One critical issue in follow-up studies is the effect of attrition, i.e. those who participate the baseline assessment but dropout from the follow-up assessment. Such bias would be of great importance if the dropout rate is high, which is not the case in our study. However, we have tested the effect of attrition – i.e. those lost to follow-up as follows: We compared the effects of baseline smoking status and suicide ideation at age 14 according to follow-up participation status as young adult. We found that those who were daily smokers at baseline had lower likelihood for participating the follow-up study at age 22 (OR=0.62, p=0.007). Thus, we acknowledge that there is selective attrition that will bias results; e.g. associations between tobacco use and SRB may actually be under estimations. However, self-reports of suicide ideations at baseline were not associated with follow-up participation status as young adult (p=0.147) and thus that attrition should not bias our findings.
