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Weight Gain and Antipsychotic Medication: Differences Between Antipsychotic-Free and Treatment Periods

J Clin Psychiatry 2001;62(9):694-700

Background: We performed a retrospective analysis of data involving 121 inpatients to examine the rate of weight gain during antipsychotic-free periods and during treatment with various antipsychotic drugs.

Method: Data were analyzed to determine differences in weekly weight change during antipsychotic-free (N = 65), typical antipsychotic (N = 51), or atypical antipsychotic (N = 130) treatment periods. Atypical antipsychotic treatment periods were further subdivided into olanzapine (N = 45), clozapine (N = 47), or risperidone (N = 36) treatment periods. A paired comparison was conducted on 65 patients who had an antipsychotic-free treatment period preceding or following a neuroleptic drug treatment period. In addition, patients were classified as either non-obese (with a body mass index [BMI] <= 29.9 kg/m2) or obese (BMI >= 30.0 kg/m2) to test whether the rate of weight gain during treatment periods was related to initial BMI.

Results: Across all treatment periods, weekly weight gain was as follows: 0.89 lb/wk (0.40 kg/wk) on atypical antipsychotic medication, 0.61 lb/wk (0.27 kg/wk) on typical antipsychotic medication, and 0.21 lb/wk (0.09 kg/wk) on no antipsychotic medications. The atypical antipsychotic versus antipsychotic-free comparison was significant (F = 3.51; df = 2,231; p = .031), while the typical antipsychotic versus antipsychotic-free comparison was not. Among the individual atypical antipsychotic medications, significantly more weight gain occurred during olanzapine treatment (1.70 lb/wk) (0.76 kg/wk) than with either clozapine (0.50 lb/wk) (0.22 kg/wk) or risperidone (0.34 lb/wk) (0.15 kg/wk) treatments (F = 7.77; df = 2,117; p = .001). In the paired analysis with patients serving as their own controls, the difference between weekly weight gain during atypical antipsychotic treatment and antipsychotic-free treatment was significant (t = -3.91; df = 44; p = .001), while the difference between weight gain during typical antipsychotic treatment and antipsychotic-free treatment was not significant. With the individual drugs, treatment with both olanzapine and clozapine caused significantly higher weekly weight gain than antipsychotic-free treatment (p = .001 and p = .036, respectively), while treatment with risperidone did not. Non-obese patients (BMI < 29.9 kg/m2) and obese patients (BMI > 30.0 kg/m2) did not differ significantly in their weight gain during typical or atypical antipsychotic treatment.

Conclusion: Treatment with atypical antipsychotics was associated with more weight gain than treatment with typical antipsychotics. Among the atypical drugs, olanzapine was associated with more weight gain than either clozapine or risperidone. The patient's admission BMI was not associated with the amount of weight gained during subsequent antipsychotic treatment.