All WMH surveys used the WHO Composite International Diagnostic Interview, Version 3.0 (Composite International Diagnostic Interview [CIDI] 3.0), a fully structured diagnostic interview for psychiatric conditions [5,6]. Within this assessment, participants were asked if they had ever used (a) alcohol, (b) tobacco (cigarettes, cigars, or pipes), (c) cannabis (marijuana, hashish), and (d) cocaine. Those who had used these drugs were asked about the AOO of use of each drug class, except in New Zealand, Japan, France, Germany, Belgium, the Netherlands, Italy, and Spain, where age of first tobacco smoking was not assessed.
