The prescription of antidepressants continues to increase year after year, and nearly 10% of Spaniards are taking them. This study attempts to establish the differences in which antidepressants cause the greatest weight gain, but it reminds us that all of them do. That a medication causes weight gain is a crucial issue because weight gain deteriorates physical health and quality of life, can lead to treatment abandonment, and also decrease self-esteem, which is particularly important when we are talking about mental health. 

The importance of this research, beyond contributing to choosing the right antidepressant for those who need it, is that we can reconsider the harm caused by their prescription and limit it to those who will truly benefit from this treatment. Many common mental sufferings can be resolved with social and/or psychological interventions, without the need for antidepressants, although this is the most frequent and immediate response. Lastly, this study highlights the need to properly warn people who are going to take antidepressants about the adverse effects, such as weight gain in this case, and to reflect on the possibility of prescribing them through an informed consent document, as is usually done with surgical interventions and other treatments. 

This finding is in line with previous work from our [research] group published in 2019 in which we performed a systematic review aimed to evaluate the potential association of antidepressant and antipsychotic therapy with body weight gain in cohort studies. We included 27 independent eligible cohort studies with children (2-18 years old) and adult (18-103 years old) subjects. Most of the studies included showed a 5% weight gain in individuals using antidepressant therapy. However, Quetiapine, Haloperidol, Trifluoperazine, Risperidone, Aripiprazole, Olanzapine, and Clozapine increased body weight ≥7% from baseline, which is considered a clinically significant result. Interestingly, weight loss was found in individuals treated with Bupropion.

The study design - emulated clinical trial - is an innovative way to infer causality based on real life data coming from electronic health records. This study stands out for its methodological rigour and large sample size. The limitations are the relatively short-term of weight change over 2 years (another study using electronic health records in the UK looked at weight change over 10 years), and the absence of data on lifestyle factors known to affect weight gain such as diet, alcohol use and physical activity.  

The results are in line with the literature regarding bupropion, and can help patients and doctors making decisions regarding the type of antidepressant to prescribe.