Body mass index (BMI) in major depressive disorder and its effects on depressive symptomatology and antidepressant response

Background: Obesity is one of the most prevalent somatic comorbidities of Major Depressive Disorder (MDD). We aimed to investigate the relationship between body mass index (BMI) and MDD, the symptomatology of the disorder as well as the outcome of antidepressant treatment.

Methods: Early medication change (EMC) trial participants with BMI measurement (n = 811) were categorized according to WHO-criteria in normal or low weight (BMI < 25), overweight (25-< 30), and obese (≥30). Depression severity and BMI was assessed in weekly intervals up to 8 weeks. BMI at baseline and course of BMI during the study were investigated in linear regression models as possible moderators of therapy response. Possible moderators such as plasma concentrations of applied drugs, sex, comorbidities or age were controlled.

Results: 388 (48%) patients showed normal weight, 251 (31%) were overweight and 172 (21%) obese. Linear regression analyses revealed an association between BMI and antidepressant therapy outcome: Overweight patients showed the best response to antidepressant treatment. BMI at baseline was significantly correlated with improvement in neurovegetative and cognitive symptoms of depression. Furthermore, weight gain during the study was associated with better therapy response, independent of symptom complex. Other moderators including serum concentrations of drugs were not able to explain the differences between the BMI groups.

Limitations: Secondary exploratory analysis. No investigation of visceral fat.

Conclusion: We showed for the first time that patients with higher initial increase in BMI showed larger decrease in depression severity during study. The underlying mechanisms are unclear and require further investigation.