In addition to the above, we also identified other factors associated with the occurrence of MA dependence that were shared by men and women including nicotine dependence. Nicotine is a legal drug believed to serve as a gateway for subsequent illegal drug use via both biological and psychosocial mechanisms (Senjo, 2005, Green, 2006, Alegria et al., 2013). ASPD, a more common disorder in males than in females in general (Swanson et al., 1994, Moran, 1999, Grant et al., 2004, Compton et al., 2005, Alegria et al., 2013) and in our sample in specific, has been widely associated with various substance use disorders, including that for MA (Kleinman et al., 1990, Goldstein et al., 2007, Glasner-Edwards et al., 2010, Howard et al., 2010, Yang et al., 2014), especially in institutional settings (Regier et al., 1990). Moreover, substance use in individuals with ASPD was also found to correlate with greater substance-related problems compared to those without ASPD (Westermeyer and Thuras, 2005, Goldstein et al., 2007). Thus, our findings that male MA users had higher prevalence rates of ASPD than female users (17.9%
