Escalation to Major Depressive Disorder among adolescents with subthreshold depressive symptoms: Evidence of distinct subgroups at risk

Background The presence of subthreshold depressive symptoms (SubD) in adolescence is associated with high prospective risk of developing Major Depressive Disorder (MDD). Little is known about variables that predict escalation from SubD to MDD. This study used a longitudinal prospective design in a community sample of adolescents to identify combinations of risk factors that predicted escalation from SubD to MDD. Methods Classification tree analysis was used to identify combinations of risk factors that improved the sensitivity and specificity of prediction of MDD onset among 424 adolescents with a lifetime history of SubD. Results Of the 424, 144 developed MDD during the follow-up period. Evidence for multiple subgroups was found: among adolescents with poor friend support, the highest risk of escalation was among participants with lifetime histories of an anxiety or substance use disorder. Among adolescents with high friend support, those reporting multiple major life events in the past year or with a history of an anxiety disorder were at highest risk of escalation. Limitations Study findings may not inform prevention efforts for individuals who first develop SubD during adulthood. This study did not examine the temporal ordering of predictors involved in escalation from SubD to MDD. Conclusions Adolescents with a history of SubD were at highest risk of escalation to MDD in the presence of poor friend support and an anxiety or substance use disorder, or in the presence of better friend support, multiple major life events, and an anxiety disorder. Findings may inform case identification approaches for adolescent depression prevention programs.