Infections Linked to Mood Disorders Like Depression, Bipolar?Emerging research suggests between being admitted to a hospital for an infection may influence a later diagnosis of a mood disorder.

Specifically, investigators found that the risk of being diagnosed with a mood disorder increases by nearly two-thirds if a person had been admitted to hospital with an infection.

The study, published in JAMA Psychiatry, is the largest of its kind to date to show a clear correlation between infection levels and the risk of developing mood disorders.

Mood disorders include serious mental illness, such as clinical depression and bipolar disorder.

Researchers theorize that an infection may lead to extended mental distress beyond an apparent physical recovery from the original illness. That is, an individual’s distress does not necessarily end once the infection has been treated.

“Our study shows that the risk of developing a mood disorder increases by 62 percent for patients who have been admitted to hospital with an infection.

“In other words, it looks as though the immune system is somehow involved in the development of mood disorders,” said researcher Michael Eriksen Benrós, M.D., Ph.D., of Aarhus University and Psychiatric Centre Copenhagen.

The study is a register study, which has involved following more than 3 million Danes. Between 1977 and 2010, more than 91,000 of these people were seen in a health facility for a mood disorder.

Thirty-two percent of the patients had previously been admitted with an infectious disease, while 5 percent had been admitted with an autoimmune disease.

According to Benrós, the increased risk of mood disorders can be explained by the fact that infections affect the brain:

“Normally, the brain is protected by the so-called blood-brain barrier (BBB), but in the case of infections and inflammation, new research has shown that the brain can be affected on account of a more permeable BBB.”

“We can see that the brain is affected, whichever type of infection or autoimmune disease it is. Therefore, it is naturally important that more research is conducted into the mechanisms which lie behind the connection between the immune system and mood disorders,” Benrós said.

Benros believes knowing more about this connection will help to prevent mood disorders and improve future treatment.

Depression is a mental disorder marked by severe bouts of depressed mood, sadness, lack of interest and pleasure in daily activities, lethargy, sleep problems, feelings of worthlessness and problems concentrating. Bipolar disorder is a mental disorder marked by mood swings that go from depression, to mania or hypomania.

Source: Aarhus University