Greater openness is needed to stop clinical drug trials being distorted, leading medical journals have said.
Companies selectively report clinical trial results, medical journals say
In a joint editorial, the 11 journals told researchers and firms to register trials at the start so unflattering or unclear results cannot be covered up.
The journals, including the BMJ, have agreed not to publish studies not registered straight away.
The International Committee of Medical Journal Editors said it was acting as some trial results were being withheld.
The committee's commentary, which is appearing in all their publications, said: "Honest reporting begins with revealing the existence of all clinical studies, even those that reflect unfavourably on a research sponsor's product.
"Unfortunately, selective reporting of trials does occur, and it distorts the body of evidence available for clinical decision-making."
The decision by the journals came after concern that certain anti-depressants may make youngsters more likely to commit suicide.
Last month, GlaxoSmithKline agreed to release information on all its clinical studies to settle a lawsuit filed by New York Attorney General Eliot Spitzer, who had accused the firm of suppressing data on the anti-depressant Paxil.
Journals demanding openness
New England Journal of Medicine
New Zealand Medical Journal
Norwegian Medical Journal
The Annals of Internal Medicine
Croatian Medical Journal
Dutch Journal of Medicine
Journal of Danish Medical Association
Medical Journal of Australia
In a letter to the British Medical Journal, Professor Toshi Furukawa, a specialist in psychiatry based in Japan, said one drug company he had had experience with mislabelled the results of trials into an anti-depressant drug and wrongly categorised others.
He said in one case a child with symptoms of hopelessness and suicidal thoughts, who "punched pictures, broke class and sustained lacerations that required six sutures" was categorised as a case of aggression rather than of having an emotional liability or suicidal tendencies.
The industry has already made moves to address concerns about transparency.
In the UK, the Association of the British Pharmaceutical Industry set up a register on its website just over a year ago and now has eight companies which post their results there.
An ABPI spokesman told BBC News Online the association was sympathetic to the journals' concerns and was confident its list met the demands.
But he added: "I have not seen any scientific evidence that results are not accurate. It is just not in the industry's interests to fiddle results, the truth would be found out in the end."
Elsewhere, a Europe-wide register of all unpublished data is set to become available to regulatory authorities under a new European Union directive.
And on 1 October, an internet-based registry will be launched, containing summaries of findings since 2002, by the US lobby group Pharmaceutical Research and Manufacturers of America (PhRMA).
Caroline Loew, PhRMA's vice president for scientific and regulatory affairs, said the website would make "meaningful clinical trial results available to doctors and patients".
But others remain less convinced. Dr Drummond Rennie, a deputy editor of the Journal of the America Medical Association, expressed doubts that the industry would go far enough.
"Progress is being made, but previous experience suggests that because of inherent conflicts of interest it is unlikely that industry will ever be able to establish a large, common, complete, useful, trustworthy, up-to-date and easily accessible register."