Autistic adults are markedly more prone to Parkinson’s disease, with new research showing a four-fold increase in risk compared with non-autistic peers. Swedish registry records reveal that the overlap is visible even after taking account of income, family history of psychiatric illness and known genetic susceptibility to Parkinson’s.

The investigation, led by Karolinska Institutet, analysed health data for more than two million people born in Sweden and tracked from young adulthood onwards. By focusing on diagnoses made before the age of fifty, the team could test whether autism spectrum disorder (ASD) predicts early-onset Parkinson’s rather than the more common late-life form of the condition.

One proposal is that both disorders spring from similar faults in the brain’s dopamine circuitry. Dopamine governs movement and social motivation, so defects in its signalling could conceivably underpin both the motor decline seen in Parkinson’s and the social-communication differences central to autism. “Shared biological drivers are likely,” said study author Weiyao Yin, who hopes the findings push research towards common molecular pathways.

While Parkinson’s before mid-life remains rare – even in autistic groups – the authors urge clinicians to keep an eye on neurological symptoms in autistic patients, especially those already managing multiple health issues or complex medication regimes. The project received backing from the Simons Foundation and the Swedish Research Council.