Cryptochrome circadian regulator (CRY) 2 is one of these circadian clock genes involved in cell-cycle progression and DNA-damage checkpoint control.22 Psychiatric disorders are frequently associated with deregulation of circadian rhythm responses, such as cortisol secretion and sleep, and affective symptoms can be exacerbated by disruption of circadian rhythms.23 For example, one study reported that patients with BD have lower CRY2 expression when compared to controls24 and CRY2 has been associated with MDD and SZ25–27 and also with rapid cycling in BD.28 This evidence concerns the gene CRY2 and major depressive disorder.