A new study from Spain has found a connection between the use of antidepressant medications and weight gain. Researchers tracking individuals over several years discovered that those taking antidepressants experienced, on average, a two percent increase in their body weight. This finding, published in Frontiers in Psychiatry, highlights the importance of considering weight management as part of depression treatment and monitoring.
Experts have long known that depression is a widespread mental health issue, affecting millions of people around the globe. It is estimated that hundreds of millions of individuals struggle with depression, a condition that can significantly impact daily life and overall well-being. For many, antidepressant medications are a primary form of treatment, often used in combination with therapy. In fact, antidepressants are among the most frequently prescribed medications worldwide, with usage rates increasing over the past few decades. In Spain, like in other developed nations, a significant portion of the adult population uses these medications to manage their depressive symptoms.
While antidepressants can be effective in alleviating the symptoms of depression, they are not without potential side effects. These medications can cause a range of unwanted effects, from sleep disturbances and dizziness to digestive problems and changes in weight. Weight gain, in particular, is a notable concern, as it can lead individuals to stop taking their medication, even if it is helping their depression. This is especially concerning because obesity, a condition affecting a large portion of the global population, carries its own serious health risks.
Interestingly, there’s a complex relationship between obesity and depression. Research suggests that obesity can increase the risk of developing depression, and conversely, depression can increase the risk of becoming obese. Scientists believe shared biological factors might contribute to this link.
One potential factor linking depression and obesity is the use of antidepressants themselves. While some antidepressants are more likely to cause weight gain than others, and some may even lead to weight loss, much of the existing research on this side effect has focused on short-term medication use, typically over weeks or months. There has been a lack of research examining the long-term effects of antidepressant use on weight over many years in real-world settings.
Some prior studies in other countries have started to explore this gap, suggesting that longer-term antidepressant use is associated with increased weight gain. However, these studies often looked at overall antidepressant use without considering different patterns of use over time, such as starting and stopping medication. Therefore, this new study aimed to investigate how different patterns of antidepressant use over a six-year period relate to changes in weight and the risk of becoming obese in a group of Spanish adults.
To conduct their investigation, the research team used data from an ongoing study in Spain called the Girona Heart Registry study, which is tracking the health of people in the Girona province to understand heart disease risk factors. For this specific analysis, the researchers focused on over 3,000 adults who participated in the study’s third phase starting in 2005. These individuals were followed up approximately six years later.
At the beginning of the study and at the follow-up visit, trained nurses measured the participants’ height and weight using standardized procedures. This allowed the researchers to calculate each person’s body mass index, a measure of body fat based on height and weight, and to determine who was considered obese, defined as having a body mass index of 30 or higher.
At both the initial visit and the follow-up visit, participants were asked about their medication use. Specifically, they were asked to list all medications they were taking. Researchers then categorized these medications, identifying those classified as antidepressants, including selective serotonin reuptake inhibitors and other types.
By looking at medication use at both time points, the researchers were able to categorize participants into four groups based on their antidepressant use over the six-year period: those who never used antidepressants, those who used antidepressants at the start but stopped by the follow-up, those who started using antidepressants after the initial visit and were using them at follow-up, and those who used antidepressants at both the initial and follow-up visits.
In addition to medication and weight measurements, the researchers collected information on other factors that could influence weight and health. This included demographic information like age and sex, as well as lifestyle factors such as education level, marital status, smoking habits, diet quality measured using a Mediterranean diet score, and physical activity levels. They also collected data on pre-existing conditions like diabetes and high blood pressure, as well as the use of antipsychotic medications, as these could also affect weight.
The researchers also assessed depressive symptoms at the follow-up visit using a standard questionnaire. They also linked participant data to electronic health records to identify any diagnoses of depression made by doctors during the follow-up period. This allowed them to account for depression itself as a factor that might influence weight changes, separate from the effects of antidepressants.
After analyzing the data, the researchers found that all patterns of antidepressant use were associated with greater weight gain compared to those who never used these medications. Specifically, individuals who started antidepressants during the study period, those who continued using them throughout, and even those who started and then stopped, all experienced a greater percentage increase in their body weight over the six years compared to those who never used antidepressants.
“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,” explained Camille Lassale, a researcher at the Hospital del Mar Research Institute and the Barcelona Institute for Global Health (ISGlobal).
On average, this weight gain amounted to approximately a two percent increase in body weight beyond what was seen in non-users, even after accounting for factors like age, sex, lifestyle, pre-existing conditions, and depressive symptoms. Interestingly, the association between antidepressants and weight gain appeared to be more pronounced in certain subgroups of people, specifically women, individuals younger than 55 years old, and those who were at a healthy weight at the beginning of the study. Among participants who were not obese at the start, those who were using antidepressants repeatedly over the six years had a higher risk of becoming obese by the follow-up.
Gabriela Lugon, a researcher at Hospital del Mar and a resident physician in the Preventive Medicine and Public Health Teaching Unit at Hospital del Mar, Pompeu Fabra University, and the Barcelona Public Health Agency, said that the findings highlight the importance of considering the link between antidepressants and weight gain when prescribing these medications and the need for regular weight monitoring.
“We cannot simply prescribe antidepressants for their positive effects without also considering this side effect,” Lugon said. For this reason, the study’s authors emphasize the need to monitor weight changes in individuals receiving antidepressant treatment, along with other indicators of cardiometabolic health.
Víctor Pérez, head of the Psychiatry Department at Hospital del Mar, emphasized that antidepressants are highly effective for treating some of the most common mental illnesses. However, “their effect on weight is not universal, although certain medications, such as mirtazapine and paroxetine, can cause significant weight gain.” He also warned that “due to the risk of patients discontinuing treatment because of weight gain, we must consider alternative therapeutic strategies to complement pharmacological treatment.”
The researchers acknowledged some limitations to their study. Medication use was based on self-report at only two time points, which might not perfectly capture medication use over the entire six-year period. Additionally, the study looked at antidepressant use in general, rather than examining the effects of specific types of antidepressants, which could have different impacts on weight. The study was also observational, meaning it cannot definitively prove that antidepressants directly cause weight gain, only that there is an association. Other unmeasured factors could potentially be influencing the results.
For future research, the scientists suggested that studies should investigate the effects of specific antidepressant medications on weight, as different drugs may have varying effects. They also recommended combining data from long-term studies like theirs with electronic health records to gather even larger amounts of data and follow people for longer periods. Future studies should also consider the use of other psychiatric medications besides antidepressants and focus on understanding the effects in younger populations, given the early onset of depression for many.
The study, “Trajectories of antidepressant use and 6-year change in body weight: a prospective population-based cohort study,” was Camille Lassale, Gabriela Lugon, Álvaro Hernáez, Philipp Frank, Jaume Marrugat, Rafael Ramos, Josep Garre-Olmo, and Roberto Elosua.
