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Can J Psychiatry. 2003 Nov;48(10):689-94.

Risk of weight gain associated with antipsychotic treatment: results from the Canadian National Outcomes Measurement Study in Schizophrenia.

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Mood Disorders Psychopharmacology Clinic, Department of Psychiatry, University of Toronto, University Health Network, Toronto Western Hospital, 399 Bathurst Street, Toronto, ON M5T2S8.



Antipsychotic-induced weight gain occurs in a substantial percentage of treated persons. There remains a paucity of naturalistic data that describe relative weight-gain liability with the available novel atypical antipsychotics (NAPs). This investigation describes comparative NAP-induced weight gain in a prospective naturalistic cohort of persons with schizophrenia and related psychotic disorders.


The Canadian National Outcomes Measurement Study in Schizophrenia (CNOMSS) is an ongoing prospective, longitudinal, naturalistic study involving 32 academic and community sites across Canada. Persons with DSM-IV-defined schizophrenia, schizophreniform or schizoaffective disorder, and psychosis not otherwise specified were consecutively enrolled. The overarching objectives of this initiative were to collect and compare global effectiveness, tolerability, safety, and humanistic outcomes in persons receiving commercially available NAPs in Canada. This analysis reports only weight change with the respective NAPs. Other outcomes were reported in separate companion papers.


A spectrum of weight-gain liability was noted with quetiapine (QUE) (mean 7.55 kg, SD 9.20; P = 0.28), olanzapine (OLZ) (mean 3.72 kg, SD 0.56; P = 0.15), and risperidone (RIS) (mean 1.62 kg, SD 7.72; P = 0.43). Categorically defined weight gain (that is, over 7% of baseline weight) was observed in 55.6% of QUE patients, 24.1% of OLZ patients, and 23.7% of RIS patients. Adjusting for demographic and disease-specific confounding factors, QUE patients had greater odds of gaining over 7% of their baseline weight compared with RIS patients (odds ratio [OR] 3.62; 95% CI, 1.02 to 12.83; P = 0.05). No statistical difference was detected between OLZ patients and RIS patients for over 7% of baseline weight (OR 1.54; 95% CI, 0.63 to 3.75; P = 0.12) or over 10% weight gain (OR 1.44; 95% CI, 0.50 to 4.13; P = 0.58).


Clinicians are reminded to monitor anthropometric and metabolic parameters in all NAP-treated persons. Clinically significant differences in weight gain liability exist among the available NAPs.

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