Are expectancies and peers involved in the relation between depressive mood, anxiety and cannabis use in adolescence?

Background: Cannabis is the most commonly used illicit drug among teenagers and depression is one of the most common psychopathologies in adolescence. The specific symptom of depressive mood is present in 30% to 40% of adolescents in regular school settings. Links between cannabis use and depression have been highlighted, especially in adolescence. But questions remain about the strength of the association between lifetime cannabis use, depressive mood and anxiety, and about the mechanism underpinning the link. Aim: The aim of this study was to clarify the relationship between depressive mood and lifetime cannabis use in adolescents, particularly through the mediating role of anxiety and cannabis use effect expectancies, and the moderating role of peer cannabis use. Methods: A questionnaire was administered to 1,246 Belgian teenagers aged 16–17 years. ANOVA, chi-square, logistic regressions and mediation/moderation analyses were carried out to model lifetime cannabis use. Results: Depressive mood was positively correlated with lifetime cannabis use. Social anxiety, trait-anxiety and cognitive impairment effect expectancies mediated the effect of depression on lifetime cannabis use. The direct effect of depression on lifetime cannabis use increased when mediators were introduced into the relation, revealing their suppressive effects. The number of peer cannabis users moderated this model. Conclusion: Findings are discussed in terms of potential risk factors (depressive mood) or protective factors (anxiety and expectancies) for lifetime cannabis use, including the self-medication hypothesis.