PPARA and major depressive disorder: Although the function of PPARα in the brain remained elusive for a long time, more and more studies indicate that PPARα is involved in physiological and pathological brain functions (e.g., in the sleep-wake cycle [191,192], depression [193,194,195,196], epilepsy [197,198,199], stroke [200,201,202,203] and schizophrenia [204]).