BDNF and Huntington disease: More recent studies, in contrast, present a more complex picture, with some studies finding no significant differences in blood-based BDNF levels across different stages of HD [88,89], and Ou et al. confirm that BDNF is not an HD biomarker as it was not associated with clinical scores or neuroimaging measures and had poor ability to discriminate mHTT carriers from healthy control or premanifest from manifest HD [89].