Childhood infections may decrease IQ scores
TUESDAY, JUNE 02, 2015 11:06 AM

Hospitalizations are rarely a good thing, but a recent large-scale study has revealed another negative outcome of some hospital visits: a decrease in IQ scores. The study, published in the scientific journal PLOS ONE, researched around 190,000 men in Denmark, all of whom were required to take IQ tests at age 19 to sign up for the country's military draft. Researchers found that the more times someone is hospitalized for an infection during childhood, the more likely they will be to have a lower IQ score later in life. Read on for more of the study's findings.

How much do infections affect IQ scores?
According to the research, about 35 percent of the men participating in the study had been hospitalized at least once for an infection in childhood. These men had an average IQ score of 1.74 points lower than the other 65 percent. What's more, the type of infection and number of hospitalizations could have an even larger affect on intelligence. In fact, men who'd been hospitalized more than five times had IQ scores more than nine points on average below those who hadn't been hospitalized at all. Bacterial infections lowered IQ scores by an average of 1.55 points, while viral infections had a slightly less negative effect - a decrease of about 1.34 IQ points. 

Why do infections influence cognitive abilities?
The results concluded that infections had an obviously negative effect on a person's cognitive abilities, but why is that? As one might expect, infections in the brain had the largest influence on cognition, but infections in other parts of the body were even related to decreased IQ. Researchers say that's because any time the immune system is affected, cognition is as well. 

"It seems that the immune system itself can affect the brain to such an extent that the person's cognitive ability measured by an IQ test will also be impaired many years after the infection has been cured," researcher and study author Dr. Michael Eriksen Benrós said in a statement. 

Researchers believe that the immune system's response to an infection can cause inflammation, which affects the brain physiologically causing that decrease. However, they say that more research should be done to determine just how much the immune system influences cognition and even psychiatric disorders. Past research has linked inflammation to depression, schizophrenia and dementia. 

"We can see that the brain is affected by all types of infections. Therefore, it is important that more research is conducted into the mechanisms which lie behind the connection between a person's immune system and mental health," Eriksen Benrós concluded.