The Potential Influence of Group Membership on Outcomes in Indicated Cognitive-Behavioral Adolescent Depression Prevention

Background: Adolescent depression prevention programs are typically delivered in groups in which adolescents share a common setting and interventionist, but the influence of the group is usually ignored or statistically controlled. We tested whether the primary outcomes of reductions in depressive symptoms and future onset of major depressive disorder (MDD) varied as a function of group membership. Methods: Data were available from two randomized trials in which 220 adolescents received the Blues Program indicated prevention intervention in 36 separate groups; participants were assessed at baseline, post intervention, and at 6-, 12-, and 24-month follow-ups. Results: Ten percent of participants had developed MDD 2 years post intervention. Group-level effects for MDD onset over follow-up were nonsignificant (accounted for <1% of variance; ICC = 0.004, ns). Group-level effects for depressive symptom change across the follow-up period were also nonsignificant (ICC = 0.001, ns) but group effects accounted for 16% of depressive symptom change immediately post intervention (ICC = 0.159, p < 0.05). Group-level clustering of posttest depressive symptoms was not associated with size of group or gender composition. Conclusions: Membership in specific adolescent cognitive-behavioral depression prevention groups may have an impact in terms of immediate symptom reduction but does not appear to have significant prevention effects in terms of long-term symptom change or MDD onset.