Based on previous literature (e.g. Dugas et al., 2012; Dumais et al., 2005; Few et al., 2015; Hawton et al., 2003), we considered several variables as potential confounders in the association between tobacco use and SRB. Here, we took into account several baseline variables, namely school achievement, MDD (DSM-IV), impulsivity, and alcohol dependence symptoms, as well as parental education. School achievement was assessed at age 14 when the teachers responded to questionnaire items on school performance, including grade point average (GPA) (Latvala et al., 2014). An adolescent version of the SSAGA (C-SSAGA-A) was used to assess presence or absence of DSM-IV MDD. We assessed impulsivity at age 14 using teacher rating forms of the Multinomial Peer Nomination Inventory (MNPI), which has high reliability, internal consistency and discriminative validity (Pulkkinen et al., 1999). The MPNI covers a wide spectrum of behaviors; the scales for hyperactivity-impulsivity, aggression, and inattention may be used to form a factor for externalizing problem behaviors (Pulkkinen et al., 1999). For our analysis, we utilized the scale for hyperactivity-impulsivity (‘impulsivity’ below). Further, the SSAGA provided diagnoses and symptom
