Furthermore, this information is supported by studies showing an extensive population and individual variation in this ability involving both genetic (increased or decreased P450 activity, decreased reduced glutathione [GSH]) and environmental (drugs or chemicals such as smoking inducing P450, cirrhosis and drugs inhibiting P450, decreased GSH such as in AIDS, deficiency of antioxidants such as Vitamin E, C, selenium) [24]. The gene discussed is CYP2B6; the disease is Cirrhosis.