Schizophrenia, glycemia and antipsychotic medications: An expert consensus review

Interpretation of the extant data reporting correlations between any or all of the antipsychotic medication and the incidence and prevalence of type 2 diabetes has several limitations. Much of the available published data are case reports or case series without proper controls or are drawn from pharmacy or health-plan databases, with variable control for patient-selection bias, concomitant medications and other risk factors. Moreover, much of the available research is supported by the atypical antipsychotics' sponsors, possibly introducing bias. Furthermore, an inherent relationship between schizophrenia (and perhaps bipolar disorder and depression) and diabetes independent of medication effects is a significant and confounding variable. Notwithstanding, however, a growing confluence of published scientific research suggests that clozapine and olanzapine may disrupt glucose homeostatic mechanisms to a greater extent than risperidone, quetiapine, ziprasidone or aripiprazole in predisposed persons. It remains unclear, however, whether this publication pattern reflects true intrinsic differences with these agents and/or a reporting bias. More long-term, methodologically sound data on these agents will be needed to determine whether different liabilities for the development of type 2 diabetes actually exist. In addition, further studies are also required to gain mechanistic insight into the antipsychotic-associated weight gain and diabetes. In the interim, clinicians are encouraged to familiarize themselves with the available efficacy data in schizophrenia, mood disorders and other psychiatric conditions, and to monitor patients according to recent expert guidelines and position statements from the Canadian Diabetes Association, the American Diabetes Association and the American Psychiatric Association regarding the diagnosis and management of diabetes in psychiatric populations (2, 92, 108-110).