Most randomized controlled trials for psoriasis used placebo comparators despite the availability of effective treatments

International audienceBackground: The availability of effective treatments for psoriasis raises ethical questions about the use of a placebo group in therapeutic trials. We evaluated the use of the placebo over time in such trials.Methods: From trials in a living Cochrane review and network meta-analysis for psoriasis, we included trials comparing a biologic to a placebo or other systemic treatment. First, we tested the changes in placebo rate from 2001 to 2019 by linear regression, then constructed networks for 2004-2019 and evaluated the contribution of the placebo to the network meta-analysis estimates per trial and per comparison.Results: We included 81 trials (36,774 patients). The placebo rate did not decrease significantly over time. The proportion contribution of trials with a placebo decreased from 100% in 2004 to 86% in 2008 and 75% in 2019. However, the proportion contribution of trials without a placebo remained low (from 0% in 2004 to 25% in 2019).Conclusion: The design of future psoriasis trials should be reviewed to improve the number of patients to be included in a placebo group