BDNF and major depressive disorder: Experimental models of adolescent and adult ethanol exposure demonstrate that repeated alcohol administration decreases BDNF expression and signalling in the hippocampus, prefrontal cortex and amygdala, which is associated with impaired neurogenesis, dendritic spine loss and increased anxiety- and depression-like behaviour; pharmacological or genetic restoration of BDNF signalling can attenuate alcohol intake and partially rescue these structural and behavioural deficits [86,87].