (Figures 2.1 and 2.9).
"Seven States were ranked in the top fifth for past month marijuana use in age groups 12 to 17, 18 to 25, 26 or older, and 12 or older: Colorado, Maine, Massachusetts, New Hampshire, Oregon, Rhode Island, and Vermont (Figures 2.9 to 2.12). The rate of past month marijuana use in the 12 or older population ranged from 3.1 percent in Utah to 11.8 percent in Alaska (Table B.3). Utah had the lowest rate in all age groups. Between 2008-2009 and 2009-2010, past month marijuana use among persons 12 or older increased in 10 States: Colorado, District of Columbia, Idaho, Illinois, Massachusetts, Michigan, New Mexico, Oklahoma, Texas, and Washington (Table C.3). During the same time period, past month marijuana use increased in one State among 12 to 17 year olds (District of Columbia), eight States among 18 to 25 year olds (Florida, Illinois, Iowa, New Mexico, North Carolina, Oklahoma, Pennsylvania, and Washington), and four States among persons aged 26 or older (District of Columbia, Idaho, Michigan, and Texas). Decreases only occurred in two States: Tennessee, among persons aged 12 or older, and Utah, among youths aged 12 to 17. All four census regions had higher rates of past month marijuana use among persons aged 12 or older in 2009-2010 compared with 2008-2009."

“When initiation of substance use occurs in preadolescence or early in adolescence, the risk of addiction is magnified.⁸ CASA’s analysis of national data finds that individuals‡ who first used any addictive substance before age 15 are six and a half times as likely to have a substance use disorder as those who did not use any addictive substance until age 21 or older (28.1 percent vs. 4.3 percent).”

"Among 50-year-old high school graduates in 2012, we estimate that about three quarters (74%) have tried marijuana, and that about two thirds (64%) have tried an illicit drug other than marijuana. (These estimates are adjusted to correct for panel attrition, as described in chapter 4 of Volume II.)
"Their current behavior is far less extreme than those statistics might suggest, but it is not by any means negligible. One in eight (12%) indicates using marijuana in the last 12 months, and one in ten (10%) indicates using any other illicit drug in the same period. Their past-month prevalence rates are lower—7.3% and 6.2%, respectively, for marijuana and any other illicit drug. About 1 in 43 (2.3%) is a current daily marijuana user, though substantially more indicate that they have used marijuana daily at some time in the past."

"Although the mean annual opioid analgesic overdose mortality rate was lower in states with medical cannabis laws compared with states without such laws, the findings of our secondary analyses deserve further consideration. State-specific characteristics, such as trends in attitudes or health behaviors, may explain variation in medical cannabis laws and opioid analgesic overdose mortality, and we found some evidence that differences in these characteristics contributed to our findings. When including state-specific linear time trends in regression models, which are used to adjust for hard-to-measure confounders that change over time, the association between laws and opioid analgesic overdose mortality weakened. In contrast, we did not find evidence that states that passed medical cannabis laws had different overdose mortality rates in years prior to law passage, providing a temporal link between laws and changes in opioid analgesic overdose mortality. In addition, we did not find evidence that laws were associated with differences in mortality rates for unrelated conditions (heart disease and septicemia), suggesting that differences in opioid analgesic overdose mortality cannot be explained by broader changes in health. In summary, although we found a lower mean annual rate of opioid analgesic mortality in states with medical cannabis laws, a direct causal link cannot be established."

"• Marijuana was the illicit drug with the largest number of persons with past year dependence or abuse in 2013, followed by pain relievers, then by cocaine. Of the 6.9 million persons aged 12 or older who were classified with illicit drug dependence or abuse in 2013, 4.2 million persons had marijuana dependence or abuse (representing 1.6 percent of the total population aged 12 or older, and 61.4 percent of all those classified with illicit drug dependence or abuse), 1.9 million persons had pain reliever dependence or abuse, and 855,000 persons had cocaine dependence or abuse (Figure 7.2)."
"• The number of persons who had marijuana dependence or abuse in 2013 (4.2 million) was similar to the number in 2012 (4.3 million) and in each year from 2002 through 2011 (ranging from 3.9 million to 4.5 million) (Figure 7.3). The rate of marijuana dependence or abuse in 2013 (1.6 percent) was lower than the rates in 2002 (1.8 percent) and 2004 (1.9 percent). Otherwise, the rate in 2013 was similar to the rates in prior years (ranging from 1.6 to 1.8 percent).
"• The number of persons who had pain reliever dependence or abuse in 2013 (1.9 million) was similar to the number in 2012 (2.1 million) and in each year from 2006 through 2011 (ranging from 1.6 million to 1.9 million) (Figure 7.3). However, the number in 2013 was higher than the numbers in 2002 to 2005 (ranging from 1.4 million to 1.5 million)."

According to the Substance Abuse and Mental Health Service's Treatment Episode Data Set, in 2015 in the US there were 213,001 admissions to treatment with marijuana reported as the primary substance of abuse out of the total 1,537,025 admissions to treatment in the US for those aged 12 and older for all substances that year. This is the lowest number of marijuana admissions and total treatment admissions in at least a decade: marijuana admissions peaked in 2009 at 373,338, and total admissions peaked in 2008 at 2,074,974.

"The issues of measurement and conceptualization described above in relation to efforts to screen for problematic or harmful cannabis use highlight the shortcomings of ‘one-size-fits-all’ approaches to screening. Our examination of the existing literature and of cannabis users from a general population study and from a mixed-methods study of adult, stable, socially integrated users suggests that many cannabis users who may otherwise meet the criteria for being at moderate risk for problematic use are nonetheless able to successfully integrate cannabis use into everyday life with few associated problems. Indeed, our findings advocate that regular use of small amounts of cannabis does not appear to increase an individual’s likelihood of experiencing problems, and it does not threaten one’s ability to function well and perform expected roles. Even so, the tools used to assess potentially harmful cannabis use invariably serve to classify almost all ‘regular’ users as problematic users."

"To provide a sense of the intensity of enforcement, we calculated the risk a marijuana user faces of being arrested for possession. If calculated per joint consumed, the figure nationally is trivial—perhaps one arrest for every 11,000–12,000 joints.⁴ However, the relevant risk may be the probability of being arrested during a year of normal consumption. Since marijuana is mostly consumed by individuals who use it at least once a month,⁵ we estimated the risk that such individuals face. We know from prior studies (e.g., Reuter, Hirschfield, and Davies, 2001) that these risks are higher for youth. Table 2.2 presents separate estimates for those aged 12–17 and for the entire population 12 and over. We observe that the annual risk of misdemeanor arrest for those 12–17 (6.6 percent) is more than twice the rate for the full population (3.0 percent)."

