Does Body Mass Index Affect Depression Treatment Outcomes?

September 24, 2026

Depression and body weight are often linked, but researchers are still trying to understand how the two are connected. Since antidepressant treatment does not work the same way for everyone with Major Depressive Disorder (MDD), researchers have been exploring whether body weight may influence how well someone responds to treatment. A recent CAN-BIND study examined whether body mass index and being overweight were associated with antidepressant treatment outcomes in individuals with MDD.

**What is Body Mass Index (BMI)?**

Body Mass Index (BMI) is a measurement that uses a person’s height and weight to estimate their body size. It is commonly used in research to group individuals as underweight, normal weight, overweight, or obese.

Depression and body weight can influence each other. Obesity is common among individuals living with depression and can affect overall quality of life. Previous research has found that obesity may increase the risk of developing depression, while depression may also increase the risk of developing obesity. Other studies have suggested that body weight may be related to depression severity and response to treatment.

However, findings have been inconsistent. Some studies have found that individuals with higher body weight may respond differently to certain antidepressant treatments, while others have found no clear relationship. This raises the question of whether BMI can predict how someone will respond to antidepressant medication.

How the Study Worked

Participants received antidepressant treatment (escitalopram) for 8 weeks. Those who responded to treatment continued with the same medication for another 8 weeks, while those who did not respond received an additional medication (aripiprazole) alongside the antidepressant. Researchers measured participants’ body mass index (BMI) at the start of the study and examined whether BMI or being overweight was associated with changes in depression symptoms, treatment response, or remission. They also looked at physical activity and behavioural patterns to understand whether these factors were related to BMI or treatment outcomes.

What Did This Study Reveal?

BMI was not linked to antidepressant treatment outcomes. Individuals with different BMI levels were just as likely to respond to treatment or reach remission, and changes in depression symptoms did not differ based on BMI.
Physical activity and most behaviour measures were not related to how individuals responded to treatment. A measure of behavioural inhibition was associated with remission after 8 weeks, but this was not seen after 16 weeks.
BMI was not linked to depression severity or the other factors studied. BMI, physical activity, and being overweight were not found to be related to depression severity or the behaviour measures at the start of treatment.

Why This Matters

While some previous studies have found that BMI or being overweight may be linked to how individuals respond to treatment, this study did not find the same relationship. These findings suggest that more research is needed to understand if and how body weight may relate to depression treatment outcomes. Other factors related to physical and mental health may also play a role in treatment outcomes. Studying these factors together could help explain why treatment works well for some individuals but not for others.

“…the effect of body weight on treatment outcomes is complex and may vary depending on the measure used (i.e., BMI, body weight, BMI categories) and the antidepressants examined.”

Limitations to Consider

While this study provides insight into the relationship between body weight and antidepressant treatment outcomes, some limitations should be considered. First, the relatively small number of participants in the study limited the researchers’ ability to look closely at different BMI groups. For example, the researchers did not examine individuals who were underweight or distinguish between those who were overweight and those with obesity. In addition, because participants were part of a clinical trial, the findings of the study may not fully reflect outcomes for individuals receiving depression treatment in regular clinical settings. Finally, BMI is only one measure of physical health, and this study did not examine other factors (ex. psychological, behavioural, biological, and metabolic) that could influence how body weight and depression affect each other. Future studies that explore these factors may help provide a better understanding of why and how body weight and depression can affect individuals differently.

Final Takeaway

This study found that BMI and being overweight did not predict how well participants responded to antidepressant treatment. These findings highlight the complexity and the inconsistency in the relationship between body weight and depression treatment shown in previous studies. Future research examining a wider range of BMI groups and potential moderators may help explain why some studies find a relationship between body weight and antidepressant treatment while others do not.

“…our findings suggest that neither BMI nor being overweight influence treatment outcomes in patients with MDD who are treated with escitalopram with and without adjunctive aripiprazole in this study. Larger studies with more diverse samples are needed to validate these findings.”

Citation: Kim, H. K., Jones, B. D. M., Hahn, M. K., Agarwal, S. M., Farzan, F., Frey, B. N., Kennedy, S. H., Foster, J. A., Lam, R. W., Milev, R., Müller, D. J., Parikh, S. V., Soares, C. N., Taylor, V. H., Turecki, G., Uher, R., & Kloiber, S. (2026). The association between body mass index and treatment outcomes in major depressive disorder: A CAN-BIND-1 study. Journal of Psychiatric Research, 198, 252–256. https://doi.org/10.1016/j.jpsychires.2026.03.036