Depression is a result of inflammation caused by the body's immune system, according to psychologists at the University of California in Los Angeles. Researchers found that a family of proteins called cytokines sets off inflammation in the body, and switches the brain into sickness mode.
During the study it was seen that both cytokines and inflammation flare up during depressive episodes and these levels drop off during the remission period in people with bipolar disorder. Healthy people can also be temporarily put into a depressed and anxious state with a vaccine that causes a spike in inflammation.
Researcher George Slavich said, "Depression does involve psychology, but it also involves equal parts of biology and physical health."