Anna Hodgekiss for MailOnline
09:12 EST, 22 May 2015
09:16 EST, 22 May 2015
A simple infection in the body can have such a profound effect on the brain that a person’s IQ can drop, new research claims.
Danish researchers say the link is very real – and the more infections a person suffers, the bigger the damage to their brain power.
This damage can last for ‘many years’, they warn.
While the effect was seen after infections in any part of the body – for example, the stomach, urinary tract or skin – the most ‘damage’ was seen following infections in the brain.
Catching a simple infection can damage a person’s IQ for several years, a study has found. And the more severe it is, the worse the damage
The researchers found that people who were hospitalised due to infection had an IQ score of 1.76 lower than the average.
And those with five or more hospital contacts with infections had an IQ score of 9.44 lower than the average.
The average IQ is said to be no higher than 115.
The researchers say the study is the largest of its kind to date, and it shows ‘a clear correlation between infection levels and impaired cognition’.
And, unsurprisingly, the more severe the infection, the worse the damage, according to the study, published in the journal PLOS ONE.
Explaining why this effect may occur, study author Dr Michael Eriksen Benrós, of the University of Copenhagen, said: ‘Infections can affect the brain directly, but also through peripheral [surrounding] inflammation, which affects the brain and our mental capacity.
‘Infections have previously been associated with both depression and schizophrenia, and it has also been proven to affect the cognitive ability of patients suffering from dementia.
‘This is the first major study to suggest that infections can also affect the brain and the cognitive ability in healthy individuals.’
He added it may be the immune system that causes the cognitive impairment, not just the infection.
Normally, the brain is protected from the immune system, but with infections and inflammation the brain may be affected.
This is because many different types of infections were associated with a decrease in brain function.
Dr Eriksen Benrós added: ‘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.’
Researchers found that people who were hospitalised due to infection had an IQ score of 1.76 lower than the average. And those who’d suffered five serious infections had a score of 9.44 lower than the average
The research was conducted in collaboration with researchers from the University of Copenhagen and Aarhus University.
It tracked 190,000 Danes born between 1974 and 1994, who had their IQ assessed between 2006 and 2012.
Around 35 per cent of these people had been in hospital with an infection before the IQ testing was conducted.
Commenting on the findings, Dr Eriksen Benrós added: ‘Moreover, 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.’
He hopes that learning more about this connection will help to prevent the impairment of people’s mental health and improve future treatment.
Experiments on animals have previously shown that the immune system can affect cognitive capabilities, and more recent minor studies in humans have also pointed in that direction.