A large-scale Danish study strengthens the hypothesis that mood disorders like depression are directly tied to inflammation.

Depression and other mood disorders could be the brain’s response to inflammation, according to a new nationwide study from Denmark released Wednesday.

The study, published in the journal JAMA Psychiatry, is the largest of its kind and adds further evidence to the emerging theory that certain mental health conditions could be caused by inflammation.

Researchers found that patients with an autoimmune disease were 45 percent more likely to have a mood disorder, while any history of infection increased the risk of a mood disorder by 62 percent. About one-third of people diagnosed with a mood disorder had been hospitalized in the past for a serious infection.



Inflammation is the body’s protective response to an infection, while autoimmune disorders are inflammatory conditions caused by the body’s overreaction to naturally occurring substances and tissues.

“The associations found in this study suggest that autoimmune diseases and infections are important…factors in the development of mood disorders in subgroups of the patients possibly because of the effects of inflammatory activity,” the researchers wrote.

The new study offers insight into the mechanism of common mood disorders, including depression and bipolar disorder, and may help guide treatment and prevention efforts.