In the case of early onset of regular tobacco use and suicide ideation, we found no association in males, whereas in females the association was strong and statistically significant. Female vulnerability for SRB has been documented previously in clinical and population samples (Moran et al., 2012). For example, in cross-sectional studies, adolescent female smoking is significantly associated with self-injury, but the association may be non-existent among males (Brunner et al., 2007). A possible explanation for the concurrent and prospective findings may be that the development of nicotine dependence among females after the first use of nicotine may be more rapid than among males. This may be partly explained by sex differences in nicotine metabolism, since among females estrogen is known to enhance metabolism. Also, the anxiolytic effects of nicotine are more pronounced among females (Pogun & Yararbas, 2009). These findings may partially explain the fact that early exposure to tobacco and nicotine may be a more hazardous indicator for subsequent SRB among adolescent females compared to males.
