CLOCK and anxiety disorder: Single nucleotide polymorphisms in core circadian clock genes have been associated with autism spectrum disorders (Nicholas et al., 2007); attention deficit hyperactivity disorder (Kissling et al., 2008; Xu et al., 2010), major depressive disorder (Partonen et al., 2007; Lavebratt et al., 2010; Soria et al., 2010), bipolar disorder (Nievergelt et al., 2006; Shi et al., 2008; Soria et al., 2010), anxiety disorders (Sipila et al., 2010) and substance abuse disorders (Kovanen et al., 2010; Dong et al., 2011; Wang et al., 2012).