Background Depressed mood is common in Huntington’s disease (HD), with rates of between 33% and 69% in mutation carriers. Depressed mood is a major predictor of suicidal ideation, and is associated with significant impairments of quality of life and function. Despite this, little is understood regarding the neurobiology and cognitive processes underlying low mood and suicidal ideation in HD.

Aims This study used a battery of neuropsychological tasks, that measure cognitive processes shown to be involved in major depressive disorder in the general population, and compared task performance with gold standard measures of mood and suicidal ideation in HD.

Methods 53 gene positive HD patients and 26 healthy controls completed gold standard measures of mood in HD (Problem behaviours Assessment short form {PBAs}, Hospital Anxiety and Depression Scale{HADS}, Mini International Neuropsychiatric Interview{MINI}) in addition to a task battery encompassing a novel measure of depressive cognition (estimation of one’s own performance); measures of reward and effort (progressive ratio task, rewarded reaction time task); executive function measures (verbal fluency and extra-dimensional set shifting task); and a self report questionnaire of reward value.

Results Patients had higher HADS scores and lower premorbid IQ than controls, no other demographic group differences were found. Group differences were seen on the executive function measures, reward value measure and depressive cognition task. Lower executive function and lower depressive cognition scores predicted suicidal ideation, but none of the other gold standard mood measures were associated with task performance.

Discussion Suicidal ideation in Huntington’s disease is associated with impaired executive function and over-estimate of performance on a task of depressive cognition. Over-estimate of performance may relate to mania, which has been linked with suicidality in bipolar disorder.