A commonly used drug for Parkinson’s disease (PD) called Mirapex (pramipexole) appears to also have antidepressant effects, according to a study published in The Lancet and reported by Medscape Today.

PD is a central nervous system disease characterized by the loss of motor control over time. It typically strikes people as they get older, but it can have an earlier onset, as has been the case in the actor Michael J. Fox. One of the key features of PD is the brain’s loss of ability to produce and use the neurotransmitter dopamine. Among other things, dopamine helps the brain control our movement and it provides feelings of euphoria. Thus, a number of treatments for PD—including Mirapex—work by stimulating dopamine receptors.

Now a study by Paolo Barone, MD, PhD, and his colleagues from the University of Naples in Italy reveals that the drug might also reduce the symptoms of depression in people with PD who are depressed. Moreover, the effect appears to be independent of an improvement in PD symptoms.

Because improvements in PD motor symptoms often alleviate depressive symptoms, “it’s difficult to show whether improvement of depressive symptoms with a dopaminergic agent is secondary to improvement of motor symptoms,” Barone said. “The tricky point in this study was to disentangle motor from depressive improvement.”

Barone’s team “disentangled” the two disorders by primarily focusing on people whose PD symptoms were stable. This allowed the researchers to more clearly measure improvements in depressive symptoms, which they did. Barone and his colleagues found that Mirapex led to modest, but clinically significant, improvements in depressive symptoms in the 287 people they studied.

“Parkinson’s disease patients are already on polytherapy, and if we can treat depressive symptoms with an agent that is also able to treat dopaminergic symptoms, we can get two effects from one pill,” Barone said. “The message for doctors is that before treating your patients with antidepressants, try to optimize antiparkinsonian treatment, including [Mirapex].”