In accordance with previous studies, a high body mass index (BMI) at the onset of treatment for major depressive disorder (MDD) has been found to be correlated with poor treatment outcome. However, an initial increase in BMI during said treatment is associated with increased reduction of depression severity, according to an article published in the Journal of Affective Disorders.

The researchers sought to investigate the relationship between BMI and MDD, both in symptomatology and antidepressant response. The study performed a secondary exploratory analysis of 811 participants from an early medication change trial in which their BMI and severity of depressive symptoms were assessed every week for about 8 weeks. The BMI subgroups were created according the World Health Organization criteria of normal or low weight (BMI<25; n=388; 48%), overweight (BMI of 25-30; n=251; 31%), or obese (BMI>30; n=172; 21%). Depressive symptoms were assessed using the Hamilton Depression Rating Scale and inventory of depressive symptomatology. The researchers also looked at the relationship between change in BMI and depressive symptom complex, such as mood and neurovegetative symptomatology. Additionally, axis 1 and 2 and physical comorbidities were assessed between the subgroups measured by the cumulative illness rating scale.

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Researchers found many significant differences in the clinical variables and severity of depression between the BMI subgroups through their exploratory statistical analysis. Patients of normal weight had higher depression rating scale sum scores at baseline (P <.001), than those with higher BMIs and their BMI significantly increased (P <.001) throughout the duration of treatment. Additionally, participants classified as obese had higher cumulative illness rating scale sum scores (P <.001), more previous depressive episodes (P =.006) and a significantly decreased BMI during treatment (P =.001). Furthermore, patients with a larger increase of BMI during the duration of treatment experienced a distinct decrease in depression severity, and a significant decrease was seen in patients with a BMI<25 (P =.001) and those with a BMI between 25 and 29.9 (P =.028). Lastly, there were differences in the BMI subgroups for depressive symptom complexes, such as in neurovegetative symptoms (P =.008) and cognitive symptoms (P =.014).

Some limitations for this study are listed, the first being that it is a secondary exploratory analysis of a subset of participants from an early medication change trial. The use of BMI as a moderator for treatment response as it is not as specific as it could ideally be to establish a relationship between treatment response and metabolic dysfunction. Additionally, researchers were not able to access BMI data from before the trial assessed or the activity level of the participants.

Researchers of this study confirmed that “depression severity and antidepressant treatment response depends on BMI as patients with lower BMI showed higher response rates.” Additionally, they concluded that an increase of the patients’ initial BMI at the onset of treatment is a predictor of larger decrease of depressive symptomatology during treatment. However, “the mechanisms underlying the relationship between BMI and depression and anti-depressant treatment response, respectively, are so far unknown and require further investigation.”

One author declared affiliations with the pharmaceutical industry. Please see original reference for a full list of authors’ disclosures.

Reference
Dreimüller N, Lieb K, Tadić A, Engelmann J, Wollschläger D, Wagner S. Body mass index (BMI) in major depressive disorder and its effects on depressive symptomatology and antidepressant response
[published online July 2, 2019]. J Affect Disord. doi: 10.1016/j.jad.2019.06.067