A new study has found that people taking antidepressants are more likely to gain weight over time, with continuous use doubling the risk of developing obesity.

The research, led by the Hospital del Mar Research Institute and published in Frontiers in Psychiatry, analyzed data from over 3,000 adults and found an average 2% increase in body weight among those using antidepressants.

Tracking Weight Changes Over Six Years

The study followed 3,127 adults for six years, with an average participant age of 55. Of these, 16.4% reported using antidepressants at some point during the study:

• 5.1% took antidepressants continuously
• 6.2% started taking them during the study
• 5.1% took them at the beginning but later stopped

While all participants experienced some weight gain (about 0.5 kg on average), those taking antidepressants gained more weight than those who never used them. The greatest weight gain was observed in those who took antidepressants throughout the entire study period.

Dr. Camille Lassale, a researcher at Hospital del Mar and ISGlobal, explained:

“All individuals taking antidepressants had a higher likelihood of gaining weight and developing obesity. This risk is even greater for those who use these medications continuously.”

The Impact of Antidepressants on Weight

The study accounted for various factors such as age, sex, socioeconomic status, lifestyle habits, and the presence of depression, yet the link between antidepressant use and weight gain remained strong. Key findings include:

• People who discontinued antidepressants still gained 1.8% more weight than those who never used them.
• People who started antidepressants or used them continuously gained an additional 2% of body weight over the study period.
• Those who used antidepressants long-term had double the risk of developing obesity compared to non-users.

The research also found that women, older adults, and individuals with less healthy lifestyles were more likely to experience weight gain while on antidepressants.

Why This Matters for Patients and Doctors

Dr. Gabriela Lugon, a researcher at Hospital del Mar, emphasized that while antidepressants are essential for managing mental health conditions, their impact on weight should not be overlooked.

“We cannot simply prescribe antidepressants for their positive effects without also considering this side effect,” she said.

The study’s authors recommend closely monitoring weight changes in individuals taking antidepressants, as well as checking other cardiometabolic health markers.

Dr. Víctor Pérez, head of Psychiatry at Hospital del Mar, highlighted that while not all antidepressants cause weight gain, some medications—such as mirtazapine and paroxetine—are particularly associated with significant increases in body weight.

“Due to the risk of patients discontinuing treatment because of weight gain, we must consider alternative therapeutic strategies to complement pharmacological treatment,” he warned.

The Bigger Picture: Depression, Obesity, and Antidepressant Use

Depression affects 280 million people worldwide, with women being twice as likely as men to experience the condition. At the same time, obesity impacts 650 million people globally, creating a bidirectional relationship between these two health issues.

Weight gain is one of the main reasons people stop taking antidepressants, which can be a major concern for mental health treatment.

With Spain ranking among the highest in antidepressant use in Europe, alongside Sweden and Portugal, these findings highlight the need for better management strategies to balance the benefits of antidepressants with their potential side effects.

This is the first study of its kind in Spain and involved researchers from multiple institutions, including CIBEROBN, CIBERCV, University College London, and the Girona Biomedical Research Institute. Future research will aim to further explore how different antidepressants affect weight and identify strategies to help patients manage their health while receiving treatment.

The research findings can be found in Frontiers in Psychiatry.

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