The development of body mass index (BMI) in depressed patients during an antidepressant treatment and its effects on depressive symptomatology

Introduction Both depressed patients and also high-risk populations for developing depression have a high prevalence of obesity. A recent meta-analysis suggests that there may be an overlap in pathophysiology of both diseases. The aim of our study was to investigate the relationship between BMI and depressive symptomatology at baseline and during the course of an antidepressant treatment. Additionally we wanted to examine BMI as a potential predictor of antidepressant treatment response.

Methods 889 MDD patients were treated by a pre-defined antidepressant treatment algorithm within the Early Medication Change (EMC) study. Patients were divided in three BMI groups according to WHO criteria: low/normal weight (BMI < 25), overweight (BMI 25-<30) and obese (≥ 30). Depression severity (HAMD17) and BMI were assessed weekly from baseline to week 8. In linear regression models, BMI at baseline and the course of BMI during treatment were investigated as possible predictors of antidepressant response. Co-variables like age, sex, comorbidities and plasma levels of antidepressant drugs were investigated.

Results 388 (48%) patients showed low or normal weight, 251 (31%) were overweight and 172 (21%) were obese. Patients with BMI between 25 – 30 showed a better response to antidepressant treatment than obese or normal weight patients. Also a weight gain during the course of treatment was associated with a better improvement of depressive symptomatology. BMI at baseline was correlated to an improvement in specific symptoms (neurovegetative and cognitive). Other co-variables were not able to explain the different response rates of the BMI subgroups.

Conclusion To our knowledge, this is the first study investigating the association between the course of BMI and the antidepressant treatment response during an antidepressant treatment. We could show that a decrease of depression severity is correlated to an increase of BMI. The underlying mechanisms remain unclear and require further investigations.