The mediating effect of depressive symptoms on the relationship between traumatic childhood experiences and drug use initiation.

Stressful experiences such as childhood trauma and depressive symptoms have both been implicated in the initiation of drug use; however, longitudinal designs have not yet been used to elucidate their respective roles to better understand the causal sequence. In the present study, a sensitivity analysis was conducted using two mediation strategies to examine how this sequence may differ by various levels of statistical control, including (1) the standard mediational model in which the effect of lifetime traumatic stressors (Year 1) on the onset of drug use (Years 3 and 4) is mediated by levels of depressive symptoms (Year 2); and (2) a stronger test of causality such that the effect of lifetime traumatic stressors (Year 1) on the onset of drug use (Years 3 and 4) was mediated by changes in depressive symptoms (Year 1 to 2), measured by a residualized change score that controlled for levels in Year 1. Two types of trauma were studied in a community-based study of 489 Hispanic preadolescents (aged 10-12): (a) the number of lifetime traumatic stressors and (b) seven specific lifetime stressors. We also controlled for new onset traumatic stressors occurring between Years 1 and 2. Primary findings indicate that drug use initiation during early adolescence (e.g., ages 14-16) may not be tied to immediate proximal perturbations in risk factors, such as traumatic experiences and depressive symptoms. Rather, the effects of trauma on depression in this sample appear to be established earlier in childhood (ages 10-14 or younger) and persist in a relatively stable manner into middle adolescence when the risk for drug use may be heightened.