Antidepressants and weight gain

On 23rd May 2018, an article was published in the BMJ entitled “Antidepressant utilisation and incidence of weight gain during 10 years’ follow-up: population based cohort study” (Ref 1). It made headlines across the pond from the UK Independent newspaper (Ref 2) to Time Magazine (Ref 3). The journal and media articles should not have been a surprise, as it has long been known that certain medications impact weight, especially drugs for mind health. This study quantified the gain and noted differences between medications and thus will be useful to patients and doctors alike.

The study

The study objective was simple: “To evaluate the long term association between antidepressant prescribing and body weight.” The data used came from the UK Clinical Practice Research Datalink (CPRD). This is one of the world’s largest databases of primary care electronic health records. Approximately 7% of UK general practices participate by sharing anonymised information. Data collection has been ongoing since 1990.

For this BMJ study, a sample of 136,762 men and 157,957 women was taken from the population of 2,006,296 patients registered on the CPRD between November 2004 and October 2014. Participants were aged 20 or older and had at least three BMI measurements recorded. BMI was the main outcome of interest and the following BMI categories were used: 18.5-24.9 (normal weight); 25.0-29.9 (overweight); 30.0-34.9 (obese); 35.0-35.9 (severe obesity); 40.0-44.9 (morbid obesity), and ≥45.0 (super obesity).

The particular measures of interest to the researchers were i) the incidence of an increase in body weight of 5% or more and ii) the transition from one BMI group to the one above (normal to overweight, or overweight to obese, for example). The researchers adjusted for a number of other factors that could impact weight over time – such as age, sex, diabetes, co-prescribing of other drugs that could impact weight, as examples. Efforts were thus taken to try to isolate the impact of antidepressants on weight.

Antidepressants were grouped into types: tricyclic and related antidepressants (TCAs); monoamine oxidase inhibitors (MAOIs); selective serotonin reuptake inhibitors (SSRIs); serotoninnoradrenaline (norepinephrine) reuptake inhibitors (SNRIs); and other antidepressant drugs. Individual antidepressant drugs were also reviewed: mirtazapine; duloxetine; sertraline; venlafaxine; citalopram; fluoxetine; escitalopram; trazodone; amitriptyline; paroxetine, nortriptyline, and dosulepin. I share this detail because many readers will be taking, or know someone taking, one of these drugs and you may be interested to know which were most associated with weight gain.

The incidence of taking antidepressants