Adolescent smoking and depression: evidence for self-medication and peer smoking mediation.

AIMS: The nature of the relationship between adolescent smoking and depression is unclear and the mechanisms that account for the comorbidity have received little investigation. The present study sought to clarify the temporal precedence for smoking and depression and to determine whether these variables are linked indirectly through peer smoking. PARTICIPANTS: The sample was composed of 1093 adolescents participating in a longitudinal study of the behavioral predictors of smoking adoption. DESIGN AND MEASUREMENTS: In this prospective cohort study, smoking, depression, peer smoking and other covariates were measured annually from mid-adolescence (9th grade; age 14) to late adolescence (12th grade, age 18).
FINDINGS: Parallel processes latent growth curve models supported a bidirectional relationship between adolescent smoking and depression, where higher depression symptoms in mid-adolescence (age 14) predicted adolescent smoking progression from mid- to late adolescence (ages 14-18). A significant indirect effect indicated that higher depression symptoms across time predicted an increase in the number of smoking peers, which in turn predicted smoking progression from mid-adolescence to late adolescence. In addition, smoking progression predicted a deceleration of depression symptoms from mid- to late adolescence. A significant indirect effect indicated that greater smoking at baseline predicted a deceleration in the number of smoking peers across time, which predicted a deceleration in depression symptoms from mid-adolescence to late adolescence.
CONCLUSIONS: The current study provides the first evidence of bidirectional self-medication processes in the relationship between adolescent smoking and depression and highlights peer smoking as one explanation for the comorbidity.