Re-examining the Parkinsonian Personality hypothesis: A systematic review

The main objective of neurological examination for Parkinson's disease (PD) is to discover premorbid signs of the neurodegenerative disease. This is based on the definition of subclinical motor and non-motor symptoms, while psychological features are frequently neglected. However, the idea of premorbid "parkinsonian" personality (PP) has been discussed for over a century in clinical writings. Here, thirty-one articles have been included in this qualitative synthesis of literature aimed at re-examining this question. Early retrospective studies described personality profile using framed psychoanalytic terms such as negative emotionality, emotive rigidity and depression. Nowadays, the employment of standardized taxonomies of personality allows defining PP in a more unified framework. However, this large amount of evidence could not unravel the premorbid nature of PP. Four recent long-term prospective works have provided new impetus to this field of study demonstrating that low novelty seeking, high introversion, neuroticism and harm avoidance precede PD onset and might be a risk factor. Moreover, some PP dimensions (novelty seeking) change dynamically over time as a function of dopaminergic treatment or dysfunctions. The reviewed literature demonstrates that personality profile is an important hallmark of clinical course of PD, which should be used to assess subjects' vulnerability into daily clinical practice.