Individuals with autism spectrum disorder (ASD) may face a significantly higher risk of developing Parkinson’s disease (PD) later in life, according to a new study published online on May 27 in JAMA Neurology.

The large-scale, population-based cohort study was led by Dr. Weiyao Yin and a team of researchers from the Karolinska Institutet in Stockholm, Sweden. Drawing from Swedish national health registers, the study analyzed data from more than 2.2 million individuals, accounting for nearly 34 million person-years.

The findings revealed that Parkinson’s disease occurred in 24 out of 51,954 individuals diagnosed with ASD — a rate of 3.9 cases per 100,000 person-years — compared to 438 cases among over 2.2 million individuals without ASD, or 1.3 cases per 100,000 person-years. This translated to a relative risk of 4.43, meaning individuals with autism were more than four times as likely to develop Parkinson’s as those without the condition.

Importantly, the elevated risk persisted even after adjusting for potential confounding factors, including sex, socioeconomic status, family history of psychiatric illness or Parkinson’s disease, and age at ASD diagnosis.

The study also found that while depression and the use of antidepressants independently increased the risk of PD (relative risk 2.01), and antipsychotic exposure had a similar effect (relative risk 2.00), these factors did not fully explain the observed association between autism and Parkinson’s. Furthermore, birth factors such as preterm or early-term delivery showed no correlation with Parkinson’s risk and did not alter the ASD-PD association.

“ASD was associated with increased risk of PD, even after adjusting for depression, antidepressant use, and antipsychotic exposure,” the researchers noted. “These findings suggest a potential shared etiology between neurodevelopmental disorders and PD.”

The study adds to growing scientific interest in the long-term neurological health of individuals with autism and raises important questions about shared biological pathways that may underlie both neurodevelopmental and neurodegenerative disorders.