Drug companies are placing depressed patients at risk by not publishing negative results from clinical trials and distorting the evidence doctors use to decide which drugs to prescribe.

New research published in The New England Journal of Medicine found nearly a third of the 74 industry-sponsored studies of antidepressants they examined were not published, most of which showed negative outcomes for the drug involved. Not only were positive results 12 times more likely to be published, but negative results were often written so as to convey a favourable outcome.

Researchers warn that selective reporting of clinical trials can lead to misrepresentation of the benefits and risks of a drug and could mislead healthcare professionals into believing some drugs are more effective and less harmful than they actually are, which could place patients at risk.

The published articles suggest 94 per cent of the trials conducted had positive results, whereas analysis by the FDA found only half were favourable.