Research funded by drug companies is more likely to produce results that favour the sponsor's product, reveals a new study.

Researchers analyzed 30 previous reports examining pharmaceutical industry-backed research and found the conclusions of such research were four times more likely to be positive than research backed by other sponsors.

"What we found was that in almost all cases there was a bias - a rather heavy bias - in favour [of a drug] when the study was industry funded," study leader Joel Lexchin told New Scientist.

The main reasons for this, say the team, may be that positive studies are more likely to be published than negative ones. Also, inappropriate comparison drugs may be used in these trials, skewing findings in favour of the tested product.

The new analysis is published in a special issue of the British Medical Journal, which focuses on the close relationship between doctors and the pharmaceutical industry.

Two to entangle
 

"Doctors, drug companies and most importantly patients would all benefit from greater distance," cautions BMJ editor Richard Smith. "It does of course take two to entangle, and we hope that nobody will see this theme issue as anti-drug company."

But Richard Ley, a spokesman for the Association of the British Pharmaceutical Industry, rejects the study's findings. "The average drug takes 10 to 12 years to develop and costs £350 million - even if you are the most selfish company in the world you can't afford to risk the time and money [to produce biased results]," he told New Scientist.

The clinical trials are overseen from start to finish by independent ethics committees, says Ley, with final checks made by a country's licensing authorities.

Quality scale
 

Lexchin, an expert in pharmaceutical policy, at York University in Toronto, Canada, and colleagues analysed 30 studies examining drug-industry backed trials between 1966 to 2002.