Could a Parkinson's drug help treat a key symptom of depression?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Age between 18 years and 75 years. * Informed consent * Diagnosis of unipolar depressive episode or bipolar disorder in depressive phase or dysthymia. * Clinically significant anhedonia symptoms: SHAPS self-report score 3 or 4 on ≥ 3 items. * Ongoing stable treatment with at least one antidepressant or mood stabilizing medication for at least 4 weeks. Has tried an antidepressant at a therapeutic dose but not achieved remission (refractory stage 1 depression) Exclusion Criteria: * Ongoing pregnancy, breastfeeding or planned pregnancy. * High risk of suicide according to the overall clinical assessment of the research physician. * Substance abuse within the last 6 months. * Diagnosis of current psychotic disorder. * Known diagnosis of Emotionally unstable personality disorder. * Ongoing treatment under the Compulsory Psychiatric Care Act. * Medical history or strong clinical suspicion of impulse control disorder (including current binge-eating disorder) or a current Attention Deficit Hyperactivity Disorder diagnosis with hyperactivity. * Diagnosis of intellectual disability, dementia, or other circumstances that makes it difficult to understand the meaning of participating in the trial and provide informed consent. * Diagnosis of renal failure (eGFR \< 50 ml/min/1.73m2) or severe cardiovascular disease (specifically symptomatic heart failure New York Heart Association Class II or greater). * Recently started psychotherapy (within 6 weeks) or planning to start such treatment during participation in the trial. * Ongoing treatment with electroconvulsive therapy (ECT), ketamine or repetitive transcranial magnetic stimulation (rTMS), except maintenance ECT, ketamine or rTMS. (Maintenance treatment is defined as the use of ECT/ketamine/rTMS for a period exceeding 3 months after a series of ECT/ketamine/rTMS treatment in order to prevent the onset of a new episode. * Other medical conditions or other concomitant drug treatment which, in the opinion of the investigators, may affect the evaluability of the trial or conditions that increase trial risk. For example, Parkinson's disease, hepatic insufficiency, ongoing cancer not in remission for more than one year, obesity surgery affecting the absorption of extended-release tablets. * Ongoing treatment with drugs that affect plasma levels of pramipexole or have similar or antagonistic mechanism of action as pramipexole are not allowed. Ongoing treatment with neuroleptics are not allowed except for low-dose quetiapine 27 (≤150 mg/day) since it has very low binding to dopamine receptors at such low doses. * Known or suspected allergy to any active substance or excipient in the medicinal product included in the trial. * Participation in other treatment studies * Other reason, as assessed by the investigator, that prevents the research subject's participation, such as the risk that the research subject is unable to complete the trial (non-compliance).