1. It doesn’t have to be a secret.
Some think it only works if you don’t know you’re taking it. But people with irritable bowel syndrome who knowingly receive a placebo do better than those left untreated.
2. It works better if it’s expensive.
A placebo pill’s pain-killing power is greater among people told they are taking a full-price version, compared with those told the pill is discounted.
3. Animals can get it too.
In a 2012 study, between 30 and 40% of rats experienced pain relief when their morphine injections were swapped for saline.
4. It has an evil twin.
The nocebo effect makes people more likely to suffer from side effects if they are warned about them by their doctor.
5. Your personality could give it away.
Traits like being extroverted, agreeable and open to new experiences appear to be linked with placebo susceptibility.