Including a placebo arm in a trial is likely to reduce recruitmentBMJ 1999; 318 doi: https://doi.org/10.1136/bmj.318.7191.0e (Published 24 April 1999) Cite this as: BMJ 1999;318:e
Little is known about the effect on recruitment of including a placebo arm in a clinical trial. On p 1114 Welton et al asked postmenopausal women to consider participation in a long term randomised controlled trial of hormone replacement therapy. Half were told about a trial of two treatments, and half were told about a trial of the same two treatments and a placebo arm. The proportion willing to enter the trial with the placebo arm was lower than that willing to enter the trial of active treatments only, but not significantly so. Reasons for wanting to take part were altruism and personal benefit, and reasons for not wanting to take part were reluctance to restart periods, not wanting to interfere with good health, and not wanting to take unknown or unnecessary tablets. Recruitment to trials might be increased if participant information included the potential benefits for others as well as potential personal benefits and risks.