June 2003
Two related University at Buffalo studies examining the incidence of diabetes and related conditions among patients suffering from schizophrenia or bipolar disorder indicate that it is the illness -- not the atypical antipsychotic medications used to treat the disorders -- that contributes to the increased incidence of diabetes in these patients.
The findings suggest that the atypical antipsychotics, second-generation antipsychotic medications that became available after 1991, such as Clozaril (clozapine), Zyprexa (olanzapine), Risperdal (risperidone) and Seroquel (quetiapine fumarate), may actually have a protective effect against diabetes.
The results seem to contradict growing fears that antipsychotic medications cause the increased rate of diabetes in patients with these mental illnesses, fears that recently led Japan and the European Union to require one atypical antipsychotic to include warnings about diabetes-related complications in its product information sheets.
The studies were conducted by researchers in the Department of Pharmacy Practice in the UB School of Pharmacy and Pharmaceutical Sciences.
Based on the findings, the UB researchers conclude that psychiatric care for patients with the two disorders should be modified to include routine screening for diabetes (adult onset or type 2), hypertension and obesity. They also suggest that severe mental illness should be listed, along with family history of diabetes, as a primary risk factor for diabetes.
"According to our findings in these studies, an association between schizophrenia and bipolar disorder and diabetes seems to exist independent of any antipsychotic use," said Terrance Bellnier, R.Ph., assistant clinical professor of pharmacy practice, director of psychiatric pharmacy practice at UB and co-author of the study.
"The question is, whether these drugs induce diabetes at the same rate, or it's the mental illness itself -- what we're using the drugs for -- that induces diabetes," Bellnier said. "That's the question we tried to answer."
More than 2 million Americans suffer from schizophrenia and the same number suffer from bipolar disorder. Diabetes is estimated to affect more than 15 million Americans.
Data in the study to be presented at the annual conference of the American Psychiatric Association demonstrate that an increased incidence of diabetes among patients with schizophrenia or bipolar disorder predates the use of antipsychotic medications to treat the disorders.
That study, based on a retrospective review of medical data for 569 randomly selected patients with the two disorders admitted to a state psychiatric hospital between 1940 and 1950, before antipsychotic medications were available, found that metabolic disturbances were significantly greater in those patients than among the general population.
According to the results, the rate of diabetes among the patients was 20.9 percent, or 10 times that reported at that time for the general population. The incidence of hypertension was 29.1 percent, compared to 16.5 percent in the general population, and the incidence of "overweight" was 28.2 percent versus 21.8 percent in the general population.
The other UB study compared in a matched-pair analysis the data for these untreated patients with data from 569 patients admitted to a state psychiatric hospital between 1999 and 2002, all of whom were treated with atypical antipsychotics.
