This finding is supported by a study on another neurodegenerative disease, Huntington disease, in which patients with higher plasma IGF-1 levels were significantly associated with more severe cognitive decline.52 Furthermore, it is known that a decline in cognitive function occurs in patients with major affective disorders.53 Taken together, increased peripheral IGF-1 levels may represent a decrease in the central effect of IGF-1 and a decline in cognitive function in such patients. This evidence concerns the gene IGF1 and Huntington disease.