In the future, before you decide to go to an alternative medicine practitioner, it might save you money to get your COMT polymorphism checked.

This is going to make trial designs a little different in the future--how many of each group has the COMT polymorphism will matter (since if you have more in the placebo group, your treatment effect will be less).

Catechol-O-Methyltransferase val158met Polymorphism Predicts Placebo Effect in Irritable Bowel Syndrome international team randomized 104 patients with irritable bowel syndrome (IBS) into one of three groups: sham acupuncture plus interaction with a supportive, encouraging health professional (augmented-placebo); sham acupuncture alone (limited-placebo); or no sham acupuncture or other treatment (waitlist). Relief of IBS symptoms, as defined by responses on a validated scale, was greatest in the augmented-placebo group, intermediate in the limited-placebo group, and least in the waitlist group.

A common polymorphism increases the amount of dopamine available in the prefrontal cortex, which augments the reward response. The investigators found that participants who harbored two copies of this polymorphism had the greatest response to placebo of both types, those with one copy had intermediate responses, and those with no copies responded to neither type of placebo. For example, the improvement in the IBS symptom scale for participants with 2, 1, and 0 copies of the polymorphism in the augmented-placebo group were 140, 100, and 20 points, respectively (on a 500-point scale), whereas the genetic polymorphisms had no effect on outcomes in the waitlist group. In this study, about one quarter of patients had two copies of the polymorphism, one half had one copy, and one quarter had no copies.