New-generation antidepressants such as Prozac work no better than dummy pills on many depressed people, new research suggests.

A review of clinical trials found they had no more effect than a placebo for mildly depressed patients and for most people suffering severe depression.

Even trials suggesting benefit for severely depressed people did not provide evidence of clear clinical benefit, researchers said.

Dr Tim Kendall, deputy director of the Royal College of Psychiatrists Research Unit, said the findings were "fantastically important".

A group of experts, led by Professor Irving Kirsch, from the Department of Psychology at the University of Hull, analysed 47 clinical trials using data released under Freedom of Information rules by the US Food and Drug Administration (FDA).

The researchers looked at four commonlyused antidepressants and the clinical trials submitted to gain licensing approval.

They included antidepressants regularly prescribed in the UK, including fluoxetine (Prozac), venlafaxine (Efexor) and paroxetine (Seroxat).

They found little evidence of benefit when analysing both unpublished and published data from the drug companies.

Furthermore, the seemingly good results for very severely depressed patients came from the fact a patient's response to the dummy pill decreased rather than any notable increase in their response to antidepressants.

"Drug-placebo differences in antidepressant efficacy increase as a function of baseline severity, but are relatively small even for severely depressed patients," the researchers said.

"The relationship between initial severity and antidepressant efficacy is attributable to decreased responsiveness to placebo among very severely depressed patients, rather than to increased responsiveness to medication."

The researchers said their study was one of the most thorough investigations into the efficacy of new generation antidepressants, known as Selective Serotonin Reuptake Inhibitors (SSRIs).

The paper, Initial Severity and Antidepressant Benefits: A Meta- Analysis of Data Submitted to the FDA, was published in the journal PLoS (Public Library of Science) Medicine.

Professor Kirsch said: "The difference in improvement between patients taking placebos and patients taking antidepressants is not very great.

"This means that depressed people can improve without chemical treatments.

"Given these results, there seems little reason to prescribe antidepressant medication to any but the most severely depressed patients, unless alternative treatments have failed to provide a benefit.

"This study raises serious issues that need to be addressed surrounding drug licensing and how drug trial data is reported."

Dr Kendall said the study was important because it looked at both unpublished and published trial data.

In 2004, Dr Kendall and colleagues examined how drug companies only publish some of their data relating to new drugs.

Writing in The Lancet medical journal, they concluded that published evidence was more favourable than unpublished evidence when it came to looking at the safety of paroxetine and venlafaxine in children and young people with depression.

Only when all evidence was examined did it become clear that the risks (particularly the increased risk of suicidal behaviour) outweighed the benefits, Dr Kendall said.

This study raises serious issues that need to be addressed surrounding drug licensing and how drug trial data is reported Professor Irving Kirsch

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Last updated: 03/28/2008 - 08:46 AM