Objective: To examine annual weight-development in a sample of 215 psychotic patients treated with risperidone over 5 years.

Method: Naturalistic longitudinal study.

Results: The sample was more obese than the general population at baseline, but also increased much more in mean body mass index over approximately the same time period, while patients off medication seemed to remain weight stable. Excessive weight gain (>7%) was experienced by 40.2% and was weakly associated with weight at baseline (beta = -0.2%; P = 0.02), while independent of gender, symptoms, years of illness, prolactin levels and nicotine consumption. In patients with complete weight data (n = 87), approximately 72% (3.4 +/- 8.3 kg) of the observed 5 years weight gain (4.7 +/- 11.6 kg) had been accumulated after 2 years.

Conclusion: Antipsychotic drug treatment resulted in significant weight gain, which levelled off over time. Unfortunately, few significant predictors of adverse weight development could be identified, leaving little guidance for clinical decision making regarding this specific side-effect.