Background Irritability (reduced control of temper resulting in behavioural outbursts) often occurs before motor onset of Huntington’s disease (HD) and is responsible for significant impairments in quality of life and function, yet understanding of the pathophysiology is limited. Current assessments are based on diagnostic interview and self-report, but these are influenced by social context, and are unworkable in animal models. Objective tests of irritability would allow us to explore the underlying neuropsychological basis and neurobiology.
Aims Established objective protocols measuring irritable, impulsive and aggressive behaviour were selected to compare with best, current assessments in order to delineate the neuropsychological basis of irritability in HD.
Methods Participants carrying the gene expansion causing HD, from pre-symptomatic to moderately advanced stages were recruited. We compared scores on the Snaith Irritability scale and Problem Behaviours Assessment irritability sub-score with our battery. Subjects were tested on impulsivity measures (e.g. monetary temptation questionnaire) and provocation protocols (e.g. point subtraction aggression protocol).
Results Fifty-three gene positive individuals were recruited. We recorded visual analogue scales (VAS) of irritability, anger and frustration in addition to repetitive and pre-emptive button presses (motor measures). Neither the VAS scores, motor measures or impulsivity scores correlated with standard irritability assessments.
Conclusions The lack of correlation with self-report or clinician measures of irritability may reflect ineffective provocation or suggest that impulsive and irritable behaviour in HD are separate constructs, alternatively, correlation may be limited by lack of insight, drug treatment effects or impaired motor responses secondary to the motor impairments of HD.