SST and major depressive disorder: Altered diurnal rhythms of the anxiolytic neurotransmitter somatostatin were also reported in the amygdala of subjects with BD (Pantazopoulos et al., 2016), with decreased levels of somatostatin occurring in the morning, coinciding with reported increased severity of anxiety and depression (Murray et al., 2002; Murray, 2007, 2008; Wirz-Justice, 2008).