"In sum, these findings run counter to arguments suggesting the legalization of marijuana for medical purposes poses a danger to public health in terms of exposure to violent crime and property crimes. To be sure, medical marijuana laws were not found to have a crime exacerbating effect on any of the seven crime types. On the contrary, our findings indicated that MML precedes a reduction in homicide and assault. While it is important to remain cautious when interpreting these findings as evidence that MML reduces crime, these results do fall in line with recent evidence [29] and they conform to the longstanding notion that marijuana legalization may lead to a reduction in alcohol use due to individuals substituting marijuana for alcohol [see generally 29, 30]. Given the relationship between alcohol and violent crime [31], it may turn out that substituting marijuana for alcohol leads to minor reductions in violent crimes that can be detected at the state level. That said, it also remains possible that these associations are statistical artifacts (recall that only the homicide effect holds up when a Bonferroni correction is made)."

" A recent issue of The DASIS Report² examined marijuana treatment admissions between 1992 and 2002 and found that between these years [1992 and 2002] the rate of substance abuse treatment admissions reporting marijuana as their primary substance of abuse³ per 100,000 population increased 162 percent. Similarly, the proportion of marijuana admissions increased from 6 percent of all admissions in 1992 to 15 percent of all admissions reported to the Treatment Episode Data Set (TEDS) in 2002.
"During this time period, the percentage of marijuana treatment admissions that were referred from the criminal justice system increased from 48 percent of all marijuana admissions in 1992 to 58 percent of all marijuana admissions in 2002."

"Although marijuana grown in the United States was once considered inferior because of a low concentration of THC, advancements in plant selection and cultivation have resulted in higher THC-containing domestic marijuana. In 1974, the average THC content of illicit marijuana was less than one percent. Today most commercial grade marijuana from Mexico/Columbia and domestic outdoor cultivated marijuana has an average THC content of about 4 to 6 percent. Between 1998 and 2002, NIDA-sponsored Marijuana Potency Monitoring System (MPMP) analyzed 4,603 domestic samples. Of those samples, 379 tested over 15 percent THC, 69 samples tested between 20 and 25 percent THC and four samples tested over 25 percent THC."

"California, Hawaii, Kentucky, Oregon, Tennessee, Washington, and West Virginia are the primary marijuana cultivation states (M7 states). Domestic Cannabis Eradication/Suppression Program (DCE/SP) data show that more than 8 million plants were eradicated in 2008, 89 percent (7,136,133 plants of 8,013,308 plants) of which were eradicated in the M7 States."

Click here for complete datatable of THC Potency of Tested Cannabis from Federal Seizure and State and Local Eradication Samples, by Type, 1985-2014.

"Data on the THC content of cannabis products in the USA have been collected by ElSohly et al. (1984, 2000) for many years as part of the University of Mississippi Potency Monitoring Project. Samples were submitted by law enforcement agencies and it has to be assumed that they were representative of the market. Mean THC values are shown in Figure 16 for normal herbal cannabis, sinsemilla and resin. The anomalously high value for resin in 1997 (19.24 %) has been excluded; it was based on only five values and is over nine standard deviations above the mean potency for the period 1980–1996. Although there has been an increase in the potency of herbal cannabis over the twenty-five-year period, cannabis resin (and hash oil) showed no long-term trends since 1980 when data were first collected. Although the potency of sinsemilla showed a clear upward trend in the final three years of the study, no such trend was obvious when the longer period of 1980–1995 is examined, particularly in view of the wide variations in potency that occurred from year to year (ElSohly et al., 2000). The THC content of herbal cannabis increased from around 1% before 1980 to around 4% in 1997. This increase, when seen in the European context, is deceptive. Before 1980, all mean herbal cannabis THC levels in the ElSohly study were less than 2.4%. By contrast, and as shown in Figure 10, comparable levels at that time in the United Kingdom were twice as great. In other words, it must be assumed that the quality of herbal cannabis consumed in the USA more than twenty years ago was unusually poor, but that in recent years it has risen to levels typical of Europe. So even the modest increase found by ElSohly et al. (2000) may be less significant than it seems. A recent analysis of cannabis seized in Florida in 2002 (Newell, 2003) showed amounts of THC found in samples ranging from 1.41% to 12.62%; the average THC content was 6.20%, which is almost identical to the 2002 value reported by the University of Mississippi Potency Monitoring Project."

"Despite continuing increases in the amount of cannabis produced domestically, much of the marijuana available within the United States is foreign-produced. The two primary foreign source areas for marijuana distributed within the United States are Canada and Mexico. Mexican drug trafficking organizations (DTOs) have relocated many of their outdoor cannabis cultivation operations in Mexico from traditional growing areas to more remote locations in central and northern Mexico, primarily to reduce the risk of eradication and gain easier access to U.S. drug markets. Asian criminal groups are the primary producers of high-potency marijuana in Canada."

"There are health risks of cannabis use, most particularly when it is used daily over a period of years or decades. Considerable uncertainty remains about whether these effects are attributable to cannabis use alone, and about what the quantitative relationship is between frequency, quantity and duration of cannabis use and the risk of experiencing these effects.
"On existing patterns of use, cannabis poses a much less serious public health problem than is currently posed by alcohol and tobacco in Western societies."

"The public health burden of cannabis use is probably modest compared with that of alcohol, tobacco, and other illicit drugs. A recent Australian study⁹⁶ estimated that cannabis use caused 0·2% of total disease burden in Australia—a country with one of the highest reported rates of cannabis use. Cannabis accounted for 10% of the burden attributable to all illicit drugs (including heroin, cocaine, and amphetamines). It also accounted for around 10% of the proportion of disease burden attributed to alcohol (2·3%), but only 2·5% of that attributable to tobacco (7·8%)."

"A careful search of the literature and testimony of the nation's health officials has not revealed a single human fatality in the United States proven to have resulted solely from ingestion of marihuana. Experiments with the drug in monkeys demonstrated that the dose required for overdose death was enormous and for all practical purposes unachievable by humans smoking marihuana. This is in marked contrast to other substances in common use, most notably alcohol and barbiturate sleeping pills."

"For physiological and pharmacological reasons,⁶¹ smoking cannabinoid herbals does not seem to have a similar health hazard profile as tobacco smoking, aside from the potential for bronchial irritation and bronchitis. Smoking cannabis was not associated with an increased risk of developing chronic obstructive pulmonary disease ..."

