Some studies are never published because they have disappointing or negative results.
The researchers might find, for example, that a potential new treatment or intervention appears no better than a placebo dummy pill. Initial excitement about the potential new treatment may fade away.
Other reasons why research may not be published include:
- the researchers may not finish writing a report because they moved on to something new,
- the researchers may not ask a journal to publish their findings, or
- the researchers may find that what they have written is turned down by the editors of a journal.
Not being published is more than a matter of disappointment for researchers.
If trials are not published, there's a risk of other researchers attempting something similar again, with similar results, therefore wasting time.
There is also a danger that while one or more disappointing studies may remain unpublished and invisible, a single positive study will be published which may attract widespread attention.
The publication of the single study may result in the wrong belief that a treatment or intervention is more effective than it really is. The treatment may even be useless or harmful.
Well-designed studies should be published whatever the results, because, disappointing or not, they add to the overall understanding of health and disease.
In order to reduce the risk of the results of studies never being published, and so remaining hidden, most clinical trials now have to be registered when they begin.
On the register
More and more trials are now formally registered. This means that some details are recorded, usually on a publicly accessible website, before they are started. Information about what those details should contain has been established by the World Health Organization (WHO).
Most clinical trials that are publicly funded in the UK, for example by the National Institute for Health Research and the Medical Research Council, have to be registered before they start to recruit people to take part in them.
Many charities also insist on trial registration as a condition for funding the research. The pharmaceutical industry is also committed to registering trials (although for commercial reasons, companies sometimes supply less information than recommended by WHO).
Many of the most important medical research journals, like the British Medical Journal and the Lancet, say they will not publish reports of clinical trials that have not first been registered. This means that research, whether formally published or not, can be identified by those collecting together evidence or planning similar research.
Trial registers, which contain a small amount of information about a trial, reduce the likelihood that trials will be forgotten about, and that unexpected or unwanted results will be overlooked.