Genes Influence Whether Psych Drugs Lead to Weight Gain

FRIDAY, July 20 (HealthDay News) -- Researchers have discovered two genetic variants associated with substantial, rapid weight gain in people taking antipsychotic medications.

The researchers said the findings could eventually be used by doctors to identify which patients have the variations so they can be treated without the risk of weight gain, which can lead to obesity and health problems including diabetes and heart disease.

"Weight gain occurs in up to 40 percent of patients taking medications called second-generation or atypical antipsychotics, which are used because they're effective in controlling the major symptoms of schizophrenia," Dr. James Kennedy, of the Center for Addiction and Mental Health, in Toronto, said in a center news release.

Kennedy, senior author of a study published online recently in the journal Archives of General Psychiatry, pinpointed a variation near the melanocortin-4 receptor gene, which is known to be linked to obesity.

The study of patients in Europe and the United States being treated with atypical antipsychotics found that those with two copies of the variant gained about three times as much weight as those with one or no copies -- about 13 pounds vs. 4 pounds.

"The weight gain was associated with this genetic variation in all these groups, which included pediatric patients with severe behavior or mood problems, and patients with schizophrenia experiencing a first episode or who did not respond to other antipsychotic treatments," Dr. Daniel Muller, study co-author and Center for Addiction and Mental Health scientist, said in the news release.

"The results from our genetic analysis combined with this diverse set of patients provide compelling evidence for the role of this [melanocortin-4 receptor] variant," Muller said. "Our research group has discovered other gene variants associated with antipsychotic-induced weight gain in the past, but this one appears to be the most compelling finding thus far."

Kennedy and Muller also were involved in another study that identified a different variation near the melanocortin-4 receptor gene that was associated with weight gain in patients taking antipsychotic drugs. The study was published earlier this year in The Pharmacogenomics Journal.

Although the researchers found that the melanocortin-4 receptor gene variant was associated with rapid weight gain, the study did not prove a cause-and-effect relationship.