Altered expression of melatonin receptors or clock genes has been frequently reported in neurodegenerative diseases and psychiatric disorders, including Alzheimer’s disease (AD) (Wu et al., 2007; Cronin et al., 2017), Parkinson’s disease (PD) (Adi et al., 2010; Li et al., 2017), and Huntington’s disease (HD) (Pallier et al., 2007; van Wamelen et al., 2013). The gene discussed is CLOCK; the disease is Alzheimer disease.