Here's a question I get quite a bit, which usually goes something like this:
Is ADHD (Attention-Deficit Hyperactivity Disorder) real? Or is it a made-up diagnosis for misbehaving kids?
The short answer is that ADHD (and its precursor, ADD) are absolutely real disorders. They have real neurological underpinnings (including a large genetic component) and real, consistent symptoms. That, I think, is the current scientific consensus.
That said, there is far more controversy over many other pertinent ADHD questions, such as whether or not it's overdiagnosed (approximately 4 percent of show ADHD symptoms), whether it's best treated with stimulant medications such as Ritalin, and whether the disorder should be diagnosed in adults.
One of the most definitive studies of children with ADHD was published in November 2007, by a team of researchers from the National Institute of Mental Health and McGill University. The scientists scanned the brains of 223 children with ADHD and 223 control subjects, from a variety of different age groups. They analyzed these anatomical snapshots for "cortical thickness," which served as a proxy for brain development.
They found that ADHD is largely a developmental problem: the brains of kids with ADHD develop at a significantly slower pace than normal. For instance, the median age by which 50 percent of the cortical points attained peak thickness for the ADHD group was 10.5 years, while the median age for the control group was 7.5 years. This lag was most obvious in the lateral parts of the prefrontal cortex, which is a brain area essential for most of the executive functions that appear to compromised in children with ADHD. (On average, their frontal lobes were three and a half years behind schedule.) The good news, however, is that the ADHD brain almost always recovers from its slow start. By the end of adolescence, the frontal lobes in kids with ADHD have reached normal size. It's not a coincidence that the behavioral problems typically begin to disappear at about the same time. These children are finally able to counter their urges and compulsions. They get better at directing their attention and shutting out distractions. The world is no longer such an overwhelming place.
The larger point is that ADHD is an extreme example of a developmental process that affects everybody. The maturation of the human mind recapitulates its evolution, so that the first parts of the brain to evolve⎯the motor cortex and brain stem⎯are also the first to mature in children. They are fully functional by the time we hit puberty. In contrast, brain areas that are relatively recent biological inventions⎯areas like the frontal lobes⎯don't finish growing until the teenage years are over. The prefrontal cortex is the last brain area to fully mature. In children with ADHD, it simply matures a little bit slower.
For more on related subjects, check out my book or my recent New Yorker article on self-control, which is really about the "strategic allocation of attention".
Brain & Behavior
Comments (12)
I'd be fascinated to learn more about the neurology of ADHD/ADD. So far all I know is that with some ADHD people feel calmed down by dex amphetamines, as well as caffeine, where as for most people it excites them. I'd be fascinated to know why that is.
Posted by: NiroZ | June 10, 2009 8:43 AM