Background: Claims made in advertisements in medical journals might not always be supported by high-quality evidence, and referenced studies may have been sponsored by the pharmaceutical industry itself. We studied to what extent randomised controlled trials (RCTs) support the claims in advertisements in leading medical journals.
Methods: Consecutive unique advertisements were selected from nine different medical journals, and evaluated by 250 medical students using a standardised score form. The quality of RCTs that were referenced in these advertisements was assessed with an instrument based on the Chalmers' score.
Results: 158 RCTs from 94 advertisements were used in the study. In total 55% of the RCTs had a high-quality score, 44% intermediate, and <1% had a low-quality score. Almost 40% of the RCTs had a high-quality score and at the same time supported the claim for which they were cited, while only 17% were also not sponsored by a pharmaceutical company.
Conclusion: RCTs used to support claims in medical advertisements are often not a high-quality and independent source of evidence. This distracts from the credibility of claims in advertisements, even in the high-ranked journals.