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A study by Yale psychiatrists indicates that newer schizophrenia drugs tend to increase patients’ risk for diabetes, giving physicians both legal and clinical incentives not to prescribe them.

Psychiatry professors Douglas Leslie and Robert Rosenheck analyzed data collected on schizophrenia patients and discovered a higher rate of diabetes among those who take newer antipsychotic medications, which generally have fewer side effects than older drugs. Evidence also points toward a slightly higher risk of a potentially fatal insulin deficiency called diabetic ketoacidosis. The study, published in the Sept. 2004 issue of the American Journal of Psychiatry, confirms a link between elevated diabetes risks and the newer generation of drugs.

Leslie and Rosenheck analyzed the records of schizophrenia sufferers in the Veterans Affairs hospital system who were taking atypical antipsychotic drugs. According to the study, 4.4 percent of the patients in the sample developed diabetes over the course of the 14-month survey, a proportion nearly seven times that of the general population.

The authors attribute no more than two percent of this increased risk to the new drugs, as one of the medications analyzed showed an increase of only 0.05 percent. According to the study, the higher level of diabetes among the test population may be due to a number of other factors including “poorer overall physical health, less healthy lifestyles, or poorer access to healthcare services.”

Leslie and Rosenheck could not be reached for comment.

But some say the already-at-risk veterans population might actually mask the link between newer antipsychotic drugs and diabetes.

“The sample does not represent the general population,” said Henry Nasrallah, a professor of psychiatry, neurology and neuroscience at the University of Cincinnati. “It’s one of the few that shows no difference among the atypical [medications].”

Nasrallah said studies of samples that are more representative than the Yale researchers’ population show a larger discrepancy among various drugs. He said physicians have been quick to change their habits, eschewing riskier medications such as clozapine and olanzapine in favor of newer but relatively untested drugs like ziprasidone and aripiprazole. This conservative medical shift stems from a focus on patient safety as well as a desire to avoid malpractice lawsuits, he said.

“We live in a litigious world,” Nasrallah said. “Lawyers are watching.”

Treatment practices could change again by next year. In December, the Clinical Antipsychotic Trials of Intervention Effectiveness — a large study aimed at determining the long-term effectiveness and side effect of new antipsychotic medications — will be complete. The largest and most thoroughly randomized study to date, it could provide a conclusive answer to the question of whether diabetes is related to atypical schizophrenia medications.

However, doctors are not waiting to prescribe what they view as more effective treatments.

“For clinicians, they don’t need to read the literature,” Nasrallah said. “They can see [the greater risk] in their patients. I can see it in mine.”