"Contrary to critics’ expectations, available research does not indicate that drug use has skyrocketed in Portugal since decriminalization. Drug use seems to have increased within certain subgroups, and declined within other subgroups. Between 2001 and 2007, lifetime and past-year drug usage slightly increased among Portuguese adults for almost all illicit substances. Conversely, lifetime usage rates slightly declined for teenagers.120 These trends are consistent with drug use trends in Italy and Spain.121 Therefore, changes in drug use in Portugal may reflect regional trends, not changes due to decriminalization.122
"Existing research suggests that there is one significant trend that may be attributed to decriminalization in Portugal. Since Portugal decriminalized drug use in 2001, the prevalence of problematic drug use (“PDU”),123 especially intravenous drug use, has declined.124 This trend is inconsistent with trends in Italy and Spain, where PDU has increased.125 This dissimilarity suggests that decriminalization may have reduced the most harmful forms of drug use in Portugal.126"


Woods, Jordan Blair, "A Decade after Drug Decriminalization: What can the United States learn from the Portugese Model?" University of the District of Columbia Law Review (Washington, DC: The University of the District of Columbia David A. Clarke School of Law, 2011) Volume 15, Number 1, pp. 19-20.