"Despite these findings, the small number of observational studies fail to demonstrate a clear association between marijuana smoking and diagnoses of lung cancer. Therefore, we must conclude that no convincing evidence exists for an association between marijuana smoking and lung cancer based on existing data. Nonetheless, certain logistic properties of marijuana smoking may increase the risk of carcinogenic exposure compared with conventional tobacco smoking, raising questions as to why observational studies have not demonstrated an association with lung cancer."

"Nonetheless, and contrary to our expectations, we found no positive associations between marijuana use and lung or UAT cancers. Although we observed positive dose-response relations of marijuana use to oral and laryngeal cancers in the crude analyses, the trend was no longer observed when adjusting for potential confounders, especially cigarette smoking. In fact, we observed ORs <1 for all cancers except for oral cancer, and a consistent monotonic association was not apparent for any outcome. Similar findings were found when the analyses were restricted to subjects who never smoked cigarettes. The 95% confidence intervals for the adjusted ORs did not extend far above 1 (e.g., were under 2 for marijuana and lung cancer), which suggests that associations of marijuana use with the study cancers are not strong and may be below detectable limits for this type of study."

"In the current study, we demonstrated that chronic cannabis smokers had relative visceral adiposity and adipose tissue insulin resistance but not hepatic steatosis, glucose insulin insensitivity, impaired pancreatic b-cell function, glucose intolerance, or dyslipidemia compared with age-, sex-, ethnicity-, and BMI-matched control individuals. Our study results suggest that chronic, daily cannabis use may have differential tissue-specific effects on insulin sensitivity, but these effects appear to have minimal impact on glucose or lipid metabolism."

Marijuana use is associated with higher daily caloric intake. In the NHANES III and CARDIA study, heavy cannabis users had ;20% higher calorie intake than nonusers (25,26). The increase in calories was from higher intake of all macronutrients. Specifically, the frequency and amount of consumption of soda, cheese, salty snacks, pork, and alcohol was higher in cannabis users. Consistent with other studies, the quality of diets consumed by cannabis users was poor (27). Furthermore, the percent of daily calories derived from carbohydrates relatively rich in simple sugars was significantly higher in marijuana smokers. These findings are consistent with human and animal studies demonstrating that cannabinoids stimulate food intake, specifically highly palatable sweet-tasting foods (28). Cannabis smokers in our study exhibited characteristics typically observed in marijuana smokers in the general population."

"As research on pharmacological treatments for CUD continues, a few key findings are of note. First, cannabinoid agonists (nabilone, dronabinol in combination with lofexidine, and lofexidine alone), were the only drugs that decreased drug-taking in a human laboratory model of relapse, supporting the notion that agonist replacement and attenuation of noradrenergic activity show promise for relapse prevention. Although dronabinol alone failed to clinically reduce cannabis use, a higher dose might have been more effective. Further, that study was designed to evaluate the initiation of abstinence; dronabinol or the more bioavailable agonist nabilone, might have greater utility in the prevention of relapse [25•]. These studies also support further testing of lofexidine in combination with other drugs, and generally illustrate the utility that can be gained from combining medications.
"Second, gabapentin and NAC were the only drugs tested in placebo-controlled clinical trials that decreased cannabis use (abstinence induction). Third, the ability of a drug to reduce cannabis withdrawal symptoms is not predictive of its ability to alter drug-taking behaviors (reduce use or prevent relapse). However, all the studies that reported positive changes in drug use also reported a reduction in withdrawal during early abstinence, suggesting that this feature is an important component of an efficacious medication."

"Analysis of the demographic and social characteristics of a large sample of applicants seeking approval to use marijuana medically in California supports an interpretation of long term non problematic use by many who had first tried it as adolescents, and then either continued to use it or later resumed its use as adults. In general, they have used it at modest levels and in consistent patterns which anecdotally-often assisted their educational achievement, employment performance, and establishment of a more stable life-style. These data suggest that rather than acting as a gateway to other drugs, (which many had also tried), cannabis has been exerting a beneficial influence on most."

"This study among 98 experienced cannabis smokers is the first naturalistic study to examine whether users of cannabis with high THC concentration titrate the psychoactive effects by using lower doses and/or by reduced inhalation, and whether cannabis smoking behaviour (topography) predicts cannabis dependence severity independently of total THC exposure.
"In contrast to our hypothesis, there was a positive association between cannabis THC concentration and cannabis dose, indicating that users of stronger cannabis generally used larger amounts of cannabis to prepare their regular joint. However, in line with our hypothesis, the negative association between THC concentration of joints and total inhaled smoke volume indicates that users of stronger joints inhaled smaller smoke volumes, thus resulting in partial titration of the total THC exposure. Overall, as exemplified by the comparison of the average user with the user with the maximum THC concentration, users of high-potency cannabis will generally be exposed to higher total doses of THC (at least in this sample). This is in line with Cappell et al.’s observations through a one-way mirror experiment in 1973 where users only partly adapted their intake [14]. Indeed, increased THC concentrations of cannabis have recently been linked to increased internal THC exposure assessed in blood [28]."

"The withdrawal syndrome associated with dronabinol, the API [Active Pharmaceutical Ingredient] in Marinol®, produces symptoms in humans such as restlessness, irritability, mild agitation, anxiety, anger, insomnia, sleep EEG disturbances, nausea, decreased appetite, and decreased weight. Since a withdrawal syndrome is indicative of physical dependence, it is reasonable to conclude that generic dronabinol products (both naturally-derived [from the cannabis plant] or synthetically produced, and in hard or soft gelatin capsules) in sesame oil, will also produce physical dependence similar to those produced by Marinol®."

"There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other illicit drugs."

"In line with previous work, we found that cannabis users had lower teenage IQ scores and poorer educational performance than teenagers who had never used cannabis. At the same time, cannabis users also had higher rates of childhood behavioural problems, childhood depressive symptoms, other substance use (including use of cigarettes and alcohol) and maternal use of cannabis during pregnancy. After adjustment to account for these group differences, cannabis use by the age of 15 did not predict either lower teenage IQ scores or poorer educational performance. These findings therefore suggest that cannabis use at the modest levels used by this sample of teenagers is not by itself causally related to cognitive impairment. Instead, our findings imply that previously reported associations between adolescent cannabis use and poorer intellectual and educational outcomes may be confounded to a significant degree by related factors."

