On Jun. 30, 2025, a University of Oxford led study reported that a drug used for Parkinson’s disease has been shown to be effective in reducing the symptoms of difficult to treat depression.

In the largest clinical trial to date, pramipexole was found to be substantially more effective than a placebo at reducing the symptoms of treatment resistant depression (TRD) over the course of nearly a year, when added to ongoing antidepressant medication.

The trial, supported by National Institute for Health and Care Research (NIHR) and published in The Lancet Psychiatry, included 150 patients with treatment resistant depression, with equal numbers receiving 48 weeks of pramipexole or a placebo, alongside ongoing antidepressant medication.

Overall, the group taking pramipexole experienced a significant and substantial reduction in symptoms by week twelve of treatment, with the benefits persisting over the course of a year. However, there were also significant side effects, such as nausea, sleep disturbance and dizziness, with around one in five people on pramipexole dropping out of the trial as a result.

Previous research into using the drug for depression had shown promise, but there had been limited data on its long-term outcomes and side effects until now.

These findings on pramipexole are a significant breakthrough for patients for whom antidepressants and other treatments and therapies have not worked. ‘Pramipexole’ is a medicine licensed for Parkinson’s disease and works by boosting the brain chemical dopamine.

This differs from the majority of other antidepressant medications which act on brain serotonin and may explain why pramipexole was so helpful in this study.