Infections damage intelligence

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MunichSerious infections not only weaken the body, they also have an impact on mental performance. In fact, considerably: on average, people who had to be hospitalized for infectious diseases lose up to ten points on the IQ scale.

It is not necessarily the pathogens themselves that influence the intellectual performance: "Infections can damage the brain directly, but the inflammatory reactions directed against the pathogens can also weaken mental abilities," explains study author Michael Eriksen Benrós from the University of Copenhagen.

Serious loss of intelligence

Data from 190,000 Danes born between 1974 and 1994 were used for the study. They all had their IQ determined between 2006 and 2012. One in three of them had been hospitalized one or more times before the test because of an infection. A comparison of the data showed: the more often this was the case, the greater the mental loss. They ranged from 1.7 IQ points after a single hospital stay to ten lost IQ points after five or more inpatient stays due to an infection.

As expected, diseases that directly affected the brain, such as meningitis, had the greatest effect. But all other forms of severe infections also caused mental performance to decline. "It seems that the immune system itself can affect the brain to such an extent that the IQ is measurably lower for many years after the infection," says Benrós.

Colds and the like do not cost IQ points

There is no need to be afraid, however, of those who suffer more frequently from a milder infection, such as a runny nose. That this would weaken the performance of the thinking organ in the long term is not to be feared, so the scientist when asked by "We found a clear connection between the severity of the infection - measured by the length of the hospital stay - and the cognitive impairment."

The situation may be different with chronic inflammatory diseases such as rheumatism - in such cases, the researcher believes an impairment of the intellectual performance is possible. "We haven't investigated that yet."

It had previously been found that infections can worsen mental illnesses such as depression and schizophrenia. The current study shows for the first time that the brain of healthy people also suffers. “It is all the more important to research which mechanisms are responsible for the connection between the immune system and mental health,” says the researcher.

Presumptuous mind

The intelligence quotient, or IQ for short, is determined using standardized tests. It measures a person's ability to think abstractly, for example in mathematical, linguistic and spatial terms. The tests do not cover other important skills such as creativity or emotional intelligence. The average IQ is around 100. Values ​​between 85 and 115 are considered normal. However, particularly intelligent people can certainly achieve intelligence quotients of 145 - this is where the official scale ends. Anyone who has an IQ of at least 130 can join the cafeteria club of the clever minds. It is estimated that the smartest two percent of the population can do that. (cf)

Source: Michael Eriksen Benros et al .: The Association between Infections and General Cognitive Ability in Young Men - A Nationwide Study, PLOS one, May 13, 2015, DOI: 10.1371 / journal.pone.0124005

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