Many studies have shown a close link between C9orf72 expansion carriers and the presence of neuropsychiatric symptoms, both early on as a presenting feature and during the course of the disease.25–28 Moreover, C9orf72 mutations are the most common genetic cause of ALS,29 30 with previous studies showing an association of ALS with early neuropsychiatric disturbances independent of other behavioural symptoms.31 Here, C9orf72 is linked to amyotrophic lateral sclerosis.