Autism linked to elevated risk of Parkinson’s disease, Swedish study finds  

Individuals diagnosed with autism may face a significantly increased risk of developing early-onset Parkinson’s disease, according to a large-scale study from Karolinska Institutet. The findings suggest that autism spectrum disorder (ASD) and Parkinson’s disease may share common underlying biological mechanisms.

The study analysed registry data from more than two million individuals born in Sweden between 1974 and 1999. Participants were followed from the age of 20 until the end of 2022. The researchers examined potential links between ASD – a neurodevelopmental condition affecting cognition, behaviour and social interaction – and Parkinson’s disease diagnosed before the age of 50, which primarily affects motor function.

The results showed that individuals with an autism diagnosis were approximately four times more likely to develop early-onset Parkinson’s disease compared with those without such a diagnosis. This association remained statistically significant after adjusting for confounding factors, including socioeconomic status, genetic predisposition to psychiatric or neurological conditions and other relevant variables.

“This indicates that there can be shared biological drivers behind ASD and Parkinson’s disease…” 

…said Dr Weiyao Yin, first author of the study and researcher at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.

“One hypothesis is that the brain’s dopamine system is affected in both cases, since the neurotransmitter dopamine plays an important part in social behaviour and motion control,” they said.

It is well established that dopamine-producing neurons deteriorate in Parkinson’s disease. Previous studies have also suggested that dopamine may play a role in autism, although further research is needed to confirm this link.

“We hope that our results will eventually help to bring greater clarity to the underlying causes of both ASD and Parkinson’s disease,” Dr Yin added.

The study also accounted for common co-morbidities and treatments. Depression, use of antidepressants and antipsychotic medication – which may induce Parkinson’s-like symptoms – are prevalent among individuals with autism. When these factors were considered, the association between ASD and Parkinson’s disease was reduced, though the risk remained approximately twice as high compared with those without ASD.

The researchers emphasised that their analysis was limited to early-onset Parkinson’s disease. By the end of the study, the average participant age was 34, and the overall incidence of Parkinson’s disease remained low. Further studies will be required to assess whether the elevated risk continues into older age.

“The healthcare services need to keep people with ASD – a vulnerable group with high co-morbidity and a high use of psychotropics – under long-term observation,” said Professor Sven Sandin, senior author of the study and a statistician and epidemiologist at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.

“At the same time, it is important to remember that a Parkinson’s diagnosis before the age of 50 is very rare, including among people with autism.”

For further reading please visit: 10.1001/jamaneurol.2025.1284