"Compared with those in our sample who had never tried cannabis, teenagers who had used cannabis at least 50 times were 17 times more likely (84% vs. 5%) to have smoked cigarettes more than 20 times in their lifetime. Accounting for group differences in cigarette smoking dramatically attenuated the associations between cannabis use and both IQ and educational performance. Further, even after excluding those who had never tried cannabis, cigarette users were found to have lower educational performance (adjusted performance 2.9 percentage points lower, approximately equivalent to dropping two grades on one subject taken at GCSE) relative to those who had never tried cigarettes. A relationship between cigarette use and poorer cognitive (Chamberlain et al., 2012; Hooper et al., 2014; Weiser et al., 2010; Whalley et al., 2005) and educational (McCaffrey et al., 2010; Silins et al., 2014; Stiby et al., 2014) outcomes has been noted previously, and may have a number of explanations. Cigarette use may have a negative impact on cognitive ability. However, this is not supported by the experimental psychopharmacology literature, which robustly shows that acute nicotine administration results in transient cognitive enhancement (Heishman et al., 2010). Alternatively, reverse causality may contribute to this relationship, for example performing poorly at school may lead to increased engagement in risky behaviours such as cigarette smoking. Further, residual confounding may contribute to this link: cigarette smoking may be a marker of unmeasured factors, for example social adversity during adolescence, that influence both IQ and educational attainment."

"Although the heavy current users experienced a decrease in IQ score, their scores were still above average at the young adult assessment (mean 105.1). If we had not assessed preteen IQ, these subjects would have appeared to be functioning normally. Only with knowledge of the change in IQ score does the negative impact of current heavy use become apparent."

"Nevertheless, when considering all 15 studies (i.e., those that met both strict and more relaxed criteria) we only noted that regular cannabis users performed worse on memory tests, but that the magnitude of the effect was very small. The small magnitude of effect sizes from observations of chronic users of cannabis suggests that cannabis compounds, if found to have therapeutic value, should have a good margin of safety from a neurocognitive standpoint under the more limited conditions of exposure that would likely obtain in a medical setting."

"The results of our meta-analytic study failed to reveal a substantial, systematic effect of long-term, regular cannabis consumption on the neurocognitive functioning of users who were not acutely intoxicated. For six of the eight neurocognitive ability areas that were surveyed. the confidence intervals for the average effect sizes across studies overlapped zero in each instance, indicating that the effect size could not be distinguished from zero. The two exceptions were in the domains of learning and forgetting."

"Other studies have found short term residual effects of cannabis use on memory and cognition (34, 35) that are more severe among women (36) and heavy users (37). However, our data suggest that over the long term cannabis use is not associated with greater declines in cognition among men, women, or heavy users. The study design we used included several of the features proposed by Pope et al. (34) as critical to addressing the long term effects of cannabis on cognition: naturalistic follow-up, a large sample size, a population basis, comparison of light cannabis use with heavy use, and the construction of models accounting for the effects of gender and use of illicit drugs, alcohol, and tobacco. Therefore, these results would seem to provide strong evidence of the absence of a long term residual effect of cannabis use on cognition."

"The [endo] cannabinoids produce psychological states that closely parallel several experiences described as being related to the runner’s high. Compared with the opioid analgesics, the analgesia produced by the endocannabinoid system is more consistent with exercise induced analgesia. Activation of the endocannabinoid system also produces sedation, anxiolysis, a sense of wellbeing, reduced attentional capacity, impaired working memory ability, and difficulty in time estimation. This behavioural profile is similar to the psychological experiences reported by long distance runners."

"This 10 year follow-up study showed that incident cannabis use significantly increased the risk of incident psychotic experiences. The association was independent of age, sex, socioeconomic status, use of other drugs, urban/rural environment, and childhood trauma; additional adjustment for other psychiatric diagnoses similarly did not change the results. There was no evidence for self medication effects as psychotic experiences did not predict later cannabis use. The results thus help to clarify the temporal association between cannabis use and psychotic experiences by systematically addressing the issue of reverse causality, given that the long follow-up period allowed exclusion of all individuals with pre-existing psychotic experiences or pre-existing cannabis use. In addition, cannabis use was confirmed as an environmental risk factor impacting on the risk of persistence of psychotic experiences (fig 3)."

"In terms of the model set out in the Introduction, the expected rise in diagnoses of schizophrenia and psychoses did not occur over a 10 year period. This study does not therefore support the specific causal link between cannabis use and the incidence of psychotic disorders based on the 3 assumptions described in the Introduction. This concurs with other reports indicating that increases in population cannabis use have not been followed by increases in psychotic incidence (Macleod et al., 2006; Arsenault et al., 2004; Rey and Tennant, 2002). However, it is not in line with findings of a rise in first admission rates for psychotic disorders among young people in Zurich following increases in cannabis availability and consumption (Ajdacic-Gross et al., 2007). One factor involved in this discrepancy may be the potency of the cannabis consumed, which varies considerably within Europe (EMCDDA, 2008). In addition, a Netherlands study found that high-potency cannabis obtained from ‘coffee shops’ led to higher levels of tetrahydrocannabinol (THC) in the blood, with young males aged 18–45 at particular risk for excessive consumption (Mensinga et al., 2006)."

"First, the use of cannabis and rates of psychotic symptoms were related to each other, independently of observed/non-observed fixed covariates and observed time dynamic factors (Table 2). Secondly, the results of structural equation modeling suggest that the direction of causation is that the use of cannabis leads to increases in levels of psychotic symptoms rather than psychotic symptoms increasing the use of cannabis. Indeed, there is a suggestion from the model results that increases in psychotic symptoms may inhibit the use of cannabis."

"Laboratory studies also find no link between THC intoxication and violence. Most people who ingest THC before performing a competitive task in the laboratory do not show more aggression than people who receive placebos; occasionally they show decreased hostility. Numerous scientific panels sponsored by various governments invariably report that marijuana does not lead to violence.(751)"

"Annual marijuana prevalence peaked among 12th graders in 1979 at 51%, following a rise that began during the 1960s. Then use declined fairly steadily for 13 years, bottoming at 22% in 1992—a decline of more than half. The 1990s, however, saw a resurgence of use. After a considerable increase (one that actually began among 8th graders a year earlier than among 10th and 12th graders), annual prevalence rates peaked in 1996 at 8th grade and in 1997 at 10th and 12th grades. After these peak years, use declined among all three grades through 2007 or 2008. After these declines, an upturn occurred in use in all three grades, lasting for three years in the lower grades and longer in grade 12. Annual marijuana prevalence among 8th graders increased in use from 2007 to 2010, decreased slightly from 2010 to 2012, and then declined significantly in 2016. Among 10th graders, use increased somewhat from 2008 to 2013 and then declined after that. Among 12th graders, use increased from 2006 to 2011 and then held level through 2016. As shown in Table 8, daily use increased in all three grades after 2007, reaching peaks in 2011 (at 1.3% in 8th), 2013 (at 4.0% in 10th), and 2011 (at 6.6% in 12th), before declining slightly since. Daily prevalence rates in 2016 were 0.7%, 2.5%, and 6.0%, respectively, with one in seventeen 12th graders smoking daily."

