Impulse control disorders in Parkinson's disease: the role of personality and cognitive status

This study reviews empirical findings on two debated issues related to the phenomenon of impulse control disorders (ICD) in patients with Parkinson's disease (PD) treated with dopamine agonists: the role of "premorbid" or "baseline" personality traits and the role of cognitive status. A review of both these issues may help clinicians to understand why only some PD patients, when treated with dopamine agonists, develop an ICD: besides the treatment, which other neuropsychiatric characteristics represent a risk factor to develop an ICD? A literature review was performed on studies of ICD in PD patients, in electronic databases ISI Web of Knowledge, Medline and PsychInfo, conducted in January 2011. In the general population, impulsivity, depression and difficulties with executive functions, especially of inhibitory control, are factors associated with ICD development. As regards cognitive functions, PD patients present executive difficulties, and patients with ICD present more difficulties in comparison to patients without ICD. As regards personality characteristics, PD patients present a trait of negative affect, which could predispose them to affective disorders and could represent an affective risk factor for the development of ICD; as regards impulsivity, preliminary findings support the hypothesis that premorbid "baseline" levels may moderate the decrease of impulsivity because of the progressive dopaminergic deficit in PD patients and therefore also moderate the development of ICD. Longitudinal psychometric and cognitive studies, following PD patients since the clinical diagnosis and during dopaminergic treatment, are needed to confirm the role of personality traits and cognitive status on ICD development in this clinical population.