A large-scale Swedish study has found that individuals diagnosed with Autism Spectrum Disorder (ASD) may face a significantly heightened risk of developing Parkinson’s disease earlier in life. Conducted by researchers at the Karolinska Institutet and published in JAMA Neurology, the study analysed registry data from over two million people born in Sweden between 1974 and 1999. Participants were followed from the age of 20 until the end of 2022, enabling the researchers to assess long-term health outcomes, including the potential emergence of early-onset Parkinson’s disease—a neurodegenerative condition known primarily for its impact on movement and motor control.
The investigation sought to explore a possible link between autism and early-onset Parkinson’s, which occurs before the age of 50. Autism, a neurodevelopmental condition affecting communication, social interaction, and behaviour, has not traditionally been associated with Parkinson’s, a disease involving the degeneration of dopamine-producing neurons in the brain. However, this new research found that people with autism were approximately four times more likely to develop Parkinson’s disease than those without an autism diagnosis. Importantly, this increased risk persisted even after adjusting for a range of potential confounding factors, including socioeconomic status, family history of mental illness or Parkinson’s, and other health variables.
Dr Weiyao Yin, the study’s lead author and a researcher at Karolinska’s Department of Medical Epidemiology and Biostatistics, suggested that shared biological mechanisms might underlie both conditions. One leading hypothesis is the involvement of the brain’s dopamine system—a neurotransmitter pathway crucial for both motion control and social behaviour. Since the loss of dopamine-producing neurons characterises Parkinson’s, and prior research has hinted at dopamine dysregulation in autism, the authors propose that the two disorders may be linked through this shared neural substrate. However, Dr Yin cautioned that while the findings are compelling, more research is necessary to clarify the precise mechanisms involved.
The study also took into account the high prevalence of psychiatric conditions such as depression in individuals with autism, many of whom are prescribed antidepressants or antipsychotics. Some of these medications are known to cause Parkinsonian symptoms, potentially confounding the association between autism and Parkinson’s disease. When the researchers adjusted for the use of these drugs, the strength of the association weakened somewhat, but individuals with autism still had double the risk of developing Parkinson’s. This suggests that while psychiatric medication use may contribute to the observed risk, it is unlikely to explain it thoroughly, and underlying biological pathways may still be at play.
Despite the statistically significant findings, the researchers note that early-onset Parkinson’s disease remains rare in the general population and even among people with autism. Moreover, the study cohort had a mean age of just 34 at the end of the follow-up period, meaning that many participants had not yet reached the age at which Parkinson’s is typically diagnosed. As such, the long-term risk trajectory for this population remains uncertain. Future studies will be essential to determine whether the elevated risk continues into older adulthood, where Parkinson’s becomes more prevalent.
The study concludes with a call for greater awareness and continued monitoring of individuals with autism as they age. Dr Sven Sandin, the study’s senior author and a statistician at Karolinska Institutet, emphasised the need for long-term healthcare planning. “This is a vulnerable group,” he said, “with high co-morbidity and significant use of psychotropic medications. Clinicians should be aware of these risks and ensure regular follow-up.” While the research does not suggest imminent concern for most individuals with ASD, it opens an essential line of inquiry into how neurodevelopmental and neurodegenerative disorders might intersect throughout a lifetime.
More information: Weiyao Yin et al, Risk of Parkinson Disease in Individuals With Autism Spectrum Disorder, JAMA Neurology. DOI: 10.1001/jamaneurol.2025.1284
Journal information: JAMA Neurology Provided by Karolinska Institutet
