Development and initial psychometric evaluation of a multidimensional neuropsychiatric screening questionnaire for Parkinsons Disease (PD-NPSQ)

Neuropsychiatric syndromes are highly prevalent in Parkinson's disease (PD) and represent a major determinant of reduced quality of life, increased caregiver burden, and adverse clinical outcomes. Common syndromes include depression, anxiety, apathy, impulse control disorders, fatigue, psychosis, and, less frequently, manic manifestations. Despite their clinical relevance, these syndromes are often underrecognized in routine care, partly due to fragmented assessment strategies that rely on multiple domain-specific instruments. The aim of the study presented in this thesis is to describe the development and initial evaluation of a brief, multidimensional screening questionnaire for the efficient assessment of neuropsychiatric syndromes in patients with PD, in order to save time and not exhaust the patient with multiple questionnaires. Particular emphasis is placed on its applicability to patients undergoing Deep Brain Stimulation (DBS) treatment, in which neuropsychiatric complications may arise both pre- and postoperatively and require systematic monitoring. The screening tool was developed based on a comprehensive literature review, and on a factor analysis and item reduction of relevant items from validated questionnaires. It was designed to be concise, clinically feasible, and sensitive across multiple neuropsychiatric domains. The resulting initial version was administered to a clinical sample of patients with PD as well as a healthy control group. Based on the findings from this initial evaluation, the questionnaire was revised into the Parkinson's Disease Neuropsychiatric Syndromes Questionnaire (PD-NPSQ). Psychometric evaluation of the initial version included analyses of internal consistency, convergent validity through comparison with established measures, as well as the dimensional structure of each subscale. Once fully validated, such a tool has the potential to improve early detection, support clinical decision-making, and enhance patient management, particularly in patients undergoing DBS.