Disease and the Brain

“In human newborns, the brain demands 87 per cent of the body’s metabolic budget.”

This is the opening line of a paper recently published in the “Proceedings of the Royal Society of Biological Sciences,” and it is on this line that the paper’s argument hinges. In the paper, the authors propose a new theory for cognitive ability (i.e. IQ) differentiations across the globe. According to their “parasite-stress” hypothesis, there is a direct correlation between infectious disease prevalence in a given region, and IQ scores.

Previous theories explaining IQ distributions have ranged from a country’s health and education systems to its gross domestic product. My favorite theory (its hard to type with sarcasm, but just know I’m currently doing it), claims there is a direct correlation between colder temperatures and increased IQs. According to the theory, only individuals with relatively high intelligence can survive in colder regions, as they must overcome more severe obstacles. As much as I want to believe that people from colder regions are smarter than those from hotter (I’m from Minnesota), I just don’t believe that colder regions present more of a challenge to survival than hotter ones. For example, aren’t hotter regions more likely to have more prevalent infectious diseases?

Infectious diseases sap enormous amounts of energy from their hosts through various means, including tissue destruction, diarrhea, and immune system exhaustion. For this reason, contracting a disease early in life can be extremely threatening to brain development, this new paper claims. According to the study, disease prevalence, more than any other factor (i.e. temperature, distance from Africa, GDP, etc.), directly correlated to inhibited cognitive development.

If disease is completely eradicated, then will everyone be a genius? I would guess no. Early exposure to diseases robs the developing brain of the energy it needs to reach its full potential. That being said, not everyone has the same potential for brain development. Energy availability is not the only factor in play. There are a variety of other genetic and epigenetic factors at work in and on all of us.