Antidepressant-induced weight gain is a significant concern for many patients. In 2023, about 16% of Canadians were prescribed antidepressants, making them one of the most widely used medication classes. These drugs are commonly prescribed for depression, anxiety, chronic pain, and post-traumatic stress disorder (PTSD).
While antidepressants are effective, weight gain is a well-documented side effect. This can lead to poor adherence, reduced treatment success, and potential long-term metabolic health risks such as diabetes or cardiovascular disease.
Which Antidepressants Are Linked to Weight Gain?
A large observational cohort study (2010–2019) examined 183,118 patients aged 20–80 years who were new users of first-line antidepressants:
- Sertraline (reference drug) – 20% of patients
- Citalopram – 16%
- Bupropion – 15%
- Paroxetine – 4% (least common)
- Escitalopram, Fluoxetine, Duloxetine, Venlafaxine – remaining patients
Key Findings on Weight Change (6 months):
- Escitalopram: +0.41 kg
- Paroxetine: +0.37 kg
- Duloxetine: +0.34 kg
- Venlafaxine: +0.17 kg
- Citalopram: +0.12 kg
- Fluoxetine: Similar to sertraline
- Bupropion: –0.22 kg (weight loss)
Patients on escitalopram, paroxetine, and duloxetine were 10–15% more likely to gain ≥5% of baseline body weight. In contrast, bupropion users were 15% less likely to experience weight gain.
Antidepressants and Adherence
Medication adherence is often affected by side effects. The study found:
- Bupropion had the highest adherence at 6 months (41%).
- Other antidepressants ranged between 28–36% adherence.
This suggests that weight gain may play a role in treatment discontinuation, making antidepressant choice an important factor in long-term success.
Implications for Pharmacists
Pharmacists play a critical role in helping patients navigate antidepressant therapy and weight concerns.
- Counsel patients on the potential for weight changes with different antidepressants.
- Screen for weight and metabolic risks before initiating therapy.
- Highlight bupropion as an option for patients with weight management concerns.
- Monitor adherence and address side effects promptly to prevent treatment drop-out.
Conclusion
Antidepressant-induced weight gain is an important clinical issue that can impact both adherence and long-term health. While medications like escitalopram, paroxetine, and duloxetine are associated with higher weight gain, bupropion offers a weight-neutral or weight-losing alternative.
For patients with metabolic health concerns, careful selection of antidepressants — combined with ongoing pharmacist support — can improve both treatment outcomes and quality of life.
References
- Petimar J, Young JG, Yu H, et al. Medication-induced weight change across common antidepressant treatments: a target trial emulation study. Ann Intern Med 2024;177:993-1003.
- IQVIA. Trends in the use of antidepressants in Canada, 2019–2023. November 25, 2024. (accessed January 28, 2025).
Disclaimer
This blog is for educational purposes only and does not replace medical advice. Patients should consult their healthcare provider before making any changes to antidepressant therapy.