our results and Lynskey et al.'s (2003) could be related to sampling (e.g., country of residence, age, birth cohort, military service history, gender) and/or methodology (e.g., DSM-III-R vs. DSM-IV). Although Lynskey et al. (2003) found no evidence of gender differences and therefore collapsed their analyses across men and women, it is possible that they were able to do so because they had low power to detect gender differences. Because our analyses included men only, any undetected gender effect in their sample could have led to differences in the results of the two studies. In addition, our respondents were born approximately 15 years before those in the Lynskey et al. (2003) analysis and were about 12 years older at the time of interview, a difference that might be key since secular changes in the acceptability and availability of cannabis occurred between the times that the samples reached peak drug experimentation.
