A variety of infections, such as bronchitis, are associated with a higher risk of mental illnesses in children and adolescents, a study published in JAMA Psychiatry found.
The researchers collected data on hospitalizations and prescription medications for the 1.1 million children born in Denmark between Jan. 1, 1995, and June 30, 2012.
For all mental illnesses — excluding depression and bipolar disorder — the researchers found being hospitalized for an infection was linked to a 84 percent higher risk of subsequently being diagnosed with a mental health disorder at a hospital and a 42 percent increased risk of being prescribed a medication for mental illness. The finding suggests infections affect mental health in part by influencing the immune system.
The study also found less severe infections that were treated in an outpatient setting were linked to a 40 percent greater risk of being diagnosed with a mental illness in a hospital and a 22 percent higher risk of receiving a prescription.
But the increased risk for mental illness after infections was less severe when the researchers did an analysis to examine how genetics and home environment influenced patient conditions.
The authors compared outcomes for over 800,000 siblings in this population — siblings who had infections with ones who did not — and found the increased risk for mental illness after hospitalization dropped from 84 percent to 21 percent. The risk of being prescribed a psychotropic medication after hospitalization decreased from 22 percent to 17 percent.
However, the risk didn't drop to zero, study author Ole Köhler-Forsberg, PhD, told NPR. "That's also another finding that made us more confident that there is some link between infections, or the immune system and mental disorders," he said.