"It is estimated that 20 per cent of problem drug users in 2010 received treatment for their drug dependence. Opioids (largely heroin) continue to be the dominant drug type accounting for treatment demand in Asia and Europe (particularly in Eastern Europe and South-Eastern Europe, where they account for almost four out of every five drug users in treatment). Opioids also contribute considerably to demand for treatment in Africa, North America and Oceania. Only in South America is demand for treatment for opioid use negligible (accounting for 1 per cent of all demand for treatment for drug dependence in the region).
"Cannabis, the most widely consumed illicit drug world-wide, is considered to be the least harmful of the illicit drugs. Yet it is the dominant drug accounting for treatment demand in Africa, North America and Oceania, a major contributor to treatment demand in South America and the second most important contributor to such treatment in Europe.
"Treatment for cocaine use is largely associated with the Americas, particularly South America, where it accounts for nearly half of all treatment for illicit drug use, whereas in Asia, Eastern Europe, South-Eastern Europe and Oceania, the share of demand for treatment for drug use accounted for by cocaine use is negligible (less than 1 per cent).
"Demand for treatment for the use of ATS (mostly methamphetamine), is most noticeable in Asia where such drugs are the second major contributor to treatment demand, and to a lesser extent in Oceania, Western and Central Europe and North America."


UN Office on Drugs and Crime, World Drug Report 2012 (United Nations publication, Sales No. E.12.XI.1), pp. 15-16.