BDNF and early-onset autosomal dominant Alzheimer disease: Differences in cerebral or peripheral concentrations of BDNF have been observed in various neurodegenerative and psychiatric disorders, such as Alzheimer's disease (Angelucci, 2009; Laske et al., 2006), major depressive disorder (Karege et al., 2002) and schizophrenia (Hashimoto et al., 2005).