But will this treatment result in the development of diabetes? This is the controversial question which Dr. Richard Petty addressed recently during a lecture in Atlanta, Georgia which was beamed live in the Philippines and other Asian countries.
According to Petty, there has been a vigorous and confusing debate about the relative risks of diabetes and hypercholesterolemia with different antipsychotic agents. In recent years, an increasing number of cases of diabetes mellitus in people suffering from major mental illnesses was observed.
A study published in the British Medical Journal suggested that antipsychotic drugs, particularly the so-called atypical drugs, may cause metabolic side-effects such as diabetes.
However, Petty, an endocrinologist and professor at the Promedica Research Center in Georgia State University’s College of Health Sciences, explained that there were many reports of abnormalities of carbohydrate metabolism occurring with higher than expected frequency in patients with psychotic and mood disorders long before the advent of antipsychotic agents. These included delayed responses to insulin and glucose tolerance test suggestive of insulin resistance and a predisposition to diabetes.
In contrast to the belief that antipsychotic drugs cause diabetes, another study published in the American Journal of Psychiatry showed that majority of the patients with mental illness are insulin-resistant. "It was also found that 15 percent of these patients already have pre-diabetes or what we call impaired fasting glucose. These patients are not yet given medication so how can we say that the drugs are causing the problem?" Petty argued.
Petty also presented a study conducted by Promedica Research Center which conducted a diabetes risk assessment on 125 patients. Based on the results of the study, it was shown that patients developed diabetes regardless of what antipsychotic drug they were taking. "The similar number of patients developing diabetes while on such chemically different medicines strongly suggests that the diabetes associated with mental illness is not drug-related. Clearly, these drugs may unmask rather than cause diabetes in predisposed individuals," said Petty.
Rather than treatment-related, Petty said that family history and lifestyle remain to be the most important predictors of diabetes among patients with schizophrenia and other mental illness. "It is also important to note that the increased prevalence of type-2 diabetes associated with mental illness is not confined to the sufferers themselves. It is quite clear that patients with schizophrenia have relatives with type-2 diabetes," he said.
Stress could also be a factor in the development of diabetes. Stress increases steroid level and may make some patients overeat. As a consequence, more fat is deposited in the abdomen and other parts of the body. "Fat constantly breaks down releasing fatty acids and triglycerides. This stimulates the pancreas to release insulin. As a consequence, the insulin level rises and patients may also develop insulin resistance," said Petty. Insulin resistance is one of the risk factors of diabetes.
Petty recommended that psychiatrists should stick to the drug which works best for their patients. He specifically recommended olanzapine because of the drug’s efficacy in treating the psychologically disabling symptoms of schizophrenia.
Olanzapine is also proven to reduce hostility in patients, a beneficial effect which can be attributed to the prolactin-sparing mechanism of the drug. Prolactin is a hormone which has 300 functions in the body, including lactation or breast milk production. An elevated prolactin level, however, among patients with schizophrenia is associated with hostility.