"Teens also say they are seeing more peers in school smoking marijuana and more teens (73 percent) report having friends who smoke marijuana regularly (71 percent) – significantly higher than four years ago. Since 2008, there have also been significant declines in teen perceptions that they will lose respect, harm themselves, or mess up their lives if they use marijuana."

"The proportion of students seeing great risk from using marijuana regularly fell during the rise in use in the 1970s, and again during the subsequent rise in the 1990s. Indeed, at 10th and 12th grades, perceived risk declined a year before use rose in the upturn of the 1990s, making perceived risk a leading indicator of change in use. (The same may have happened at 8th grade as well, but we lack data starting early enough to know.) The decline in perceived risk halted in 1996 in 8th and 10th grades; the increases in use ended a year or two later, again making perceived risk a leading indicator. From 1996 to 2000, perceived risk held fairly steady and the decline in use in the upper grades stalled. After some decline prior to 2002, perceived risk increased in all grades through 2004 as use decreased. Perceived risk fell after 2004 and 2005 in 8th and 12th grades respectively, (and since 2008 in 10th grade) presaging the more recent increase in use. In 2011 perceived risk continued to decline in grades 10 and 12 and leveled in grade 8."

"The apparent strength of these relationships in cross-sectional studies (e.g. Kandel, 1984) has been exaggerated because those adolescents who are most likely to use cannabis have lower academic aspirations and poorer high school performance prior to using cannabis than their peers who do not (Newcombe and Bentler, 1988). It remains possible that factors other than the marijuana use account for apparent causal relations. To the extent they may exist, these adverse effects of cannabis and other drug use upon development over and above the effect of pre-existing nonconformity may cascade throughout young adult life, affecting choice of occupation, level of income, choice of mate, and the quality of life of the user and his or her children."

"As with cannabis, alcohol use increased variability in lane position and headway (Casswell, 1979; Ramaekers et al., 2000; Smiley et al., 1981; Stein et al., 1983) but caused faster speeds (Casswell, 1977; Krueger & Vollrath, 2000; Peck et al., 1986; Smiley et al., 1987; Stein et al., 1983). Some studies also showed that alcohol use alone and in combination with cannabis affected visual search behavior (Lamers & Ramaekers, 2001; Moskowitz, Ziedman, & Sharma, 1976). Alcohol consumption combined with cannabis use also worsened driver performance relative to use of either substance alone. Lane position and headway variability were more exaggerated (Attwood et al., 1981; Ramaekers et al., 2000; Robbe, 1998) and speeds were faster (Peck et al., 1986).
"Both simulator and road studies showed that relative to alcohol use alone, participants who used cannabis alone or in combination with alcohol were more aware of their intoxication. Robbe (1998) found that participants who consumed 100 g/kg of cannabis rated their performance worse and the amount of effort required greater compared to those who consumed alcohol (0.05 BAC). Ramaekers et al. (2000) showed that cannabis use alone and in combination with alcohol consumption increased self-ratings of intoxication and decreased self-ratings of performance. Lamers and Ramaekers (2001) found that cannabis use alone (100 g/kg) and in combination with alcohol consumption resulted in lower ratings of alertness, greater perceptions of effort, and worse ratings of performance."

"Overall, 23,591 (90.9%) of the 25,951 drivers who died within 1 hour of a crash in these 6 states underwent toxicological testing. Drivers who were tested for drugs were similar in crash circumstances to those who were not tested, but they appeared to be slightly younger (mean age = 39.4 (standard deviation, 19.4) years vs. 43.4 (standard deviation, 27.7) years), more likely to be male (77.7% vs. 75.8%), more likely to be involved in nighttime crashes (51.4% vs. 47.0%), and more likely to have been involved in a crash in the previous 3 years (15.7% vs. 13.9%) than those who were not tested.
"Of the 23,591 drivers tested, 39.7% were positive for alcohol, and 24.8% tested positive for other drugs. The prevalence of alcohol involvement was stable at approximately 39% from 1999 to 2010 (Z = ?1.4, P = 0.16). Alcohol involvement was more prevalent in men (43.6%) than in women (26.1%), but trends were stable for both sexes (Table 1). In contrast, the prevalence of nonalcohol drugs showed a statistically significant increasing trend over the study period, rising from 16.6% (95% confidence interval (CI): 14.8, 18.4) in 1999 to 28.3% (95% CI: 26.0, 30.7) in 2010 (Z = ?10.19, P < 0.0001). The prevalence rates of non-alcohol drugs and 2 or more nonalcohol drugs increased significantly over the study period in both sexes (Table 1). The prevalence of nonalcohol drug use increased significantly across all age groups (Figure 1)."

"The prevalence of drugs detected in cases was higher than in controls across the drug categories (Table 3). Marijuana, narcotics, stimulants, and depressants were each associated with a significantly increased risk of fatal crash involvement, with estimated odds ratios ranging from 1.83 for marijuana to 4.83 for depressants (Table 3). Polydrug use, defined as use of two or more non-alcohol drugs, was associated with a 3.4-fold increased risk of fatal crash involvement (Table 3).
"About one-fifth (20.5%) of the cases tested positive for alcohol and one or more drugs, compared with 2.2% of the controls. Relative to drivers who tested positive for neither alcohol nor drugs, the estimated odds of fatal crash involvement increased over 13 folds for those who were alcohol-positive but drug-negative, more than two folds for those who were alcohol-negative but drug-positive, and 23 folds for those who were positive for both alcohol and drugs (Table 4)."

