March 3 (Bloomberg) -- Tamoxifen, the generic breast cancer drug, may help control mania in people with bipolar disorder, a study suggests.

The 29 people in the study who took tamoxifen with the anti-anxiety drug lorazepam were less irritable, less aggressive and slept better after three weeks, compared with the 21 patients who took lorazepam alone, according to a study in the March issue of the Archives of General Psychiatry.

Tamoxifen's success at controlling mood may lead to new drugs specially aimed at mental illness, said lead study author Aysegul Yildiz. Mania and depression are the poles in bipolar disorder, which affects about 5.6 million American adults, according to the National Institute of Mental Health. Mania symptoms include heightened activity, sleeplessness and aggression.

``This definitely provides a new treatment option,'' said Yildiz, an assistant professor at Dokuz Eylul University Medical School in Izmir, Turkey.

Tamoxifen works against some breast cancer tumors by blocking the hormone estrogen that feeds them. It also inhibits nerve cell communicators called protein kinase c, implicated by earlier research in bipolar disorder. Tamoxifen is the only protein kinase c inhibitor available for humans, the study said.

``By focusing on this target, we can develop treatments which will be more effective in a shorter period of time,'' Yildiz said in a telephone interview.

Proof of Concept

Everyone in the study took the generic tranquillizer lorazepam. Patients who also took tamoxifen instead of a placebo decreased their dosage of lorazepam 2.5 times faster.

``This is clearly a successful proof-of-concept study,'' said Gary Sachs, the founder and director of Massachusetts General Hospital's bipolar clinic and research program, in a telephone interview. He wasn't involved in the study.

Bipolar disorder often damages relationships and sabotages job and school performance, said Mauricio Tohen, a researcher at Eli Lilly and Co. Treatments include Eli Lilly's Zyprexa, Johnson & Johnson's Risperdal and generic lithium.

Tamoxifen's side effects can include menopause in women, Sachs said.

To contact the reporter on this story: Elizabeth Lopatto in New York at elopatto@bloomberg.net.

Last Updated: March 3, 2008 16:37 EST