Problem Behavior

First, existing screening and diagnostic instruments for ICDs and other compulsive behaviors that have been used in PD and the general population were reviewed(1 ;6 (link);19 (link);21 (link)–23 (link)). Second, input was solicited from outside experts in the area of ICDs in PD (MNP, JM, and VV) and from an expert in questionnaire development (JAS). Third, a preliminary ICD section of the QUIP was structured to be consistent with diagnostic criteria or defining clinical characteristics as described in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR)(1 ). This consisted of an introductory question and four additional questions that addressed cognitive symptoms, affective symptoms, lack of ability to reduce or stop the behaviors, and activities that enable continuation of the behaviors. The compulsive medication use section was modeled on both Giovannoni’s proposed criteria for hedonistic homeostatic dysregulation and DSM-IV substance dependence criteria. While minor wording changes were made in subsequent drafts, the structure of these sections remained consistent throughout the instrument development process. The other compulsive behaviors section was designed with conciseness in mind (an introductory question for each of the three behaviors plus two common additional questions). Guiding principles in the design of the QUIP included making it self-administered, brief yet comprehensive, and consistent in wording across different ICDs and other compulsive behaviors.
Next, the preliminary QUIP was administered to a sample of healthy controls (10 research staff members who work with neurodegenerative disease and psychiatric populations), and modifications were made based on the feedback received. Finally, the QUIP was administered to five PD patients and their informed others, and additional modifications were made based on the feedback received from them.
The final version that was validated queried about behaviors that occurred at any time since the onset of PD (either inactive or active) that lasted at least four weeks. We chose the time frame of “anytime during PD” due to the observation that a substantial number of PD patients who have experienced an ICD during PD are currently asymptomatic due to clinical management, but may be at elevated risk of developing an ICD in the future. Another version of the QUIP that queries only about active behaviors is also available; it is identical to the validated version except for the time frame queried. The final version of the QUIP is divided into three sections: (1) five questions (including an introductory question that defines and gives examples of problem behaviors) for the four ICDs reported in PD; (2) three distinct introductory questions and two common additional questions for hobbyism, punding, and walkabout; and (3) five questions (including an introductory question) for compulsive medication use. The Flesch-Kincaid Readability Test assessed the QUIP to require a 12^th grade reading level.

In this study, we used the parent-rated, English (United States) and Spanish versions of the SDQ (Goodman & Scott, 1999 (link); www.sdqinfo.org). The SDQ has been widely used and has been normed for the United States (Bourden et al., 2005 (link)). The SDQ consists of five subscales: Emotional Symptoms, Conduct Problems, Hyperactivity/Inattention, Peer Problems, and Prosocial Behavior. Each subscale has five items and each item is stated as a strength or weakness but not both. The number stated as weaknesses varies across these subscales. For Emotional Symptoms, all five are stated as weaknesses; for Conduct Problems, four of the five; for Hyperactivity/Inattention, three of the five; for Peer Problems, two of the five; and for Prosocial, none of the five (i.e., all are stated as strengths). The score on each subscale of the SDQ is determined by the summation of items stated as strengths and weaknesses. Weaknesses are scored 0 for “not true,” 1 for “somewhat true,” and 2 for “certainly true.” Reverse scoring is used for strengths, which are scored 2 for “not true,” 1 for “somewhat true,” and 0 for “certainly true.”
The SDQ Hyperactivity-Inattention subscale provides a rating reflecting the symptom domains of ADHD (i.e., inattention, hyperactivity, and impulsivity). It consists of three items stated as difficulties (1 = restless, overactive, cannot stay still for long; 2 = constantly fidgeting or squirming; and 3 = easily distracted, concentration wanders) and two items as strengths (4 = thinks things out before acting and 5 = sees tasks through to the end, good attention span).
As directed by the SDQ manual, the items stated as difficulties were scored to reflect the degree of psychopathology (0 = not true, 1 = somewhat true, and 2 = certainly true). The items stated as strengths were reverse scored (2 = not true, 1 = somewhat true, and 0 = certainly true). Thus, the minimum on each subscale is 0 (representing lack of psychopathology) and the maximum score on each subscale is 10 (representing presence of psychopathology, except in the case of the Prosocial Behavior subscale).