Background Psychiatric symptoms are more prevalent in Huntington’s disease (HD) than in the general population; however, the reasons for this overrepresentation are unknown. Previous small-scale studies demonstrating clustering of particular psychiatric phenotypes in some HD families suggest that familial (genetic and/or environmental) factors may play a role.

Aim To determine whether psychiatric syndromes and symptoms aggregate in families affected with HD by conducting a systematic, standardised assessment in a large sample of sibling pairs with HD.

Method Fifty-three sibling pairs (86 individuals from 40 families) who were all gene positive for HD underwent a lifetime psychiatric history assessment using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) and a modified version of the Problem Behaviours Assessment for Huntington’s disease (PBA-HD).

Results Moderate and significant within-pair associations were found for: i) lifetime DSM-IV diagnosis of any depressive disorder (n = 50, κ=0.444, p = 0.002); ii) lifetime severity of depression (the depression sub-scale score of the Bipolar Affective Disorder Dimensional Scale) (n = 50, ICC=0.36, p = 0.005); and, iii) lifetime history of aggression and irritability (n = 52, κ=0.418, p = 0.003; n = 52, κ=0.341, p = 0.013 respectively).

Conclusion The clustering of depressive disorder, irritability and aggression in some HD families indicates the importance of familial factors (perhaps biological) in the aetiology of these psychiatric syndromes/symptoms in HD.