Body mass index and atypical balance as predictors of winter depression remission in cognitive-behavioral therapy and light therapy.

BACKGROUND

Efficacious treatments for winter seasonal affective disorder (SAD) include light therapy (LT) and cognitive-behavioral therapy (CBT-SAD); however, baseline characteristics may differentially predict treatment outcomes. This study investigated body mass index (BMI) and atypical balance (the proportion of atypical depression symptoms), as predictors of depression remission.

METHODS

The parent study randomized 177 adults diagnosed with Major Depression, Recurrent with Seasonal Pattern to 6-weeks of CBT-SAD (n = 88) or LT (n = 89) and followed participants one and two winters later. At baseline, BMI was measured and atypical balance was derived using the Structured Interview Guide for the Hamilton Rating Scale for Depression-Seasonal Affective Disorder Version (SIGH-SAD) as 8-item atypical subscale score/total SIGH-SAD score × 100. Depression remission was defined using standard SIGH-SAD cutpoints. Hierarchical logistic regressions tested the main effects of treatment modality, BMI, and atypical balance and their interactive effects on depression remission at post-treatment and follow-ups.

RESULTS

The BMI × treatment and atypical balance × treatment interactions significantly predicted depression remission at second winter follow-up. The probability of remission was higher in CBT-SAD than LT at BMI ≤ 26.1 and atypical balance ≤ 40.3%. This predictive relationship survived when adjusting atypical balance for BMI, but not vice-versa.

LIMITATIONS

Participants were predominantly White and older. BMI does not account for muscle mass or fat distribution.

CONCLUSIONS

BMI and atypical balance prescriptively predicted higher likelihood of depression remission two winters following CBT-SAD but not LT. This work informs clinical decision-making and precision medicine efforts.