GAD2 and depressive disorder: Disrupted GABA signaling and GABA deficit is also hypothesized to play a role in the development of depression and anxiety (Luscher et al., 2011), while Gad2 mRNA, the synthesis enzyme of GABA, was upregulated after chronic treatment with the serotonin and noradrenaline reuptake inhibitor venlafaxine (Tamasi et al., 2015).