Antidepressants, which are widely prescribed with mood stabilizers to treat patients with bipolar disorder, do not work in relieving the depressive symptoms of the illness, a large federal study reported yesterday.

The study in the New England Journal of Medicine narrows the already limited number of treatments for bipolar disorder, which affects 5.7 million adults in America, experts said.

“A new generation of drugs is needed,” said Dr. Thomas Insel, director of the National Institute of Mental Health. “It is clear from this data that antidepressants are not the answer.”

Still, some doctors said antidepressants would continue to have a role because there are so few options, and the drugs seem to alleviate other distressing symptoms that often accompany the disorder.

“Many people we see are refractory to a mood stabilizer alone and adding an antidepressant markedly improves them,” said Dr. Lori Altshuler, professor of psychiatry at the University of California, Los Angeles, who was not involved in the study.

But Dr. Altshuler, who has consulted for companies that market drugs for psychological disorders, said the study clearly demonstrated that patients should first try a mood stabilizer, which can also have antidepressant effects.

People with bipolar disorder experience severe mood swings between depression and mania, a state marked by an excess of energy and restlessness. Symptoms of the disorder can interfere with daily activities, and severe cases carry a risk of suicide.

Standard treatment consists of mood stabilizers such as lithium, valproate, and carbamazepine. Antidepressants are often added to control severe depressive swings, despite concerns the drugs might trigger a switch to a manic episode.

Researchers estimated that 50% to 70% of people with bipolar disorder take antidepressants, although the Food and Drug Administration has approved none of the drugs as a treatment for the disorder.

The study, part of the NIMH’s $27 million Systematic Treatment Enhancement Program for Bipolar Disorder, or STEP-BD, set out to determine whether common antidepressants Wellbutrin and Paxil would enhance the benefits of mood-stabilizer drugs. The study was also designed to find out if the antidepressants would trigger mania.

Previous studies had provided mixed results on their effectiveness. Wellbutrin and Paxil were chosen for the study because earlier studies indicated they were less likely to trigger mania than other antidepressants.

The study, designed to mimic real-world conditions, differed from a typical clinical trial in that many patients had complicating disorders, including anxiety, substance abuse, or psychosis.