The Frontal Cortex

ADHD

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”.

Comments

  1. #1 NiroZ
    June 10, 2009

    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.

  2. #2 J-Dog
    June 10, 2009

    So if it’s all about slow growth, then what’s the deal with Adult Attention Deficit Disorder?

  3. #3 D. C. Sessions
    June 10, 2009

    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.

    (Gross oversimplification follows)

    The brain is a rather ad hoc setup. Impulses (eat that cake!) aren’t gated (not before dinner) as a computer system would be set up. Instead, a separate function inhibits them. In the case of ADHD, the inhibitor appears to be underaroused, so the cake is already eaten before the “maybe I should wait” consideration arises.

    Stimulants raise the general level of arousal, and that includes executive functions. Thus the cake waits for dinner.

    Actually, modest amounts of stimulants seem to help most people with executive function. As Jonah points out, they’re pretty late arrivals and not always at full speed.

    So if it’s all about slow growth, then what’s the deal with Adult Attention Deficit Disorder?

    There’s a lot there. Having the “hardware” to perform executive function doesn’t mean that it’s up to speed, and there are a lot of developmental stages (social skills, for instance) that happen at ages when ADHDers aren’t paying attention. Or maybe it’s just a matter of “slow” lasting for decades.

    One way or another, it’s quite real (from people I know.)

  4. #4 J-Dog
    June 10, 2009

    Thank you D. C Sessions.

  5. #5 D. Clark
    June 10, 2009

    I agree that AD/HD might be largely developmental in nature. But what do you make of Barkley’s researrch that says 60% of AD/HDers experience symptoms into adulthood? Are you saying the most well known researcher in the field is off his rocker?

  6. #6 misunderstood
    June 10, 2009

    This is a huge pet peeve of mine. The idea that ADHD is fake. Permeated by individuals whom think it is just a mere social inept problem or slightly harder functioning issue, so equal to population variability thus it must be a misnomer. My family has a history of ADHD and I have it, my father has it, I’m quite sure my grandmother has it, and other family members as well. Variants of personality, sure. But ill understood symptoms creates misconstrued assessments. What is it like? It is like having extreme short term memory loss for many of us. The amount of house fires, loss of personal items, etc is the actuality of many of my family members experiences. While 90-95% of our functions are fine, it is that 5-10% of our functions that seriously impede our lives, and at are times dangerous. I can not even count how many fires I’ve had in my kitchen, and my father nearly burned the house down by forgetfulness in the kitchen. We don’t want to be seen as damaged individuals, but our daily hardships are real. My son, also has ADHD, and the worst fear I have as a mother, is that he will be hit by a car. He often enough will not look, even at the age of seven, where he is going, or what is around him. He will twirl, karate kick, etc out of shire whimsical fun, right into an oncoming car. And, I am smart enough not to expect all of his symptoms to disappear in his adult life. As stated in the blog, the brain does compensate over time, for that which lags behind. As an adult, symptoms are hidden from the public eye, because cognitive capabilities remind you to use self modification to help you throughout the day. BUT, the clear difference is, a child doesn’t have that maturity yet, the adult does, but the daily hardships aren’t always erased. Adult ADHD does exist, and the above point of brain growth, is what many individuals see on the every day anecdotal experience, but many of the daily mental frustrations are not entirely compensated for.

  7. #7 Terry
    June 11, 2009

    Mr. Lehrer, just finished your New Yorker article,
    very, very fascinating. It should be required reading
    for all parents and teachers.

    It also illustrated one of the many wonders of science.
    That such insight and information could be discovered
    from studying the lowly marshmallow!

  8. #8 sibylle
    June 13, 2009

    Why is ADHD diagnosed much more frequently today than it was years ago?

    Is it due to better diagnostic tools, more awareness of the condition, or has the incidence of the condition actually increased?

  9. #9 Hyperion
    June 16, 2009

    The increase in diagnostic rates has generally correlated with better diagnostic tools, more awareness of the condition, as well as increases in treatment options. Clinical studies that estimate the prevalence of the condition in the general population certainly don’t contradict the current diagnostic rates, and the percentage of the population currently taking ADHD medication is far below the estimated prevalence of the disorder in the population.

    In the past, many people with ADHD would have been diagnosed with some learning disability or another. Others who have ADHD but who are also extremely intelligent would probably be treated as a “little absent-minded professor.” The especially lucky ones wind up being placed in both gifted-and-talented classes and special ed classes. Other times, the kid simply gets labelled as a “troublemaker,” winds up eventually getting suspended or dropping out of school, etc.

    As for the issues of brain maturation, while ADHD is definitely a developmental neurological disorder, and even the diagnostic guidelines note this when they explicitly mention issues of behavior that is “not appropriate for his/her age,” there is also quite a bit of clear clinical evidence that ADHD problems often persist into adulthood. Additionally, PET and SPECT scans have shown functional differences in neurological activity, and SPECT scans have shown differences in catecholamine levels and in the expression of catecholamine receptors and uptake sites….in regions known to be involved in executive functions….and all known ADHD medications target catecholamine receptors.

    So it is likely that there may be structural issues presenting at the synaptic level, aside from differences in brain thickness, that may play a role. This too may be a developmental effect, and certainly would be possible for this to have a genetic cause, especially since many of the genes that appear to correlate with ADHD involve catecholamine receptors and uptake sites (such as DRD4 and DAT10).

    So in addition to a slower rate of brain maturation, there are likely also some issues of faulty wiring that may not necessarily improve as the patient enters adulthood.

    As for people who think ADHD isn’t real….my girlfriend did not believe that ADHD was real when she met me, nor did she believe that medication actually helped ADHD (nor did she know that many of us still have problems with ADHD that persist into adulthood). The funny thing is, it only took a few days with me for her to see the effects of ADHD and the difference that medication makes (she is quite capable of telling when the meds are wearing off and can accurately tell when I need to take my next dose to within 15-20 minutes without looking at a clock, it’s that obvious). When you spend enough time with someone with ADHD, seeing the same behaviors over and over, and seeing that it’s not due to any lack of effort, it becomes a lot more “real.”

  10. #10 jack
    June 30, 2009

    adhd is fake aload of rot its reconized more now cause the drug companies realize they can make more money its not right putting children on these drugs its child abuse and tell me y they concentrate at school but they can always concentrate on computer games and y do most children that have it come from single parents mainly single mothers

  11. #12 another ADHDer
    November 4, 2009

    I cannot stand it when people say ADD/ADHD is fake. I tried to maintain that stance myself for 15 years before I let my mom take me to a psychiatrist to be diagnosed. My dad and brother also have it. None of us can sit still or concentrate for very long unless it’s a very stimulating activity. There is loads of biological/physiological evidence to back up the disorder. None of us take medication, so we’re not supporting the drug companies; you can’t say that it’s all a ploy for them to get more money. We’ve developed coping mechanisms like getting a lot of exercise, breaking projects into much smaller pieces, and allowing ourselves to fidget constantly. We also switch between tasks as soon as we begin to lose focus so we can use the way our brains jump around to our advantage. I also take DHA fatty acids which help me a lot. Anyone who knows us knows ADHD is not fake.

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