Influence of personality on the relationship between gray matter volume and neuropsychiatric symptoms in multiple sclerosis

OBJECTIVE: Research has revealed an association between personality traits and health outcomes, and in multiple sclerosis (MS), there are preliminary data showing a correlation between personality traits and brain volume. We examined the general hypothesis that personality influences the relationship between gray matter volume (GMV) and cognitive/neuropsychiatric MS features. METHODS: Participants were 98 patients with MS who underwent magnetic resonance imaging and were tested with the Symbol Digit Modalities Test and the Neuropsychiatric Inventory, the latter providing measures of depression and euphoria that can be characteristic of MS, that is, cheerful indifference and disinhibition. Personality traits were assessed with the NEO Five Factor Inventory. We examined the correlation between personality traits and both GMV and symptoms, and then modeled mediation and moderation influences on the relationships between GMV and cognitive/neuropsychiatric features. RESULTS: Linear regression modeling revealed that GMV (r = 0.54, p <.001) and NEO Five Factor Inventory low conscientiousness (r = 0.36, p = .001) were associated with cognitive function, but no mediator or moderator effects were observed. However, conscientiousness mediated the relationship between GMV and symptoms of euphoria (p = .002). The moderator analysis revealed a significant influence of high neuroticism on the GMV-euphoria relationship (p = .029). CONCLUSIONS: Low conscientiousness and high neuroticism are associated with neuropsychiatric complications in MS, and each influences the relationship between GMV and euphoria. The findings suggest that patients with low conscientiousness are at higher risk for MS-associated cognitive dysfunction and neuropsychiatric symptoms, a conclusion that has implications for the emerging role of personality in clinical neuroscience.