It’s hard to ignore the fact that ­antidepressant use and obesity in the UK are rising alongside each other. Weight gain is an effect many patients are unhappy about. Sadly, we don’t know much about a link between antidepressants and putting on weight.

Doctors need more information to guide patients who gain weight as it can lead them to stop taking their medication and therefore risk
a relapse.

Weight gain itself may sometimes be a symptom of psychiatric illness. Mentally unwell patients have a higher risk of weight gain through inactivity, lack of energy and loss of motivation.

We do know that taking anti-psychotic drugs can result in putting on weight, but the association between antidepressants and weight gain is not cut and dried.

Patients prescribed antidepressants are therefore vulnerable to obesity simply by virtue of being depressed, taking the antidepressant and being part of the UK population where obesity rates are constantly rising. In an attempt to clarify these muddy waters, Rafael Gafoor, researcher at Kings College, London, joined a study team investigating this link.

Reporting in the British Medical Journal, the results of their research show that antidepressants really are associated with an increased risk of weight gain. Surprisingly, the peak in weight gain came not at the beginning but about two to three years after ­antidepressants were prescribed.

This risk is elevated for up to six years when the focus on weight gain prevention is no longer top of the list of priorities for patients.

There is some evidence that ­particular antidepressants are more likely to be associated with weight gain than others and alternatives should be sought.

This research is important for patients as well as doctors because they can take an active role in managing the possibility of weight gain when prescribed an antidepressant.

Patients and doctors can work as a team to come up with a weight-management plan with both pledging to be vigilant.

If, for instance, there’s a risk of a 5% weight gain (3.5 kg, about half a stone for a 70kg person), this will sometimes be enough to move patients from overweight to obese, or from obese to severely obese, with the attendant risk of heart disease and diabetes.

This new timetable will help patients and doctors plan for the delayed risk of weight gain, and in doing so, enable patients to continue taking antidepressants and, ultimately, lead to better mental health.