The role of comorbid anxiety in exercise and depression trials: Secondary analysis of the SMILE‐II randomized clinical trial

OBJECTIVES: To explore the anxiolytic effects of a 4-month randomized, placebo-controlled trial of exercise and antidepressant medication in patients with major depressive disorder (MDD), and to examine the potential modifying effects of anxiety in treating depressive symptoms. MATERIALS AND METHODS: In this secondary analysis of the SMILE-II trial, 148 sedentary adults with MDD were randomized to: (a) supervised exercise, (b) home-based exercise, (c) sertraline, or (d) placebo control. Symptoms of state anxiety measured by the Spielberger Anxiety Inventory were examined before and after 4 months of treatment. Depressive symptoms were assessed by the Hamilton Depression Rating Scale (HAMD) and Beck Depression Inventory-II (BDI-II). Analyses were carried out using general linear models. RESULTS: Compared to placebo controls, the exercise and sertraline groups had lower state anxiety scores (standardized difference = 0.3 95% CI = -0.6, -0.04; p = 0.02) after treatment. Higher pretreatment state anxiety was associated with poorer depression outcomes in the active treatments compared to placebo controls for both the HAMD (p = .004) and BDI-II (p = .02). CONCLUSION: Aerobic exercise as well as sertraline reduced symptoms of state anxiety in patients with MDD. Higher levels of pretreatment anxiety attenuated the effects of the interventions on depressive symptoms, however, especially among exercisers. Patients with MDD with higher comorbid state anxiety appear to be less likely to benefit from exercise interventions in reducing depression and thus may require supplemental treatment with special attention to anxiety.