A Parkinson's drug eased depression's loss of pleasure in a trial

In a single-center trial in Sweden, 85 adults whose depression came with a marked loss of pleasure added the Parkinson's drug pramipexole or a placebo to their usual treatment. Over nine weeks it eased that lost pleasure more than placebo, a moderate effect that held through six months, though pramipexole is an existing drug used off-label here, not an approved depression treatment.

Based on a peer-reviewed study in Nature Medicine

Summary

In a single-center, randomized, double-blind trial in Lund, Sweden, 85 adults with major depression, dysthymia or bipolar depression plus clinically significant anhedonia (a marked loss of pleasure) were randomly assigned to add-on pramipexole or a placebo for 9 weeks; 82 were included in the analysis. Published in Nature Medicine.
The primary outcome was met: pramipexole beat placebo on the anhedonia scale (the Snaith-Hamilton Pleasure Scale, or SHAPS), with a mean difference of -4.04 points (95% CI -6.89 to -1.18; P = 0.006) and a moderate effect size (Hedges g = 0.62).
Two exploratory measures favored the drug too: more light physical activity in daily life and relative preservation of reward-related activation in the ventral striatum, a brain reward hub, consistent with pramipexole acting on the dopamine system.
Improvements in anhedonia were sustained over a 6-month open-label extension, and pramipexole was generally well tolerated; reported concerns include impaired impulse control and daytime fatigue, so it needs medical supervision.
This is one small, single-center trial of an existing drug used off-label as an add-on, targeting anhedonia specifically, not depression in general. It is not an approved depression treatment. Do not start or request pramipexole on the strength of this study; discuss any change in treatment with your doctor.

For some people with depression, the worst part is a kind of numbness. Food, music, friends, sex: none of it lands the way it used to. Doctors call this anhedonia, the loss of pleasure, and it is a core and disabling symptom of mood disorders that standard antidepressants, aimed mostly at low mood, often do little to lift.

Now a randomized trial reported in the journal Nature Medicine has tested a different approach. Researchers gave the dopamine agonist pramipexole, a drug that mimics the brain chemical dopamine, as an add-on treatment or a placebo, once a day for nine weeks. Pramipexole is not new. It has previously been used mainly for Parkinson’s disease and restless legs; here it was added on top of whatever antidepressant or other care they were already taking.

Over those nine weeks, the patients taking pramipexole saw their lost pleasure ease more than the placebo group did, and the gains were sustained during a six-month open-label extension, when everyone could keep taking it.

Why researchers reached for a Parkinson’s drug

Part of the problem is that this is a symptom with limited treatment options. Most antidepressants work on low mood, and for many patients they leave that flatness largely untouched. That gap is what pushed researchers toward dopamine.

Pleasure and motivation depend partly on dopamine, the brain’s way of tagging something as worth wanting. Pramipexole mimics that signal. The idea being tested is that lifting it might give a stalled reward system a nudge in someone whose drive has gone quiet, though that chain of reasoning is still a hypothesis.

How the trial worked

The design is a genuine strength. This was a single-center, randomized, double-blind trial, so neither the patients nor the doctors knew who was getting pramipexole and who was getting a placebo. That guards against wishful thinking on both sides.

It enrolled 85 adults whose major depression, long-running low mood (dysthymia) or bipolar depression came with marked anhedonia, and 82 were included in the analysis. Everyone kept taking their usual care; the study medication or placebo went on top.

That is a small study. Eighty-five people at one center, with the main phase lasting just nine weeks, can point a direction. It cannot settle a question.

What changed

On the main measure, its primary outcome was met: pramipexole beat placebo at easing the loss of pleasure. The difference was moderate: real, but not enormous.

Two other measures, which the authors treated cautiously as exploratory, leaned the same way. Those taking it showed increased light physical activity, moving a little more in daily life, and brain scans suggested they held onto more of the reward-related response in the ventral striatum, a hub in the brain’s reward system.

Overall, it was generally well tolerated compared with placebo.

What it means if you are struggling

The result is promising, and holding up over six months counts in its favor. The caveats are just as serious. This was one small trial at a single center. Pramipexole was layered on top of existing treatment rather than replacing it, and it targeted that lost enjoyment in particular, not depression across the board.

It is also a real medicine with risks worth watching. Marie Asp, one of the researchers at Lund University, was direct about the trade-off: “Although most participants in our study tolerated the drug well, it is important to monitor any side effects, such as impaired impulse control and daytime fatigue.” Dopamine drugs like this need medical supervision, which is one reason a single positive result is no cue to seek the medication out.

So if you recognize this numbness in yourself, the honest answer is not to go asking for pramipexole by name. It is one small, promising study of a medication that is not approved for depression. What to do about that flatness is a decision for you and a clinician who knows your history.

Anhedonia is hard to treat, and this trial is a meaningful step, though one small study at a single center is a long way from a prescription to chase.