Placebo effect lingers even after patients are informed that they’re taking a placebo drug. Source: www.e-magineart.com
The placebo effect is a well-known phenomenon in which a patient unknowingly receives a supposedly ineffective treatment that mimics an actual treatment (i.e. a sugar pill instead of actual medication) but still experiences some measure of relief. A team of researchers at Harvard Medical School chose to take the placebo effect phenomenon one step further. What if the patient knew he or she were receiving a placebo?
In order to examine the effect of knowingly taking a placebo, the researchers chose to treat a condition that would repeatedly and consistently afflict patients. Thus, the study looked at how 66 participants with recurring migraines responded to pills labeled as either “placebo,” “Maxalt or placebo” (Maxalt is a legitimate migraine reliever), or “Maxalt.” Researchers gave participants six experimental envelopes; every two envelopes were labeled with one of the three descriptions. However, the labels were not necessarily accurate (1).
Each envelope contained two sets of pills: one set had the “study drug” enclosed, and the other set had “rescue pills” (pills to be taken 2.5 hours after the onset of the migraine in the event the study drug did not work) enclosed. The study drug was either Maxalt or a placebo, but unbeknownst to the participants, two of the six envelopes were mislabeled (see table below). Participants were instructed to open one envelope at the onset of a migraine (1).
| Envelope Label | Study Drug |
| 1. Placebo | Placebo |
| 2. Placebo | Maxalt |
| 3. Placebo or Maxalt | Placebo |
| 4. Placebo or Maxalt | Maxalt |
| 5. Maxalt | Placebo |
| 6. Maxalt | Maxalt |
As a baseline, participants were asked to rate the pain of their first migraine on a scale of one to ten and not open any of the six envelopes. This baseline served as the control. For the next six migraines, participants opened the envelopes in a specified order and rated their pain after taking the study drug (1).
Unsurprisingly, study drugs that were labeled “placebo” were less efficacious than those labeled as “placebo or Maxalt” or “Maxalt.” “Placebo” labeled drugs reduced pain by 26% while the other two labels reduced pain by roughly 40%. This means even when participants knowingly took a placebo, they still experienced some pain relief. In general, regardless of labels, the Maxalt pill tended to be about twice as effective as placebo pills. Furthermore, all of the pills helped the migraine pain to some degree. However, the most shocking results of this trial are that the Maxalt labeled “placebo” was just as effective in minimizing pain as the placebo labeled “Maxalt,” and that envelopes labeled “Maxalt of placebo” were just as effective as envelopes labeled “Maxalt” (1).
The clinical implications of this trial are still unclear, but the fact that placebos labeled as “Maxalt” were as effective as Maxalt labeled as “placebo” highlights the importance of positive labeling. Labels that influence the expectant efficacy of a drug clearly have an effect on the actual efficacy of the drug. Furthermore, this study reinforces the fact that the mind plays an important role in treatment; thus, perhaps in addition to drugs and surgery, the medical field can learn how to harness the power of perception when treating patients (2).
References:
1. S. Kam-Hansen et al,. Sci Transl Med. 6, 218ra5 (2014).
2. G. Stewart, Migraines and the mystery of the ‘placebo effect’(2014). Available at http://www.webmd.boots.com/migraines-headaches/news/20140110/migraines-placebo-effect?page=2 (18 January 2014).