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Key points
- Psychologists have long debated whether ADHD is a deficit or a distinct cognitive style.
- A recent review of the evidence suggests that ADHD traits might have helped early humans.
- This evidence should prompt us to consider how we can change our educational systems to benefit, rather than hinder, this cognitive style.
Attention-deficit/hyperactivity disorder (ADHD) is often described by psychiatrists as a neurodevelopmental disorder, one marked by inattention, disorganization, and impulsiveness.
In contrast, some psychologists, psychiatrists, and anthropologists see ADHD not as a deficit or dysfunction but as a distinctive cognitive style, one with its own strengths and benefits.
A recent review of the evidence by child and adolescent psychiatrist Annie Swanepoel and colleagues (2022) makes the case for the latter. They argue that ADHD traits likely evolved in early human environments that rewarded exploration, novelty seeking, and movement, such as nomadic and migrating communities.
If they’re right, this has tremendous implications not only for education but also for how we talk and think about ADHD and other supposed “neurodevelopmental disorders.” Instead of seeing ADHD as a deficit to be fixed, we should see it as a gift to be nurtured.
Evidence for the Evolutionary Thesis
A little over a decade ago, anthropologist Dan Eisenberg and colleagues gathered evidence for the evolutionary thesis. They studied a largely nomadic population in Northern Kenya, the Ariaal. Traditionally, the Ariaal are nomadic pastoralists, but a minority have settled into towns and rely more heavily on agriculture and the market economy.
What Eisenberg found was that, in the sedentary community, those who had ADHD traits tended to be less well-fed and healthy than their non-ADHD counterparts, as measured by their body mass index (BMI).
Incredibly enough, however, among nomadic Ariaal, those with ADHD traits tended to be better fed and healthier than non-ADHD counterparts. He speculated that their fluid attention style would make them more vigilant to potential threats to their herd, to signs of disease or malnutrition, or to sources of food or water.
ADHD traits, such as novelty seeking, exploration, and vigilance, might have been an evolutionary benefit to our ancestors who had to move from place to place in search of new resources while being attentive to threats.
ADHD and Early Human Migration
A second line of evidence for this evolutionary picture comes from the study of early human migrations. This research was led by Chuansheng Chen and colleagues in 1999 and corroborated in 2011.
The conventional view of human evolution is that modern humans evolved in Africa about 200,000 years ago. About 50,000 years ago, many began migrating out of Africa to populate the rest of the world.
Chen found, based on genetic methods, that ADHD traits were overrepresented in these early migrants. People with ADHD traits likely spearheaded the move to populate the earth. It’s unclear whether that’s because people with those traits were more likely to initiate migration, or whether they were better able to adapt to new places.
In particular, Chen studied the distribution of a certain gene variant that is consistently correlated with ADHD traits. He found that this gene variant, which codes for a subtype of the brain's dopamine receptor, tends to be more frequent in contemporary populations with a longer migration history.
Additional evidence for the evolved character of ADHD has come from a 2002 study showing that this particular gene variant has been under “positive selection” pressure for the past 50,000 years. What that means is that natural selection has worked to increase the frequency of the gene associated with ADHD, though it’s not clear whether that is still happening today.
Evolutionary Mismatch or Complementary Cognition?
The evolutionary account of ADHD supports what many psychologists have long suspected: Kids with ADHD tend to thrive when they're given more opportunities for movement and exploration than when they're compelled to sit still for several hours a day.
Based on this sort of research, Swanepoel and colleagues have used the notion of evolutionary mismatch to describe ADHD. A mismatch happens when a trait evolves in one environment because of a benefit, but then the environment changes in such a way that it’s a detriment.
Perhaps ADHD traits were useful in environments involving nomadism and migration, but in modern society, with its demand on having to sit for hours a day and remain relatively stationary, it is a detriment.
The idea of an evolutionary mismatch might be misleading for thinking about ADHD. That's because it might lead us to see ADHD as a kind of “vestige” of an earlier way of life. This might cause us to downplay or overlook the present-day value of ADHD traits.
A concept I find to be more useful here is the notion of complementary cognition, developed by Helen Taylor, complex systems scientist at the Universities of Cambridge and Strathclyde. Think about a termite colony. Termite colonies have three different castes, whose bodies are designed quite differently. Those differences benefit the group.
Taylor has suggested that conditions such as ADHD, dyslexia, and autism might work the same way. From evolution’s perspective, these aren't dysfunctions or diseases. They're differences that make communities thrive.
The notion of complementary cognition raises an urgent question for our society. How can we restructure our educational systems to ensure that kids with ADHD traits can thrive rather than be left behind?
I believe that research such as this is helping psychiatry move out of a paradigm that sees only deficit and dysfunction in mental disorders and toward one that also sees function and purpose.
LinkedIn/Facebook image: Jaromir Chalabala/Shutterstock
References
Swanepoel, A, et al. 2022. Evolutionary perspectives on neurodevelopmental disorders. In Abed, R., and St. John-Smith, P (Eds.), Evolutionary Psychiatry: Current Perspectives on Evolution and Mental Health, pp. 228-243. Cambridge: Cambridge University Press.
