Jumping to conclusions bias, psychosis and impulsivity in early stages of Parkinson’s disease

Objectives The aim was to explore the correlations between Jumping to Conclusions (JtC) tendency and neuropsychiatric features in patients with early Parkinson’s disease (PD). Background According to few reports, PD patients with impulsive–compulsive behaviors (ICBs) are prone to working memory difficulties including JtC bias. The correlation of psychotic features and JtC tendency remains still unclear. Methods Healthy controls and patients within 3 years of PD onset were recruited. Participants were examined for psychotic symptoms using a 10 question PD-specific psychosis severity scale. JtC was measured by a probalistic reasoning scenario (beads task). In PD group, medication use, motor and non-motor symptoms were documented. Impulsivity was evaluated using the Questionnaire for Impulsive–Compulsive Disorders in PD (QUIP). Results The prevalence of JtC bias was 9% (6/70) in healthy individuals, compared to 32% (22/68) of PD group [ p = 0.001]. No association was detected between the presence of JtC tendency and PD-associated psychosis ( p = 0.216). Patients with JtC had shorter duration of PD, more tremor-dominant PD subtype and higher QUIP scores, regardless of the dopaminergic therapy ( p = 0.043, p = 0.015, p = 0.007, respectively). A trend towards attention and inhibition control deficit was noticed in JtC patients. Conclusions We found a high prevalence of JtC bias in early, cognitively intact PD population and a potential link between subthreshold ICBs and poor performance on beads task. Additional studies are needed to confirm our results and elaborate on the mechanisms that correlate impulsivity with JtC tendency, which are likely to be different from those mediating psychotic features in early PD.