SSRI antidepressant use potentiates weight gain in the context of unhealthy lifestyles: results from a 4-year Australian follow-up study

OBJECTIVE: To examine the association between antidepressant use and weight gain, as well as the interaction with lifestyle factors. DESIGN: Longitudinal study. SETTING AND PARTICIPANTS: We used data from 2334 adults from two stages (4.4 years apart) of the North West Adelaide Health Study, including validated diet and lifestyle questionnaires, measured body weight and linked pharmaceutical prescription data. MAIN OUTCOME MEASURES: Body weight change. RESULTS: 188 (8.1%) participants had a mean annual number of 1-2 antidepressant prescriptions, and 212 (9.1%) had over two prescriptions. The mean annual weight gain was 0.12, 0.18 and 0.28 kg in non-users, low (1-2 prescriptions/year) and high (>2 prescriptions/year) antidepressant users, respectively. In multivariable regression models, antidepressant use was positively associated with weight gain: high antidepressant users gained an extra 0.22 (95% CI 0.00 to 0.44) kg per year. This association was mainly due to selective serotonin reuptake inhibitor (SSRI) use. High SSRI users gained 0.48 (95% CI 0.20 to 0.76) kg more than non-users. There was no association between tricyclic or other antidepressant use and weight gain. The association between SSRI use and weight gain was stronger among those with high intake of Western diet, greater sedentary activity, and who smoked. CONCLUSIONS: SSRIs use was associated with weight gain in the presence of unhealthy behaviours including Western diet, sedentarism and smoking.