populations have suggested potential differences between men and women. For example, although Brecht et al. (Brecht et al., 2004) found no sex differences in overall residential and outpatient US populations with respect to age of first MA use, they noted that females progressed more quickly to becoming regular users of the drug than males. In a study of Taiwanese MA users in a detention center, Lin et al. (Lin et al., 2004) found that females were significantly younger at the time of first use, a finding the authors suggest might have been explained by military service requirements for men (a duty hypothesized to protect them from illegal drug exposure in late teenage to early adulthood). In contrast to these, we found evidence for an earlier onset of MA in Thai males and comparable rates of progression from use to dependence among males and females. While reasons for these differences are unclear, we hypothesize that our findings may be related to risky behaviors, including sexual behavior as suggested by prior work in adolescent males in Thailand (Ruangkanchanasetr et al., 2005, Liu et al., 2006, Assanangkornchai et al., 2007), the effect of law enforcement focusing on males which could recruit male MA-users
