A functional genetic variant in the IL-6R gene known to dampen down inflammation (Ferreira et al.2013) is protective for psychosis and/or severe depression (Khandaker et al.2017b) and physical illness commonly comorbid with psychosis such as coronary heart disease (IL6R Genetics Consortium & Emerging Risk Factors Collaboration, 2012) as shown using Mendelian randomisation. This evidence concerns the gene IL6R and depressive disorder.