IFN-α significantly increased depression severity ratings, as well as subjective ratings of state anxiety and fatigue by 6–8 weeks, which is in keeping with numerous previous reports of induction of depressive symptoms by this treatment (Musselman et al.2001; Hauser et al.2002; Schaefer et al.2002; Capuron & Miller, 2004; Maddock et al.2005; Fontana et al.2008). This evidence concerns the gene IFNA1 and major depressive disorder.