Selective serotonin reuptake inhibitors (SSRIs) are twice as likely to produce relief of symptoms of obsessive compulsive disorder compared with placebo, according to an article in Issue 1 (2008) of the Cochrane Database of Systematic Reviews.

However, the drugs have a "modest" effect at best, said Dr. Ghulam Mustafa Soomro, lead review author and honorary research fellow at St. George's Hospital Medical School in London.

"Although SSRIs should be considered potentially effective treatments for obsessive compulsive disorder patients, treatment decisions need to take account of the potential adverse effects of these drugs," including nausea, insomnia and sexual dysfunction, he warned.

Many people with the disorder seek out therapy that teaches them to confront, tolerate and gradually wean themselves from obsessive and compulsive behaviors.

"This is the primary kind of therapy used for obsessive compulsive disorder. It teaches patients to pay attention to their internal experiences and tolerate scary thoughts without having to act on them," said Sanjaya Saxena, MD, director of the Obsessive-Compulsive Disorders Program at the University of California, San Diego School of Medicine. "They learn that nothing terrible happens if they refrain from their usual compulsive behaviors."

Nevertheless the success rates for this type of therapy vary, and "unfortunately, about 25 percent of patients offered this form of treatment refuse it," Soomro said, adding that selective serotonin reuptake inhibitors "may offer help to some of these patients."

After reviewing 17 studies that included 3,097 patients, the reviewers concluded that the drugs were more effective than placebo in reducing symptoms 6 to 13 weeks after starting treatment.

None of the drugs stood out above the rest; they all appeared equally effective. However, in most cases, side effects such as nausea and headache were noticeably worse with the antidepressants than with placebo.