VDR and major depressive disorder: The observed association between VDR polymorphisms and quality of life is of importance to daily clinical practice because patients with AIH struggle with serious symptoms that significantly affect their well-being, including mood disturbance, cognitive dysfunction, chronic fatigue, decreased physical activity, and a high rate of previously unrecognized severe symptoms of depression and anxiety [7,50]; thus, the presence of the CC ApaI variant may result in those symptoms worsening.