Researchers say unpublished studies show Prozac and three similar drugs have significant results only in the most severely depressed.

This is the VOA Special English Health Report.

A study has raised new questions about the effectiveness of several popular drugs for depression. These antidepressants are known as selective serotonin reuptake inhibitors. 

		Prozac is a popular S.S.R.I.

S.S.R.I.s are designed to help keep serotonin, a brain chemical, at a continuous level.  The new study suggests that they provide little help to the large majority of the millions who take them.

Scientists from Britain, Canada and the United States did the study. It was a meta-analysis, a study of studies.

The team used an American law, the Freedom of Information Act, to get unpublished reports on thirty-five clinical trials of four drugs. Drug companies gave these and published studies to the Food and Drug Administration for approval of the medicines.

In the clinical trials, people with depression were treated with either an antidepressant or a placebo, a pill that contains no medicine. They did not know which they got.

The new report says those who received medicine did improve. But comparable numbers of those who received placebos also improved. The report says the drugs had meaningful results only in the most severely depressed patients.

The two best-known drugs in the study were fluoxetine, better known as Prozac, and paroxetine, sold in the United States under the name Paxil. The other drugs were venlafaxine and nefazodone. 

The Public Library of Science published the findings last month in the journal PLoS Medicine.

Benedetto Vitiello is a psychiatrist at the United States National Institute of Mental Health. Doctor Vitiello, who was not involved in the study, says the findings came as no great surprise. He says psychiatrists have known for years that S.S.R.I.s work best in the sickest patients.

But he says it is important for people who need help not to delay seeking help as a result of the new report.

Critics of the report say S.S.R.I.s can take more time to begin working than the studies permitted. They also note that doctors sometimes try several antidepressants on a patient before choosing one for treatment. 

Future antidepressants might have targets other than serotonin. Scientists funded by the National Institute of Mental Health have found that an enzyme called GSK3B might play a big part in depression. They found that mice with low serotonin levels and signs of depression improved when the enzyme was blocked.

And that's the VOA Special English Health Report, written by Caty Weaver. I'm Mario Ritter.