The Hawthorne effect, sponsored trials, and the overestimation of treatment effectiveness

To determine if the results of rheumatoid arthritis (RA) clinical trials are upwardly biased by the Hawthorne effect.

We studied 264 patients with RA who completed a commercially sponsored 3-month, open-label, phase 4 trial of a US Food and Drug Administration approved RA treatment. We evaluated changes in the Health Assessment Questionnaire disability index (HAQ) and visual analog scales for pain, patient global, and fatigue during 3 periods: pretreatment in the trial, on treatment at the close of the trial, and by a trial-unrelated survey 8 months after the close of the trial, but while the patients were receiving the same treatment.

The HAQ score (0-3) improved by 41.3% during the trial, but only by 16.5% when the endpoint was the post-trial result. Similar results for the other variables were patient global (0-10) 51.9% and 34.6%, pain (0-10) 51.7% and 39.7%, fatigue (0-10) 45.6% and 24.6%. Worsening between the trial end and the first survey assessment was HAQ 0.29 units, pain 0.8 units, patient global 0.8 units, and fatigue 1.1 units.

Almost half the improvement noted in the clinical trial HAQ score disappeared on entry to a non-sponsored followup study, and from 23% to 44% of improvements in pain, patient global, and fatigue also disappeared. These changes can be attributed to the Hawthorne effect. Based on these data, we hypothesize that the absolute values of RA outcome variables in clinical trials are upwardly biased, and that the treatment effect is less than observed.