Cognitive behavioral program for the prevention of depression in at-risk adolescents: isolating the effects of dose.

The current study estimated effects of intervention dose (attendance) of a cognitive behavioral prevention (CBP) program on depression-free days (DFDs) in adolescent offspring of parents with a history of depression. As part of secondary analyses of a multisite randomized controlled trial, we analyzed the complete intention-to-treat sample of 316 at-risk adolescents ages 13 to 17 years. Youth were randomly assigned to the CBP program plus usual care (n = 159) or to usual care alone (n = 157). The CBP program involved 8 weekly acute sessions and 6 monthly continuation sessions. Results showed that higher CBP program dose predicted more DFDs, with a key threshold of approximately 75% of a full dose in analyses employing instrumental variable methodology to control multiple channels of bias. Specifically, attending at more than 75% of acute phase sessions led to 45.3 more DFDs over the 9-month period after randomization, which accounted for over 12% of the total follow-up days. Instrument sets were informed by study variables and external data, including weather and travel burden. In contrast, conventional analysis methods failed to find a significant dose-outcome relation. Application of the instrumental variable approach, which better controls the influence of confounding, demonstrated that higher CBP program dose resulted in more DFDs. This article is part of a Special Collection on Mental Health.