GSTM1 and depressive disorder: Kawano (Kawano et al., 2016; Takamiya et al., 2017) investigated the relationship between oxy-Hb integral values and the severity of depression, as assessed using the Hamilton Depression Scale in patients with various psychiatric disorders, such as MDD, and found that the severity of depression was negatively correlated with the integral value in the frontal lobe, irrespective of psychiatric disorders.