Neuroticism May be Parkinson’s Risk Factor

The personality trait neuroticism correlates with a higher risk of developing Parkinson’s disease, according to recent research.

The study, “Neuroticism and Risk of Parkinson’s Disease: A Meta-Analysis,” was published in the journal Movement Disorders.

Neuroticism refers to an individual’s tendency to experience negative emotions, self-consciousness, vulnerability to stress, and an inability to resist urges. It attracts some attention as a personality trait for its association with a higher risk of several poor health outcomes, including Alzheimer’s disease and related dementias.

Its relationship to Parkinson’s is less-understood.

“Some clinicians think that the anxiety and depression is just the result of Parkinson’s,” Antonio Terracciano, PhD, the study’s lead author, said in a Florida State University press release.

“However,” he added, “our findings suggest that some emotional vulnerability is present early in life, years before the development of Parkinson’s disease.”

Terracciano and his colleagues explored patient data from the UK Biobank, a database of genetic and health information from approximately a half-million individuals. They also integrated findings from past research that looked at neuroticism and Parkinson’s.

Of 491,653 Biobank participants who completed a neuroticism questionnaire, 898 had Parkinson’s. Over nearly 12 years (11.91) of follow-up, 1,142 individuals were diagnosed with Parkinson’s.

Those with Parkinson’s at the time of completing the survey (baseline) scored higher in terms of neuroticism than those without a diagnosis. Respondents who were not diagnosed with Parkinson’s at baseline, but developed it during the follow-up period had the highest neuroticism scores, compared to both participants with Parkinson’s at baseline and those without the disorder.

Overall, the risk of developing Parkinson’s increased by more than 80% among those who scored in the top quartile in the neuroticism score.

The observed effect did not vary according to sex or socioeconomic status, and neuroticism remained significantly associated with Parkinson’s risk after accounting for smoking, physical activity, anxiety, and depression.

The researchers identified three published studies that also reported associations between neuroticism and Parkinson’s risk. Including these studies brought the total number of participants to 548,284, with 1,670 Parkinson’s cases occurring over the course of the studies.

All studies showed the same association between neuroticism and Parkinson’s, which Terracciano called a “pretty robust and replicable” finding.

“It kind of gives you a better understanding of the risk factors for the disease and what could be a contributing cause,” he said. “This is one of many [factors], but the evidence is convincing.”

The investigators cautioned that rather than a risk factor, there is a chance that neuroticism is an early symptom of the disorder, occurring in the period between the first appearance of symptoms and full Parkinson’s development.

Although this topic needs more research, the team still favors the hypothesis that neuroticism is a risk factor, more than an early symptom. The finding that the Biobank participants who developed Parkinson’s later scored higher for neuroticism than those with Parkinson’s at baseline, the researchers say, supports this idea.

“It is worth noting,” they wrote, “that the largest genome-wide association study of neuroticism found top hits in the microtubule-associated protein tau gene, which is also implicated in [Parkinson’s].”

Overall, the team concluded that their results from the UK Biobank and analysis of other studies “indicate that neuroticism is consistently associated with a higher risk of incident [Parkinson’s].”