Prevalence and correlates of illicit and non-medical use of psychotropic drugs in Japan: findings from the World Mental Health Japan Survey 2002-2004.

Purpose: To describe the prevalence of illicit and non-medical use of drugs, the age of first use, and their correlates in the general population of Japan, based on data collected between 2002 and 2004 as part of the World Mental Health (WMH) surveys.

Methods: Participants included were a subsample (n = 887) of the total 2,436 Japanese-speaking respondents aged >or=20 years, randomly sampled from residents in seven cities/municipalities in Japan. Face-to-face household surveys were conducted using the Japanese version of the fully structured WHO WMH Survey Initiative version of the Composite International Diagnostic Interview.

Results: Lifetime prevalence of marijuana and cocaine use, non-medical use of prescribed drugs such as tranquilizers, stimulants and analgesics, and use of other substances was 1.5, 0.3, 6.4 and 2.4%, respectively. Lifetime use of marijuana was significantly greater among men. Prescription drug abuse/misuse was significantly more common among the middle-aged (35-49 years) group and those who were married/cohabitating. The 12-month prevalence of marijuana and non-medical use was 0.3 and 1.9%, respectively. Age of first use was likely to be early adulthood. Non-medical use was significantly related to mood disorder, anxiety disorder, intermittent explosive disorder and alcohol abuse/dependence.

Conclusions: The present study confirmed lower prevalence of drug use in Japan than in other countries, such as the United States. However, the non-medical use of psychotropic drugs seems more common in Japan.