"Absorption is slower following the oral route of administration with lower, more delayed peak THC levels. Bioavailability is reduced following oral ingestion due to extensive first pass metabolism. Smoking marijuana results in rapid absorption with peak THC plasma concentrations occurring prior to the end of smoking. Concentrations vary depending on the potency of marijuana and the manner in which the drug is smoked, however, peak plasma concentrations of 100-200 ng/mL are routinely encountered. Plasma THC concentrations generally fall below 5 ng/mL less than 3 hours after smoking. THC is highly lipid soluble, and plasma and urinary elimination half-lives are best estimated at 3-4 days, where the rate-limiting step is the slow redistribution to plasma of THC sequestered in the tissues. Shorter half-lives are generally reported due to limited collection intervals and less sensitive analytical methods. Plasma THC concentrations in occasional users rapidly fall below limits of quantitation within 8 to 12 h. THC is rapidly and extensively metabolized with very little THC being excreted unchanged from the body. THC is primarily metabolized to 11-hydroxy-THC which has equipotent psychoactivity. The 11-hydroxy-THC is then rapidly metabolized to the 11-nor-9-carboxy-THC (THC-COOH) which is not psychoactive. A majority of THC is excreted via the feces (~65%) with approximately 30% of the THC being eliminated in the urine as conjugated glucuronic acids and free THC hydroxylated metabolites."

"Cannabis use impairs cognitive, memory and psycho-motor performance in ways that may impair driving.¹⁰ Recent data suggest that approximately 5% of Canadian drivers/adults report driving after cannabis use in the past year.³⁹ Large-scale epidemiological studies using different methodologies (e.g., retrospective epidemiological and case control studies) have found that cannabis use acutely increases the risk of motor vehicle accident (MVA) involvement and fatal crashes among drivers.^40,41 Recent reviews have found the increase in risk to be approximately 1.5-3.0, an increase which is substantially lower, however, than that in alcohol-impaired drivers. The impairment from concurrent alcohol and cannabis use may be multiplicative, so individuals who drive under the influence of both drugs may be at higher risk for MVAs.⁴² An expert consensus view was that a THC concentration of 7-10 nanograms per millilitre in serum would produce impairment equivalent to that of 0.05% blood alcohol content (BAC). It was suggested that this level could serve as a 'per se' limit to define cannabis-impaired driving.⁴³ Current research suggests that acute impairment from cannabis typically clears 3-4 hours after use.⁴⁴
"This time span could be recommended to users as a minimum wait period before driving. The required wait before driving would need to be longer for higher doses, and would also vary on the basis of individual variation."

"There is considerable evidence from laboratory studies that cannabis (marijuana) impairs reaction time, attention, tracking, hand-eye coordination, and concentration, although not all of these impairments were equally detected by all studies (Couper & Logan, 2004a; Heishman, Stitzer, & Yingling, 1989; Gieringer, 1988; Moskowitz, 1985). In reviewing the literature on marijuana, Smiley (1998) concluded that marijuana impairs performance in divided attention tasks (i.e., a poorer performance on subsidiary tasks). Jones et al. (2003) adds that Smiley’s finding is relevant to the multitasking essence of driving, in particular by making marijuana impaired drivers perhaps less able to handle unexpected events. Interestingly, there is also evidence showing that, unlike alcohol, marijuana enhances rather than mitigates the individual’s perception of impairment (Lamers & Ramaekers, 1999; Robbe & O'Hanlon, 1993; Perez-Reyes, Hicks, Bumberry, Jeffcoat, & Cook, 1988). Robbe and O'Hanlon (1993) reported that in laboratory conditions, drivers under the influence of marijuana were aware of their impairment, which led them to decrease speed, avoid passing other vehicles, and reduce other risk-taking behaviors. Such was not the case with alcohol; for the authors reported that alcohol-impaired drivers were generally not aware of impairment, and therefore did not adjust their driving accordingly."

"Participants receiving active marijuana decreased their speed more so than those receiving the placebo cigarette during a distracted section of the drive, An overall effect of marijuana was seen for the mean speed during the distracted driving (PASAT [Paced Auditory Serial-Addition Test] section), While no other changes in driving performance were found, marijuana appeared to hinder practice effects on the PASAT task, suggesting individuals may not be able to adequately use information and experience previously acquired while under the influence of marijuana, While only minimal differences in driving performance were found, this failure to benefit from prior practice may be detrimental to driving performance. Research has shown that graduated driver's licensing programs in which participants receive more on the road training results in a decrease in fatal crashes in 16-year-olds (Baker, Chen & Li 2006), If marijuana indeed impairs one's ability to use prior experience to improve performance, this will likely impair driving under pretrained conditions (e,g,, steering into a skid, allowing increased stopping time on slippery roads, etc)."

"The decreased speed during the simulated drive could be interpreted as an attempt to compensate for perceived cognitive impairment, Alternatively, marijuana may not have affected decision making and judgment and the reduction in speed would improve safety margins, While the clinical significance of a 3% to 5% decrease in speed may be questioned, previous research suggests such a decrease will result in approximately a 7% decrease in all injuries and a 15% decrease in fatalities (Nilsson 1981), Use of an alternate task design in which subjects are requested to drive as quickly and as safely as possible rather than following a posted speed limit may provide more insight into compensatory strategies employed while driving under the influence of marijuana, Use of a more challenging road paradigm (e.g., icy or gravel roads) which capitalizes on the use of practice effects may aid in identifying differences in driving performance under the influence of marijuana, There was significant between-subject variability in driving measures and future studies would be further strengthened by using a within-subjects design."

"When compared to alcohol, cannabis is detected far less often in accident-involved drivers. Drummer et al. (2003) cited several studies and found that alcohol was detected in 12.5% to 79% of drivers involved in accidents. With regard to crash risk, a large study conducted by Borkenstein, Crowther, Shumate, Zeil and Zylman (1964) compared BAC in approximately 6,000 accident-involved drivers and 7,600 nonaccident controls. They determined the crash risk for each BAC by comparing the number of accident-involved drivers with detected levels of alcohol at each BAC to the number of nonaccident control drivers with the same BAC. They found that crash risk increased sharply as BAC increased. More specifically, at a BAC of 0.10, drivers were approximately five times more likely to be involved in an accident.
"Similar crash risk results were obtained when data for culpable drivers were evaluated. Drummer (1995) found that drivers with detected levels of alcohol were 7.6 times more likely to be culpable. Longo et al. (2000) showed that drivers who tested positive for alcohol were 8.0 times more culpable, and alcohol consumption in combination with cannabis use produced an odds ratio of 5.4. Similar results were also noted by Swann (2000) and Drummer et al. (2003)."

