ADHD gets a mention in New Scientist again this week, along with schizophrenia, autism, depression and a few other disorders. The article is here, but you may need a subscription (so pop out to a good bookshop and read it there before you decide to buy).
Here’s the bit that mentions ADHD:
Such adaptability would have been crucial in the past 50,000 years as our ancestors migrated around the world, and it turns out that the gene responsible for SERT is among many that evolved rapidly during this period (see The 10,000 Year Explosion by Henry Harpending and Gregory Cochran, Basic Books, 2009). The genetic analysis that revealed this dramatic acceleration in human evolution also exposed the rise of another gene variant linked with mental disorder – this time one that helps regulate dopamine, the neurotransmitter associated with pleasure and reward. Harpending and colleagues found that a particular variant of the gene that codes for the D4 dopamine receptor has increased very rapidly in frequency in humans. People with this variant, known as DRD4-7R, tend to have very high energy levels and an increased risk of attention-deficit hyperactivity disorder (ADHD). Yet the prevalence of the variant among certain groups – it is found in 80 per cent of lowland Amazonian Indians, for example – indicates that extra energy has its advantages. “Previously these traits have been highly regarded in some societies,” says Lesch.
“We see a higher percentage of ADHD-associated traits in migratory people, for example.” Like the SERT gene, DRD4-7R can be both a boon and a bane. Some researchers describe such genes as “orchid genes”: nurture them and the carrier thrives, neglect them and a maladaptive personality trait appears. If Spikins is correct, many other genes associated with developmental conditions and mental illness should possess such Jekyll-and-Hyde characteristics. Our ancestors may have benefited from this, but modern societies tend instead to view different minds as a major impediment. “Nowadays, being ‘mad’ is bad,” says Whitley. “In the west, we continue to pathologise difference, and lose its potential adaptive advantage.”
The thrust of the article is that when we were hunter-gatherers spreading out across the world, the characteristics that help be so adaptable and restless were helpful, but in the modern world a lot aren’t, and are now seen as mental illness or developmental disorders. It is an idea put forward by New Scientist before and one we can’t disagree with. Knowing quite what to do about it isn’t quite so easy.