On the other hand, skin fibroblasts isolated from patients with chronic schizophrenia lose rhythms in the expression of the clock genes CRY1 and PER2 when compared with healthy controls (Johansson et al., 2016), and PER1/2/3 and NPAS2 mRNA levels were reported to be altered in white blood cells from schizophrenia patients (Sun et al., 2016). Here, PER2 is linked to schizophrenia.