Higher rates of depression are seen prior to genetic testing in gene carriers compared with gene negative individuals at risk for Huntington’s disease,17,25 whilst depression-like behaviour has been found in animal models of Huntington’s disease26 that can be rescued with inactivation of the Huntingtin mutation.27 Such findings suggest that depression is an integral part of the pathology of Huntington’s disease. This evidence concerns the gene HTT and major depressive disorder.