How can a dummy pill have a real effect on your body?

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1. What is the placebo effect?

The placebo effect – when a patient feels better despite taking a medicine with no active ingredient – can be surprisingly strong. Most GPs in the UK have given a placebo to at least one of their patients.

Dummy pills can make a significant difference to conditions like chronic pain. And it's not just pills. Fake acupuncture has been shown to reduce the severity of migraines. And ‘sham’ surgery, where no procedure is actually performed, can also have a potent placebo effect.

The latest science suggests that, even though there are no actual medical ingredients in a dummy pill, real changes are taking place inside our bodies when we take them.

2. Which pill would you take?

The branding, cost and even the colour of pills can make their placebo effect stronger. So which colour pill would you choose?

Red pills

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Red pills

Red pills are more effective for treating pain than white, blue or green pills, and can make the patient feel more awake and lively.

Blue pills

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Blue pills

Blue pills make more effective tranquilizers than red ones. Except for Italian men, for whom blue is associated with their national soccer team!

Green pills

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Green pills

One study reported that green tablets could be up to twice as effective at reducing phobia anxiety as red and yellow ones.

White pills

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White pills

White tablets – especially those labelled "antacid" – are better for soothing ulcers, even when they contain nothing but lactose.

3. Treating Parkinson's with a placebo

Illustration adapted from a representative Parkinson's patient’s brain scan that showed a placebo response in Lidstone et al., Arch Gen Psychiatry, 2010.

Illustration adapted from a representative Parkinson's patient’s brain scan that showed a placebo response in Lidstone et al., Arch Gen Psychiatry, 2010, 67(8):857-865 (click on the link below to read the paper).

Parkinson’s disease has profound physical symptoms, caused by low levels of the brain chemical dopamine. In one study of 35 patients with mild to moderate Parkinson’s, brain scans showed that dopamine levels could be returned to levels close to normal, when treated medically with the dopamine pill L-dopa – but that almost identical results could be achieved with a placebo. It's only one study, but the results do seem to show a real physical effect from taking a dummy pill.

4. Can placebos work if we know what they are?

The common assumption about placebos is that we need to believe they are real medicine for them to work. But that means doctors having to mislead patients about what it is they are taking.

So what happens if your doctor is straight with you, and you know you're getting a dummy pill?

Placebo without deception

In one study, 60% of patients with irritable bowel syndrome (IBS), who knew they were being given a placebo, reported health improvements. That compared to 35% of a control group who were given nothing.

It may be that the ritual of consulting a doctor and receiving pills is enough to trigger the placebo response. A good bedside manner certainly helps. One study found that depressed patients given placebo pills by an empathetic doctor fared better than those taking an active drug from a doctor who expressed no interest in their patients.