Another new study has found a connection between mental illness (depression or psychosis) and the immune system. The study, done at the University of Cambridge, and published in JAMA Psychiatry, is the first longitudinal study (it followed a group of people from age 9 to age 18) looking at the link between an immune molecule called interleukin-6 (IL-6) and it's relationship to mental illness. The authors found that higher IL-6 levels were correlated to depression and/or psychosis. Higher IL-6 levels are correlated with increased levels of infection in the body.
From the article in Science Daily (August 13, 2014):
Dr Golam Khandaker from the Department of Psychiatry at the University of Cambridge, who led the study, says: "Our immune system acts like a thermostat, turned down low most of the time, but cranked up when we have an infection. In some people, the thermostat is always set slightly higher, behaving as if they have a persistent low level infection -- these people appear to be at a higher risk of developing depression and psychosis..."
They don't name specifics, but I've already blogged about low-level chronic strep, herpes, h. pylori, and other microbes. So it seems that keeping the immune system healthy may be an important way to potentially address mental illness.