Further to this, it has also been shown that cytokine immunotherapy in the form of IL-2 and IFN-α for the treatment of hepatitis C (Hep C) and certain types of cancer, such as malignant melanoma, can induce depression in 30% to 50% of these patients who are otherwise psychiatrically normal (Capuron et al., 2000; Bonaccorso et al., 2001; Capuron et al., 2001). The gene discussed is IL2; the disease is major depressive disorder.