A strong placebo response is apparently more often caused by people’s expectations coming into a randomized, blinded clinical trial, than it is caused by the supportive care that surrounds all the trial participants, according to a study in the British Journal of Psychiatry.
A team of UCLA researchers randomized 88 participants to 8 weeks of treatment with supportive care alone, or supportive care combined with double-blind treatment with placebo or antidepressant medication. They measured the participants’ expectations of medication effectiveness, their response to treatment, and their therapeutic alliance with the practitioners involved.
Antidepressant or placebo, when combined with supportive care, did not have significant differences in their therapeutic effects on participants. However, both groups had better outcomes than those who received supportive care alone without a medication or placebo pill.
“Medication expectations uniquely predicted placebo treatment outcome and were formed by time of enrolment, suggesting that they were shaped by prior experiences outside the clinical trial,” concluded the researchers.
(Abstract) Role of pill-taking, expectation and therapeutic alliance in the placebo response in clinical trials for major depression (Leuchter, Andrew F. et al. British Journal of Psychiatry. December 2014. DOI: 10.1192/bjp.bp.113.140343)