Researchers based at the Max Planck UCL Centre for Computational Psychiatry and Ageing Research and the Wellcome Trust Centre for Neuroimaging, UCL Institute of Neurology, have conducted a double-blind placebo-controlled study into the effects of dopamine drugs, the results of which are published in the Journal of Neuroscience.

Healthy people given the common Parkinson’s drug levodopa, which boosts dopamine levels in the brain, were increasingly willing to take risks to get rewards and the drug also affected how happy they were about the rewards they received.

Previous research on the neurotransmitter dopamine has shown that it is involved in learning about rewards, and dopamine drugs can sometimes lead to gambling problems in people with Parkinson’s disease. Thirty healthy adults completed a gambling task in which they chose between safe and risky options and were repeatedly asked, “How happy are you at this moment?” The participants completed two sessions, one after receiving levodopa and one after receiving a placebo.

The same team showed in a previous study that happiness depends not on how well things are going, but whether things are going better than expected. They used functional MRI to identify signals in the striatum, an area with substantial dopaminergic input, that were correlated with how much happiness changed during the task.

In the current study, boosting dopamine increased how happy subjects were after small rewards. On placebo, happiness was higher after large than small rewards. On levodopa, subjects were just as happy about small as large rewards, suggesting that levodopa might lead to similar dopamine release for rewards of different sizes.

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