Background: To investigate the association of clozapine treatment and weight gain, we studied short- and long-term weight gain, correlation of weight gain with treatment response, and risk factors for weight gain in 82 patients with chronic schizophrenia who received clozapine treatment for up to 90 months.
Method: Weight values were obtained through retrospective chart review. Clozapine was titrated over an average of 3 to 5 weeks up to a dose of 500 to 600 mg/day. Psychopathology was assessed with the Brief Psychiatric Rating Scale and the Clinical Global Impressions scale.
Results: A clinically significant weight gain occurred mostly during the first 6 to 12 months, but continued well into the third year of treatment. Weight gain and treatment response were not correlated, and early weight gain was not a predictor of response. The cumulative incidence of patients becoming substantially overweight exceeded 50%. Being underweight at baseline correlated with maximum amount gained (p = .000), and being overweight at baseline correlated with percentage above ideal weight (p = .006).
Conclusion: Treatment with clozapine is associated with a high incidence of substantial weight gain, posing a potential long-term health risk. Studies are needed of the underlying mechanisms of weight gain, as well as the treatment for this side effect.