The less frequently expressed alleles for the serotonin transporter are at increased risk for exhibiting depression given exposure to IFN-α (Bull et al., 2009; Lotrich et al., 2009), although the serotonin transporter gene interacted with alleles for IL-6 only making a difference in those who carried the allele for the less easily expressed IL-6 gene in the Bull et al. study. The gene discussed is IL6; the disease is major depressive disorder.