# The structure of personality in Parkinson’s disease and the effects of age, years since diagnosis, and impulsivity

## TL;DR

This study explores how personality traits are organized in Parkinson’s disease patients and how factors like age and impulsivity affect these traits.

## Contribution

The study reveals systematic alterations in personality structure in Parkinson’s disease using a network-based approach.

## Key findings

- Personality traits like Honesty-Humility, Agreeableness, and Conscientiousness are linked to impulsive-compulsive symptoms.
- Openness splits into two clusters, one centered on the Unconventionality facet.
- Age and disease duration influence trait expression, with sex showing differences in Emotionality.

## Abstract

Parkinson’s disease (PD) is a progressive neurodegenerative disorder primarily characterized by motor and cognitive symptoms. However, emerging evidence suggests that personality alterations may also be present, potentially affecting patients’ quality of life and clinical outcomes. Prior studies have identified patterns such as lower openness and extraversion and higher neuroticism in PD patients, although findings have been inconsistent. This study aimed to investigate the structural organization of personality in PD using a network-based approach, and to examine the influence of age, sex, disease duration, and impulsive-compulsive symptoms on personality traits.

A total of 237 PD patients (aged 45–86) completed the HEXACO Adjective Scale (HAS), assessing six personality traits: Honesty-Humility (H), Emotionality (E), Extraversion (X), Agreeableness (A), Conscientiousness (C), and Openness (O). Impulsive-compulsive behaviors were assessed using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease–Rating Scale (QUIP-RS). Personality structure was analyzed via Exploratory Graph Analysis (EGA), a network model that identifies item clusters based on conditional dependencies. Multivariate multiple linear regression was used to test the effects of demographic and clinical variables on trait expression.

EGA identified seven item-level communities. Traits E, X, and C formed coherent and distinct clusters, while items from A and H tended to cluster based on item polarity (positive vs. negative wording) rather than theoretical trait boundaries. O items split into two distinct communities, one composed of the items from the Unconventionality facet, and the other encompassing the remaining O items. At the trait level, HEXACO dimensions grouped into two higher-order clusters: a Cooperativity–Integrity community (H, A, C) and an Engagement community (E, X, O). Regression analyses showed that higher ICD symptoms predicted lower levels of H, A, and C; longer disease duration was associated with lower C, and sex showed significant differences in E.

These findings reveal subtle but systematic alterations in the structural organization of personality traits in PD. Specifically, we observed a polarity-based overlap between H and A, possibly reflecting age-related convergence of the two traits—consistent with a recent study reporting similar effects in healthy aging—and a bifurcation within O centered on the Unconventionality facet, a trait often considered idiopathic in PD, even in its prodromal stages. These personality signatures may contribute to a refined clinical profiling of PD patients and support the value of incorporating personality assessment into personalized care approaches.