Background Irritability is a common neuropsychiatric symptom in patients with Huntington's disease (HD).

Aim The objective is to examine incidence, course and predictors of irritablity in subjects with HD.

Methods At baseline, irritability was measured with the Irritability Scale (IS) in 124 HD mutation carriers, together with sociodemographic, clinical, and neuropsychiatric characteristics. Follow-up evaluation was performed 2 years later on 92 (74%) subjects. Incident and persistent irritability were examined using logistic regression analysis.

Results At follow-up, 16 (18%) of the 87 subjects free of irritability at baseline had developed irritability. Of the 37 subjects with irritability at baseline, 13 (35%) no longer fulfilled the criteria of irritability, whereas 24 (65%) were still irritable. In subjects without irritability at baseline, univariate predictors of incident irritability were lower Total Functional Capacity (TFC; p=0.02), higher Unified Huntington's Disease Rating Scale total motor score (UHDRS-m; p=0.009), use of benzodiazepines (p=0.005), use of antidepressants (p=0.04), low Mini-Mental State Examination score (MMSE; p=0.03), and executive cognitive functioning scores (p=0.02) at baseline. A high UHDRS-m score remained a predictor in multivariate analysis. In subjects with irritability at baseline, univariate baseline predictors of persistent vs remitted irritability after 2 years were executive cognitive functioning (p=0.07) and use of antipsychotics (p=0.08).

Conclusion Incident irritability in HD is preceded by higher UHDRS-m scores at baseline, which corresponds with the lower TFC scores at baseline in these subjects. The majority of subjects with irritability at baseline remained irritable at follow-up, although no predictors were found.