CLOCK and mood disorder: Mutations in core regulatory clock genes are associated with both sleep and mood disorders, suggesting that molecular mechanisms affecting sleep and mood are influenced, in part, by the circadian clock (Randler, 2008; Mendlewicz, 2009; Soria et al., 2010; Lee et al., 2011; Courtet and Olié, 2012; McCarthy and Welsh, 2012; McClung, 2013; Robillard et al., 2013; Sivertsen et al., 2015; Antypa et al., 2016) and may utilize similar downstream pathways.