C9orf72 and psychiatric disorder: Additionally, the lower odds of association between the C9orf72 expansion and psychiatric diseases found in our population, although apparently unexpected, may be explained on the basis of previous literature referring that behavioral abnormalities, rather than psychosis or other psychiatric syndromes per se, within clinical profile of FTD, were frequently observed among C9orf72 expansion carriers (Watson et al., 2016; Devenney et al., 2017; Ducharme et al., 2017).