Autism spectrum disorder tied to heightened risk of Parkinson’s disease

Individuals with autism spectrum disorder face an increased risk of Parkinson’s disease (PD), independent of depression or antidepressant use and antipsychotic exposure, according to a nationwide population-based prospective cohort study.

Researchers used data from Swedish national registers and identified 2,278,565 individuals (median age at exit 34 years, 48.6 percent female) born from 1974 to 1999 with follow-up from age 20 years until 31 December 2022.

Data on autism spectrum diagnoses as a time-varying exposure were obtained from the National Patient Register. Poisson regression analysis was used to estimate the incidence of PD. Factors including preterm birth, depression, antidepressant use, and antipsychotic exposure over time were included in the analysis as potentially modifying life events.

The population contributed 33,858,476 person-years of follow-up. PD occurred at a higher rate among individuals with autism spectrum disorder than among those without (3.9 vs 1.3 cases per 100,000 person-years), yielding a rate ratio (RR) of 4.43 (95 percent confidence interval [CI], 2.92–6.72). The risk estimates remained similar after controlling for sex, socioeconomic status, family history of mental illness, family history of PD, and age at autism diagnosis.

Preterm or early-term birth showed no association with the risk of PD. Depression and antidepressant use (documented in 46.7 percent of individuals with autism) were linked to increased risk of PD (RR, 2.01, 95 percent CI, 1.40–2.88), independent of the presence of autism. On the other hand, antipsychotic exposure (documented in 31.5 percent of individuals with autism) was associated with reduced risk of PD, although it did not fully attenuate the association between autism and PD risk (RR, 2.00, 95 percent CI, 1.27–3.14) and showed no interaction effect.

The findings point to a potential shared aetiology between neurodevelopmental disorders and PD, which, in turn, underscore a need for heightened awareness of long-term neurological conditions in individuals with autism spectrum disorder.