The bidirectional relationship between body mass index and treatment outcome in adolescents with treatment-resistant depression.

Objective: Depression and obesity are associated, but the impact of obesity on depression treatment outcome, or, conversely, the impact of treatment on body mass index (BMI) in depressed adolescents has not been reported. In this article, we examine the bidirectional relationships between BMI and treatment response in adolescents with treatment-resistant depression. Method: Participants in the Treatment of Selective Serotonin Reuptake Inhibitor (SSRI) Resistant Depression in Adolescents (TORDIA) study had height and weight assessed at baseline, weekly for the first 6 weeks, biweekly for the next 6 weeks, and monthly from weeks 12 through 24. The impact of baseline BMI as a predictor and moderator of treatment response was assessed. In addition, participants' changes in BMI were assessed as a function of specific treatment assignment and treatment response. Results: Participants assigned to SSRIs had a greater increase in BMI-for-age-sex z-score and weight than did those assigned to venlafaxine. Post-hoc, those treated with paroxetine or citalopram had the biggest increases in BMI, relative to fluoxetine or venlafaxine. Overweight or obesity was neither a predictor nor a moderator of treatment outcome, nor of subsequent BMI change. Conclusions: Overweight status does not appear to affect treatment response in adolescents with resistant depression. The successful treatment of depression does not appear to favorably affect weight or BMI. Fluoxetine and venlafaxine are less likely to cause an increase in BMI than paroxetine or citalopram.