Prolonged use of antidepressant may lead to increased risk of weight gain associated with high risk of many diseases including diabetes, heart disease and even cancers, say researchers.

The study showed that normal weight and overweight people who took antidepressant for long time had a higher risk of being overweight or obese. "It's important to stress that no patient should stop taking their medication and that if they have any concerns they should speak with their doctor or pharmacist," said lead author Rafael Gafoor from King's College London. According to the researchers, depression is common in obese people resulting in increaseD prescription rate of antidepressant. However, not much has been reported on the impact of widespread antidepressant treatment on weight gain.

The study, published in journal The BMJ, included data from over 300,000 adults with an average age of 51, whose body mass index (BMI). Participants were divided in groups according to their BMI and whether or not they had been prescribed an antidepressant in a given year. They were monitored for 10 years. The results showed that for every 59 people taking antidepressant, one extra person would gain at least 5 per cent weight over the study period.

The researchers also found that the risk increased during the second and third years of treatment as gaining 5 per cent of weight was 46 per cent higher than the general population during the second year of the study. Researchers from the University of Bologna, Italy, emphasised that doctors should give lifestyle advice on diet and exercise to minimize the risk of weight gain and that weight should be measured during antidepressant treatment. They also suggested that while antidepressant treatment should be offered to those with moderate or severe depression, alternative treatment such as group cognitive behavioural therapy may be preferable for people with milder depression.