Monday, April 16, 2012

UneXXpected Science: Does ADHD have benefits in certain environments?


Mmmm. Novelty seeking. (Source.)

Anyone who has ADHD—attention-deficit/hyperactivity disorder—can tell you the stories. Stories of getting into constant trouble, hearing “sit down, sit still, be quiet” repeatedly, endlessly, feeling the urge to move, touch, jump, talk, roll, do anything but sit quietly at a desk, working on math. And, as anyone who has ADHD can also tell you, these traits often don’t exactly help you get ahead in modern society. School requires stillness, attention, focus on pencil and paper work. Most jobs require focus, attention, sometimes an ability to tolerate the sheer boredom of four walls of a grey cubicle for eight hours each day. Most people would struggle with that, but with attention deficit, it's more than a struggle.

A cubicle environment obviously is probably not the best place for someone with ADHD, although it may be beneficial in less boxy workplaces. And school can be a long, troubling, negative process, as well. People used to blame the parents of children with this disorder, laying the cause of ADHD at the feet of poor parenting--and some are still trying to lay that blame. Science has something else to say about it, having demonstrated that genes are actually the primary contributors to ADHD, specifically genes that encode proteins whose job is to “receive” messages from a brain chemical called dopamine.

Dopamine signaling underlies all kinds of behaviors, but primarily it is known for its involvement in reward pathways, novelty seeking, and addiction. Specific forms, or alleles, of dopamine receptor genes have been strongly associated with ADHD, and this disorder can be viewed in many cases as a constant search for reward and novelty, a search that can translate as inattentiveness or hyperactivity.

Given that this dopamine-based manifestation is rooted in genes, the question arises of why it has persisted in humans throughout our evolution. If we look around at modern society, it’s easy to see that ADHD behaviors generally are not conducive to being one of the “fittest” in many situations that take up most of our time. Yet, there has been enough associated advantage for these gene forms to persist and allow their carriers to reproduce and pass them along to offspring.

And that’s where we need to think in nature’s evolutionary terms. Modern society is just that—modern. This way of life has only been around for, at most, a few thousand years, which can be a blink of an eye for processes of natural selection. Dial back time about 10,000 years or 20,000 years, and you’ll be hard pressed to find any humans living in an environment anything remotely like a cubicle.

Natural selection results from the interaction of genes and environment, and the "selection" Nature's making is for an individual's genetic makeup to have some representation in future generations. To look at this process through Nature's lens, take the gene forms associated with ADHD and place them in a different environment and ask the question: Do they help or hurt or make no difference at all?  

This question is exactly what researchers addressed when they looked at the effects of an ADHD-related gene form on a group of nomadic people, the Ariaal, in Kenya. Some members of this population had, in only the last few decades, made a transition to a sedentary, city-type lifestyle. Others continued to live the fast-moving, nomadic existence of their herding ancestors.

Researchers looked at a version of a dopamine receptor called DRD4-7R, which also has been implicated in autism symptoms in people with ADHD. They found that city dwellers with this form of the gene didn’t fare as well in health as their sedentary cousins without it. But the Ariaal who continued their nomadic existence and carried the 7R form of the gene fared better than those nomadic tribesmen without it. To assess health, the researchers looked at body mass index and other factors. 

The results suggest that there might be some benefit to ADHD in the backdrop of a nomadic culture. although a more recent analysis of several studies together suggests a different form of this receptor may have an ADHD association (this kind of study, called a meta-analysis, doesn't provide new data but synthesizes existing data). 

Regardless of which gene forms are involved, you can imagine that in a nomadic culture, it might be useful to be always looking around, seeking novelty, thriving on the rewards of changing behaviors, defending food, and being always on the move. Someone with ADHD likely would be far better fit for this kind of lifestyle than would the best desk jockey in the world. This interesting study demonstrates that when it comes to some of the neurological developmental manifestations we call “disorders,” how negative or positive they are may be a matter of environment.


By Emily Willingham, DXS managing editor 

2 comments:

  1. This is fascinating. My son's learning environment is our home and the world. It's free-range learning. The constant moving doesn't *interfere* with his learning; it helps him learn.

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  2. Brenda...thanks for commenting. We also do schooling at home, and my son gets to move, stand, wiggle, etc., as much as he needs to focus himself. Works pretty well.

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