The present results are interesting in light of a study in human post-mortem brain tissue of ~12,000 ranked genes according to robustness of circadian rhythmicity across six brain regions; the top ranked circadian genes in that study were ARNTL, PER2, PER3 and NR1D1 and dysregulation in MDD vs controls were observed in these genes22. This evidence concerns the gene PER3 and major depressive disorder.