"Most of the research on cannabis use has been conducted under laboratory conditions. The literature reviews by Robbe (1994), Hall, Solowij, and Lemon (1994), Border and Norton (1996), and Solowij (1998) agreed that the most extensive effect of cannabis is to impair memory and attention. Additional deficits include problems with temporal processing, (complex) reaction times, and dynamic tracking. These conclusions are generally consistent with the psychopharmacological effects of cannabis mentioned above, including problems with attention, memory, motor coordination, and alertness.
"A meta-analysis by Krüger and Berghaus (1995) profiled the effects of cannabis and alcohol. They reviewed 197 published studies of alcohol and 60 studies of cannabis. Their analysis showed that 50% of the reported effects were significant at a BAC of 0.073 g/dl and a THC level of 11 ng/ml. This implies that if the legal BAC threshold for alcohol is 0.08 g/dl, the corresponding level of THC that would impair the same percentage of tests would be approximately 11 ng/ml."

"Both simulator and road studies showed that relative to alcohol use alone, participants who used cannabis alone or in combination with alcohol were more aware of their intoxication. Robbe (1998) found that participants who consumed 100 g/kg of cannabis rated their performance worse and the amount of effort required greater compared to those who consumed alcohol (0.05 BAC). Ramaekers et al. (2000) showed that cannabis use alone and in combination with alcohol consumption increased self-ratings of intoxication and decreased self-ratings of performance. Lamers and Ramaekers (2001) found that cannabis use alone (100 g/kg) and in combination with alcohol consumption resulted in lower ratings of alertness, greater perceptions of effort, and worse ratings of performance."

"In conclusion, cannabis impairs driving behaviour. However, this impairment is mediated in that subjects under cannabis treatment appear to perceive that they are indeed impaired. Where they can compensate, they do, for example, by not overtaking, by slowing down and by focusing their attention when they know a response will be required. However, such compensation is not possible where events are unexpected or where continuous attention is required. Effects of driving behaviour are present up to an hour after smoking but do not continue for extended periods."
"Thus, not only is it problematic to estimate the percentage of accident involvements associated with cannabis use alone, there is no evidence that impairment resulting from cannabis use causes accidents. Attempts to alleviate these problems by calculating risk of culpability for an accident (rather than the risk of having an accident) suggest that cannabis may actually reduce responsibility for accidents."

"Based on the research to date, the harms associated with the actual use of cannabis likely pale in comparison with the widely observed harms attributable to cannabis prohibition. As such, policymakers should integrate the scientific research conducted on the likely impacts of current prohibitive approaches to cannabis use into the process of optimising cannabis policy."

"There is no evidence that the depenalization component of the 1976 policy, per se, increased levels of cannabis use. On the other hand, the later growth in commercial access to cannabis, after de facto legalization, was accompanied by steep increases in use, even among youth. In interpreting that association, three points deserve emphasis. First, the association may not be causal; we have already seen that recent increases occurred in the United States and Oslo despite very different policies. Second, throughout most of the first two decades of the 1976 policy, Dutch use levels have remained at or below those in the United States. And third, it remains to be seen whether prevalence levels will drop again in response to the reduction to a 5-g limit, and to recent government efforts to close down coffee shops and more aggressively enforce the regulations."

"In California and Ohio, surveys before and after decriminalisation showed that cannabis use increased, but not at a greater rate than in US states which had not decriminalised cannabis. Single (1989) also reviewed data from two large US national surveys of drug use in the 1970s that compared rates of cannabis use in states which had and had not decriminalised cannabis. He found that the prevalence of cannabis use increased in all states, with a larger increase in those states which had not decriminalised (Single, 1989)."

"... the Government of Canada amend the Controlled Drugs and Substances Act to create a criminal exemption scheme. This legislation should stipulate the conditions for obtaining licenses as well as for producing and selling cannabis; criminal penalties for illegal trafficking and export; and the preservation of criminal penalties for all activities falling outside the scope of the exemption scheme."

"Rather than inducing violent or aggressive behavior through its purported effects of lowering inhibitions, weakening impulse control and heightening aggressive tendencies, marihuana was usually found to inhibit the expression of aggressive impulses by pacifying the user, interfering with muscular coordination, reducing psychomotor activities and generally producing states of drowsiness lethargy, timidity and passivity."

"Proponents of criminalization attribute to their preferred drug-control regime a special power to affect user behavior. Our findings cast doubt on such attributions. Despite widespread lawful availability of cannabis in Amsterdam, there were no differences between the 2 cities [Amsterdam and San Francisco] in age at onset of use, age at first regular use, or age at the start of maximum use."
"Our findings do not support claims that criminalization reduces cannabis use and that decriminalization increases cannabis use."

"The available evidence suggests that removal of the prohibition against possession itself (decriminalization) does not increase cannabis use. In addition to the Dutch experience from 1976 to 1983, we have similar findings from analysis of weaker decriminalization (with fines retained for the offense of simple possession of small quantities) in 12 US states (Single, 1989) and South Australia and the Australian Capital Territory (Hall, 1997; McGeorge & Aitken, 1997). The fact that Italy and Spain, which have decriminalized possession for all psychoactive drugs, have marijuana use rates comparable to those of neighboring countries provides further support."

"Synthetic cannabinoids are substances chemically produced to mimic tetrahydrocannabinol (THC), the active ingredient in marijuana. When these substances are sprayed onto dried herbs and then consumed through smoking or oral ingestion, they can produce psychoactive effects similar to those of marijuana."

"MTF first addressed the use of synthetic marijuana in its 2011 survey, by asking 12th graders about their use in the prior 12 months (which would have covered a considerable period of time prior to the drugs being scheduled). Annual prevalence was found to be 11.4%, making synthetic marijuana the second most widely used class of illicit drug after marijuana among 12th graders. Despite the DEA’s intervention, use among 12th graders remained unchanged in 2012 at 11.3%, which suggests either that compliance with the new scheduling has been limited or that producers of these products have succeeded in continuing to change their chemical formulas to avoid using the ingredients that have been scheduled. In 2012 for the first time 8th and 10th graders were asked about their use of synthetic marijuana; annual prevalence rates were 4.4% and 8.8%, respectively. Use in all 3 grades dropped in 2013, but the decline was significant only among 12th graders. The 2013 rates were 4.0%, 7.4%, and 7.9% for 8th, 10th, and 12th graders, respectively. Among 8th graders, this was the third highest category of illicit drug being used after marijuana and inhalants."

"Clemson University Professor John Huffman is credited with first synthesizing some of the cannabinoids, such as JWH-018, now used in 'fake pot' substances such as K2. The effects of JWH-018 can be 10 times stronger than those of THC. Dr. Huffman is quoted as saying, 'These things are dangerous—anybody who uses them is playing Russian roulette. They have profound psychological effects. We never intended them for human consumption.'"

