From pre‐clinical studies, L‐Dopa administration once daily at 15:00 for 21 consecutive days in an animal model of PD (6‐OHDA‐treated rats) improves motor deficiencies but also leads to phase delays and a lower amplitude in the expression of clock genes in the SCN and striatum whilst also eliminating the rhythm of striatal dopamine and increasing the average amount of dopamine in the striatum (Li et al., 2017). The gene discussed is CLOCK; the disease is Parkinson disease.