Autism linked to elevated risk of Parkinson’s disease

People with an autism diagnosis are at a higher risk of developing Parkinson’s disease early in life, a large-scale study from Karolinska Institutet published in JAMA Neurology reports. The researchers believe that the two conditions can share underlying biological mechanisms.

The study is based on registry data from over two million people born in Sweden between 1974 and 1999, who were followed from the age of 20 up to the end of 2022.

The researchers questioned a possible connection between the neuropsychiatric diagnosis Autism Spectrum Disorder (ASD), which affects an individual’s thought processes, behavior and interpersonal communication, and early-onset Parkinson’s disease, a condition that affects locomotion and movement.

Dopamine can be involved

The results show that people with an autism diagnosis were four times more likely to develop Parkinson’s disease than people without such a diagnosis, a correlation that remained when controlling for socioeconomic status, a genetic predisposition for mental illness or Parkinson’s disease and other such factors.

“This indicates that there can be shared biological drivers behind ASD and Parkinson’s disease,” says the study’s first author, Weiyao Yin, 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 behavior and motion control.”

It is well-known that dopamine-producing neurons are degraded in Parkinson’s disease. Previous studies have also shown that dopamine is possibly implicated in autism, but more research needs to be done to confirm this.

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

Medical checkups are vital

Depression and the use of antidepressants are common in people with autism, as are antipsychotic drugs, which are known for being able to cause Parkinson’s-like symptoms. When the researchers adjusted for these factors, the correlation between ASD and the later development of Parkinson’s disease was less salient, but the risk was still double.

The researchers point out that they only analyzed early-onset Parkinson’s disease before the age of 50 and that the average age of participants by the end of the study was 34. The incidence of Parkinson’s disease was therefore very low. Future studies will need to examine if the elevated risk persists into older age.

“The health care services need to keep people with ASD—a vulnerable group with high co-morbidity and a high use of psychotropics—under long-term observation,” says the study’s last author, Sven Sandin, statistician and epidemiologist at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet.

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

In Parkinson’s, dementia may occur less often, or later, than previously thought