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Infections tied to mood disorders

Autoimmune diseases and infections increased the risk for developing mood disorders, new data suggest. Researchers said hospital contacts with infections may account for up to 12% of mood disorders if the effect is causal, but their findings must be confirmed.

"Clinicians need to pay attention to somatic diseases in patients with psychiatric disorders, and even if the relationship is not causal, treatment of underlying somatic diseases may improve the symptoms and quality of life," Michael E. Benros, MD, of Aarhus University in Denmark, said in an interview.

 

Michael E. Benros

In a study that included 3.56 million people, Benros and colleagues estimated the risk for mood disorders among those who visited the hospital for autoimmune diseases, such as autoimmune hepatitis and celiac disease, and infections, which included sepsis, hepatitis, gastrointestinal infections, skin infections, respiratory infections and pregnancy-related infections.

A total of 91,637 people in the study were diagnosed as having a mood disorder, including depression and bipolar disorder. Of those, 29,194 (32%) had contact with a hospital for infection before the mood disorders diagnoses were made, and approximately 5% had visited the hospital because of an autoimmune disease.

Hospitalization for an autoimmune disease elevated the risk for developing mood disorders by 45% (incidence rate ratio [IRR]=1.45; 95% CI, 1.39-1.52), and infection raised the risk by 62% (IRR=1.62; 95% CI, 1.60-1.64), compared with no hospital visits.

Hospitalization for both autoimmune diseases and infections increased the risk for subsequent mood disorders even further (IRR=2.35; 95% CI, 2.25-2.46).

The researchers also observed that the risk for mood disorders increased with number of times an individual had contact with a hospital for an infection. For example, one hospital visit for an infection conferred a 43% (IRR=1.43; 95% CI, 1.40-1.45) increased risk for developing a mood disorder vs. eight or more visits, which carried more than three times the risk (IRR=3.36; 95% CI, 3.06-3.68).

The researchers said inflammation from the infection or autoimmune disease may affect the brain, increasing the odds of developing a psychiatric disorder such as depression. However, the reasons for the interaction between infection and autoimmune disease and mood disorders are not fully understood.

“Although the hypothesis of an immunologic contribution is interesting, it remains unclear precisely how the immunologic process affects the brain and whether it is a causal relationship or an epiphenomenon of underlying genetic, psychological, or non-immune-related mechanisms,” the researchers wrote.

Disclosure: One of the researchers reports financial ties to Bristol-Myers Squibb and Janssen-Cilag.