Supplementary Material for: Substance use -related factors and recurrent depression among former adolescent psychiatric inpatients.

Introduction: Recurrent depression is a challenging and common disorder in clinical psychiatry. Comorbid substance use disorder poses a challenge to effective treatments. The association between depression and substance abuse is widely documented, but less is known about how the recurrence of depression is associated with substance use disorders and the temporal connections between the two disorders in adolescence and early adulthood.
Methods: In this study we analyzed the associations between recurrent depression and substance use patterns in former adolescent psychiatric inpatients, during initial inpatient hospitalization and follow-up period of 10-15 years. Study population consisted of 235 individuals admitted for adolescent psychiatric inpatient care, of whom 84 were in recurrent depression group and 151 in single depressive episode group. Substance use experimentation ages, substance use frequencies during adolescence, onset ages of substance use disorders and number of substance use disorder diagnoses in adolescence and early adulthood were analysed between the the two groups.
Results: Recurrent depression was associated with alcohol use disorders (p=0.014) and multiple drug use disorders (p=0.034) in early adulthood in males. In logistic regression analysis, alcohol use disorder was found to associate with recurrent depression in males (OR 3.6, 95% CI 1.27-10.75, p=0.017). There was no statistically significant difference in temporal associations between recurrent or single episode depression in regard to onset age of substance use.
Conclusions: Our results emphasize the need for early recognition and integrated treatment of substance use and depression in adolescence.