On Dec. 23, 2024, a study from Radboud University reported that the standard medication levodopa does not always work against tremors in Parkinson’s disease, especially in stressful situations. Propranolol, however, does work during stress, providing insight into the role of the stress system in tremors. MRI scans reveal that propranolol directly inhibits activity in the brain circuit that controls tremors. Doctors may consider this medication when levodopa is ineffective.

The medication in question, propranolol, is a beta-blocker that inhibits the action of stress hormones. It was developed for high blood pressure and heart arrhythmias, has been around for a long time, and is already used as a standard treatment for essential tremor—a condition in which people experience tremors without other neurological symptoms. There were already indications that propranolol might reduce tremors in Parkinson’s, but until now, no thorough research has explored its potential effects.

The study showed that propranolol reduced tremors both at rest and during stress. The MRI scans revealed how this works: after taking the medication, the brain circuit responsible for tremors showed less activity. The research was published in Annals of Neurology.