Placebos can effectively mimic the results of active medicines if Parkinson’s disease patients have a strong expectation of therapeutic benefit, according to the Canadian Pacific Parkinson’s Research Centre.

Patients who believed they had a 75% probability of receiving active medication experienced maximal dopamine release, far higher than those who thought they had a higher chance of receiving a placebo.

After telling patients the chance they had of receiving a placebo, researchers measured the resulting dopamine release using raclopride positron emission tomography.

Researchers found that having an expectation of therapeutic benefit was important in the levels of dopamine released.