The pill that works when you know

Reader's question: 'My aunt has had back pain for years. She read about "honest placebos", pills that you're told contain no medicine, and she wants to try them. Isn't that a waste of money? How can a sugar pill work if you know it's a sugar pill?'

The doctor replies: It's a fair question, and until fairly recently most doctors would have asked the same. The placebo effect is well known. Patients given a sugar pill often feel better simply because they believe it's real medicine. For that reason, placebos were always linked with deception. It seemed obvious that telling patients the truth would destroy the effect.

In 2010, a team at Harvard tested that idea. They gave people with irritable bowel syndrome, a painful gut condition, a bottle of pills and told them plainly that the pills had no active ingredients. Many of them reported fewer symptoms than a similar group who got no treatment. Later studies on chronic back pain and on tiredness in cancer patients found similar results, though the improvements were usually modest.

Nobody knows for sure why it works, and the jury is still out. One idea is that the ritual itself helps. Taking a pill at the same times every day may remind your body and mind that you're being looked after. Another is that attention matters. Patients who feel listened to tend to feel less stressed, and stress can make pain worse.

Your aunt should know the limits. Placebos can't shrink a tumour, bring down a fever or cure an infection. They seem to help mainly with symptoms that the brain helps to shape, such as pain, tiredness and nausea. She shouldn't stop any treatment she's already on.

If she wants to try, she should talk to her own doctor first and treat the pills as an extra, not a replacement. Honest placebos are cheap and have no side effects. At worst, she'll have spent a little money on sugar. Tell her not to expect a miracle, and suggest she keeps a simple diary of her pain so she can see whether anything changes.