IFNG and major depressive disorder: Similarly, in cancer patients, a phenomenon of sickness behavior is expressed, such as cancer pain, CRF, cognitive and sleep disorders, depressed mood, anxiety and depression associated with high levels of pro-inflammatory cytokines expression, including IL-1β, IL-6, IL-8, TNF-α, IL-12p70, and interferon-gamma (IFN-γ) [5–8].