Placebos work even when you know they don't contain medicine

A review of five studies, involving 260 patients, published last month found that 'open-label' placebos - those that patients know contain no active medication - can improve symptoms in a range of conditions," reports The Guardian.

One Harvard Medical School study gave placebos to 80 patients with irritable bowel syndrome (IBS). Thirty seven patients were told they were being given placebo pills and 43 were given no treatment. Those receiving the placebo had "significantly greater scores than the no-treatment control on the main outcome measure, Global Improvement Scale."

In another study "chronic lower back pain patients openly given dummy pills to add to their existing treatments reported an average 30% pain reduction." The other three open placebo studies "reported reduced symptoms for depression, lower back pain, and attention deficit hyperactivity disorder."

Why do placebos work? The Guardian lists three possibilities:

1. Patients who have had positive experiences with doctors might have "subconscious boosts to levels of endorphins and neurotransmitters," making them feel better.
2. When patients are told that placebos are effective, it could result in "a conscious expectation of improvements, resulting in chemical releases that relieve their symptoms."
3. The embodied cognition effect: "the possibility of improvement can trigger subconscious signals to pass between different parts of the body, resulting in chemical releases that alleviate symptoms."