For many people who suffer from depression, the condition is not just about feeling down but also about a loss of motivation and difficulty finding pleasure in activities they used to enjoy. A new study conducted in Sweden shows that a medicine used to treat Parkinson’s disease can be used as an add-on therapy to alleviate these symptoms in some patients with treatment-resistant depression. The study has been published in Nature Medicine.

The researchers at Lund University and the psychiatric services in Region Skåne have identified the potential new therapy for the condition associated with depression that involves a reduced ability to feel joy, pleasure or motivation—known as anhedonia. Those affected may lose interest in things that they previously found meaningful or rewarding.

The study is an example of what is known as drug repurposing, whereby an already approved medicine is used to treat a different condition. In this study, the researchers investigated pramipexole, which has long been used to treat Parkinson’s disease, as an add-on therapy for depression with marked anhedonia.