The finding has been revealed after an international research carried out a systematic review for The Cochrane Library.

The researchers have also found that even though these results get published, they would take between one to four more years to appear in journals than studies showing positive results.

"This publication bias has important implications for healthcare. Unless both positive and negative findings from clinical trials are made available, it is impossible to make a fair assessment of a drug’s safety and efficacy," says lead researcher, Sally Hopewell of the UK Cochrane Centre in Oxford, UK.

The findings of one of the five studies in the review suggested that it’s the investigators, and not editors, that are to be blamed for such partiality.

This is because the reasons most commonly given for not publishing were that investigators thought their findings were not interesting enough or did not have time.

"The registration of all clinical trial protocols before they start should make it easier to identify where we are missing results," said Kay Dickersin from Johns Hopkins University in Baltimore, USA, another of the researchers on this project.

One of the other researchers, Kirsty Loudon, based in Scotland, added: “Registration of trials and their results would help people conducting systematic reviews to look at both published and unpublished evidence, to reach reliable conclusions."