Are Antidepressants Effective?

July 10, 2002 -- In the 14 years since they hit the market, Prozac, Paxil, and the other SSRIs have changed the face of depression treatment. Some 7 million Americans now take the antidepressant drugs for everything from generalized anxiety to PMS, but there is growing evidence that their effectiveness may be more marketing hype than miracle cure.

The latest scientific study to weigh in on the subject finds that the antidepressants worked only marginally better than placebos in a group of studies submitted to the FDA. Study participants taking the dummy pills had approximately 80% of the response seen in patients taking one of the six most widely prescribed antidepressants.

Lead researcher Irving Kirsch, PhD, tells WebMD that in many of the studies, while the difference between drug and placebo was significant from a statistical standpoint, it did not represent a significant difference for patients. His study appears July 15 in the American Psychological Association's electronic publication, Prevention and Treatment.

"We are not saying that people don't respond to these medications," says Kirsch, who is a psychology professor at the University of Connecticut. "On the contrary, the response is very large, and that is why there has been this so-called revolution in the treatment of depression. The catch is that the response to placebo is almost as large."

Selective serotonin reuptake inhibitors (SSRIs) are believed to relieve depression by increasing the effectiveness of the neurotransmitter serotonin in the brain. In a review published four years ago, Kirsch first suggested that the antidepressants are just slightly more effective than a placebo. The findings were widely criticized by mental health professionals at the time, and Kirsch says the latest review attempts to address the criticisms.

Kirsh and colleagues pooled data from roughly 40 studies of six SSRIs that won FDA approval between 1987 and 1999. The drugs included Prozac, Paxil, Zoloft, Celexa, Effexor, and Serzone. All of the studies compared depression relief among patients treated with the SSRIs with those given placebos. The patients were not told which treatment they were getting, and both groups improved. Using a standardized 50-point depression scale, the pooled results showed that patients treated with antidepressants had a 10-point improvement, while those given placebos improved by 8 points.

Kirsch concedes that the design of the placebo-controlled studies may mask the true effectiveness of the antidepressants and overstate the effectiveness of the placebos. But he adds that the finding also clearly suggests that too many people are relying on unproven drugs to treat the symptoms of depression.

"People may be better off exploring other treatment options such as psychotherapy or exercise, which has been shown to reduce depression. And the side effect of physical exercise is better health. That is much better than the loss of sexual function, tremors, agitation, diarrhea, and nausea that are side effects of SSRIs."