Psychiatric drugs are reported to be about 50 per cent more effective in
After scientists conduct a study, they can send their papers to scientific journals for review.
If the papers are accepted, they are then published and cited in the drug review and approval process. But many trials are never published.
In this research, Oostrom was able to identify 77 trials of drugs that were conducted but never ended up being published in scientific journals.
Adding these unpublished papers to the analysis changed the results.
“Trials funded by manufacturers in which their drug appears more effective are more likely to be published. That connection between outcomes and publication doesn’t appear to happen as much when there are other funders,” Oostrom said.
In her analysis, she found that adding just one of each of the unpublished trials reduced the sponsorship effect by 20 per cent.
“The addition of unpublished trials reduces the effect of sponsorship, and most of the sponsorship effect can be explained by publication bias,” she said.
There is one major policy that has helped reduce the problem of publication bias in the past two decades – preregistration, she said.
Preregistration requires researchers to register their trials as a condition of publication or funding.
Requirements often include requiring researchers to report their results, which can increase the possibility that even studies that aren’t favorable to the target drug see the light of day.
Oostrom found that the sponsorship effect has declined since 2005, when preregistration started becoming required for some trials, and when other transparency and publication norms began changing.
But preregistration is not a cure-all. Even with current preregistration requirements, only one-quarter of all preregistered trials report results.
And it doesn’t fix what has gone on in the past.
“Most existing antidepressant and antipsychotic drugs were approved before these requirements, so even with preregistration, there is a stock of existing drugs potentially based on biased evidence,” she said.
