Researchers report that news online in The New England Journal of Medicine. They included Gary Sachs, MD, of Massachusetts General Hospital and Harvard Medical School.
The study's results "indicate that careful management of mood-stabilizer medications is a reasonable alternative to adding antidepressant medication for treating bipolar depression," Sachs says in a news release from the National Institute of Mental Health.
Bipolar Depression Study
First, the researchers made sure all of the patients were taking appropriate doses of mood-stabilizing drugs such as lithium. Next, they split the patients into two groups.
One group received an inactive sugar pill (placebo) in addition to their mood-stabilizing drugs.
Patients in the other group received one of two antidepressants -- paroxetine or bupropion -- along with the mood-stabilizing drugs.
Paroxetine is sold generically and under the brand name Paxil. Bupropion is sold generically and under the brand name Wellbutrin XL. The study doesn't specify whether the generic or brand-name versions were used.
Paroxetine and bupropion are commonly used with mood stabilizers to treat bipolar depression, but the FDA hasn't approved any antidepressant to treat the disorder, note Sachs and colleagues.
Both patient groups took their assigned drugs for up to 26 weeks.
During that time, the researchers counted how many in each group had eight consecutive weeks without major mood swings.
No Advantage Seen With Antidepressants
Adding antidepressants to the mood-stabilizing drugs didn't appear to affect the results.
About 23% of the antidepressant group met the study's benchmark (eight consecutive weeks without major mood swings), compared with 27% of the placebo group.
The difference was so small that it was not significant, the researchers note. They found no advantage for either antidepressant over a placebo.
However, the antidepressant group also had no more side effects or manic episodes than the group taking a placebo, the study shows.
The findings "come as a surprise," since European studies have supported antidepressants' efficacy in treating bipolar depression, says an online editorial in The New England Journal of Medicine written by R.H. Belmaker, MD. Belmaker works at Ben Gurion University and Beersheva Mental Health Center in Beersheva, Israel.
Further studies are needed to see if some antidepressants are more helpful than others in treating bipolar depression, Belmaker says.
Sachs and colleagues also call for more research, especially long-term studies since their study was relatively short.
The study was funded by the National Institute of Mental Health. In the journal, Sachs and colleagues note financial ties to various drug companies; Belmaker says he has no potential conflicts of interest.
The study and editorial appear in the journal's "Online First" edition and will be published in its print edition on April 26.