"Synthetic marijuana, so named because it contains synthetic versions of some of the cannabinoids found in marijuana, is a recent and important addition to the smorgasbord of drugs available to young people in the US. These designer chemicals are sprayed onto herbal materials that are then sold in small packets under such brand names as Spice and K-2. They have been readily available as over-the-counter drugs on the Internet and in venues like head shops and gas stations. While many of the most widely used chemicals were scheduled by the Drug Enforcement Administration in March of 2011, making their sale no longer legal, purveyors of these products have skirted the restrictions by making small changes in the chemical composition of the cannabinoids used. Use of these products was first measured in MTF in 2011 in a tripwire question for 12th graders, asking about their frequency of use in the prior 12 months (see Table 2-2). Annual prevalence was found to be 11.4%, making synthetic marijuana the second most widely used class of illicit drug after marijuana that year. In spite of the DEA’s scheduling of the most common ingredients, use among 12th graders remained unchanged in 2012, with 11.3% annual prevalence. Eighth and 10th graders were also asked about use of these drugs in 2012, and their annual prevalence levels were 4.4% and 8.8%, respectively, making synthetic marijuana the second most widely used illicit drug among 10th graders, as well, and the third among 8th graders behind marijuana and inhalants. In 2013 use dropped appreciably in all five populations, including statistically significant drops among 12th graders, college students, and young adults. These declines continued in 2014 with significant drops in prevalence among young adults, college students, 12th and 10th graders (a decline among 8th-grade students was not statistically significant). Efforts by the DEA and various states to make their sale illegal may well have had an impact. In 2015 prevalence continued to decline for 8th, 10th, and 12th grade students, although none of the one-year declines were statistically significant. Among young adults and college students prevalence has leveled, with signs of a possible reversal in course with a slight uptick of .2 points (ns) for young adults and .6 (ns) for college students. There is a relatively low level of perceived risk for trying synthetic marijuana once or twice, despite growing evidence of serious problems resulting from the use of these drugs."

"On March 1, 2011, the DEA used its temporary scheduling authority and issued a final rule to place five synthetic cannabinoids on the list of controlled substances under Schedule I of the CSA.26 The five substances are
"• 1-pentyl-3-(1-naphthoyl)indole (JWH-018);
"• 1-butyl-3-(1-naphthoyl)indole (JWH-073);
"• 1-[2-(4-morpholinyl)ethyl]-3-(1-naphthoyl)indole (JWH-200);
"• 5-(1,1-dimethylheptyl)-2-[(1R,3S)-3-hydroxycyclohexyl]-phenol (CP-47,497); and
"• 5-(1,1-dimethyloctyl)-2-[(1R,3S)-3-hydroxycyclohexyl]-phenol (cannabicyclohexanol; CP-47,497 C8 homologue).
"Pursuant to the temporary scheduling authority, these substances will remain on the list of Schedule I controlled substances for one year, and then may be given one six-month temporary extension. To remain on Schedule I thereafter, the substances would need to be permanently scheduled within the CSA."

"There is shared concern among researchers that adding these substances to Schedule I could hinder medical research. As previously mentioned, Professor Huffman did not intend for K2 to be consumed by humans. He is, however, against adding synthetic cannabinoids to Schedule I, asserting that there is still much to learn about synthetic cannabinoids and that placing them on Schedule I would create too many hurdles for researchers who need to access these drugs.⁵⁸ Professor Huffman has created several synthetic cannabinoids that are seen as showing promise in treating skin cancers, pain, and inflammation."

"A dramatic online snapshot of the Spice phenomenon as an emerging trend has been recently given by an important web mapping program, the Psychonaut Web Mapping Project, a European Commission-funded project involving researchers from seven European countries (Belgium, Finland, Germany, Italy, Norway, Spain, and UK), which aims to develop a web scanning system to identify newly marketed psychoactive compounds, and their combinations (e.g., ketamine and Spice, cannabis and Spice), on the basis of the information available on the Internet (Psychonaut Web Mapping Research Group, 2010). As a major result of the Project, a new and updated web-based database is now widely accessible to implement a regular monitoring of the web for novel and recreational drugs."

"There are indications that cannabis was used as early as 4000 B.C. in Central Asia and north-western China, with written evidence going back to 2700 B.C. in the pharmacopeia of emperor Chen-Nong. It then gradually spread across the globe, to India (some 1500 B.C., also mentioned in Altharva Veda, one of four holy books about 1400 B.C.¹), the Near and Middle East (some 900 B.C.), Europe (some 800 B.C.), various parts of South-East Asia (2nd century A.D.), Africa (as of the 11th century A.D.) to the Americas (19th century) and the rest of the world.²"

"The secretion of THC is most abundant in the flowering heads and surrounding leaves. The amount of resin secreted is influenced by environmental conditions during growth (light, temperature and humidity), sex of the plant, and time of harvest. The THC content varies between parts of the plant: from 10-12 % in flowers, 1-2 % in leaves, 0.1-0.3 % in stalks, to less than 0.03 % in the roots."

"The identification of cannabis as a potentially dangerous psychoactive substance did not, however, prevent a substantial number of these enquiries to explore the issue of whether current legislation reflected the real dangers posed by cannabis. Already in 1944, the La Guardia Committee Report on Marihuana concluded that ‘the practice of smoking marihuana does not lead to addiction in the medical sense of the word’ and that ‘the use of marihuana does not lead to morphine or heroin or cocaine addiction’ (Zimmer and Morgan, 1997). In 1968 the Wootton Report stated that ‘the dangers of cannabis use as commonly accepted in the past and the risk of progression to opiates have been overstated’ and ‘cannabis is less harmful than other substances (amphetamines, barbiturates, codeine-like compounds)’. A similar conclusion was arrived at 34 years later in 2002 when the Advisory Committee on Drug Dependence proposed the reclassification of cannabis from Class B to Class C (enforced by law in 2004 and confirmed in 2005). These views were reiterated by other enquiries, such as the Baan Committee in the Netherlands, which affirmed in 1971 that ‘cannabis use does not lead directly to other drug use’ (¹⁶) or by the US National Commission on Marihuana and Drug Abuse, which in 1973 stated that ‘the existing social and legal policy is out of proportion to the individual and social harm engendered by the use of the drug [cannabis]’ (¹⁷). The Canadian Le Dain Commission saw ‘the UN Single Convention of 1961 as responsible’ for such a situation which ‘might have reinforced the erroneous impression that cannabis is to be assimilated to the opiate narcotics’. The same commission, however, suggested that the UN Convention did ‘not prevent domestic legislation from correcting this impression’ (¹⁸)."