Dealing with an infection lowers your IQ for up to 15 years

Dealing with an infection lowers your IQ for up to 15 years

By Ryan Whitwam May. 26, 2015 9:30 am human brain on white background

A new study conducted in Denmark makes the bold claim that infections can lead to a decrease in your cognitive ability severe enough to show up on diagnostic exams like an IQ test. The researchers say that not only is the effect of infections on IQ consistent, it becomes more profound the more infections you have.

The study consisted of more than 180,000 participants thanks to Denmark’s universal health care system. A little more than a third of the people in the study were diagnosed with a general infection at a Danish hospital between 1977 and 2012. Those who presented with infections showed a slight decline in cognitive ability compared to the average, with the IQ measurements made in 2006-2012. The effect was small — a single infection dropped the IQ of participants by 1.76 points, but those with five infections saw an average reduction in IQ of 9.44 points.

Because of the nature of the study, researchers didn’t have before and after measurements of each person’s IQ. That would be the ideal way to conduct this study, but the paper downplays the role of self-selection (i.e. those with lower IQ are more likely to contract infections). There was a strong correlation of IQ with the time since infection. The effect on cognitive ability was more severe closer to the time of hospitalization — a hospital visit less than a year before testing resulted in a score nearly three points below average. The effects were measurable up to 15 years after infection.

So assuming this effect is real, what’s going on? The researchers believe this is a consequence of inflammation. Infections can work on the brain directly, of course, but the systemic inflammation of an immune response could also change the way the brain functions. The infections observed in the study come in all different sorts, so the only thing they really have in common is the way our immune systems react.

This is certainly an interesting study, but even with the large sample size, it needs to be verified with independent testing. If the results are confirmed, this could change the way we treat infections and psychological disorders.

Leave a Reply