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Motivation, Inattention, and ADHD

The views expressed are those of the author and are not necessarily those of Scientific American.


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Attention Deficit/Hyperactivity Disorder (ADHD) is the most commonly diagnosed psychiatric disorder in children, and is becoming a big deal in adults as well. ADHD is a pile of related symptoms, most of them dealing with motivation, impulsivity, inattention, and, you know hyperactivity (they call it ADHD for a reason). Right now, we treat ADHD with stimulants such as Ritalin and Adderall, which in low doses and when they act over a long period of time can increase focus and help people with ADHD function better.

But the question remains as to what CAUSES ADHD, what abnormalities are going on in the brain that cause the symptoms. There are several hypotheses as to what’s going on. One of them is the dopamine hypothesis, that dysfunctions in dopamine systems are responsible some of the symptoms. But in order to prove this, we have to find evidence for it in humans. There is some evidence that dopamine dysfunction contributes, and now we have a little bit more.

Volkow et al. “Motivation deficit in ADHD is associated with dysfunction of the dopamine reward pathway” Molecular Psychiatry, 2011.

(I should note here that Dr. Nora Volkow is the current head of the National Institute on Drug Abuse, and is also one of the foremost researchers on ADHD in humans).

In this case, the authors wanted to look at how dopamine system function was related to scores of motivation in adults with ADHD. The problem with this is how to measure “motivation”. In this case, they looked at people’s ADHD scores (compared to non-ADHD controls), and looked at scores on personality tests, particularly those related to “achivement”. These are things like

‘works hard,
drives self, enjoys working hard, welcomes difficult
and demanding tasks, persists where others give up,
is ambitious, puts work and accomplishments before
many other things, sets high standards, is a perfec-
tionist’ vs ‘does not like to work harder than is strictly
necessary, avoids very demanding projects, sees no
point in persisting when success seems unlikely, is
not terribly ambitious or a perfectionist’.

They compared these scores with PET images of the dopamine systems of the patients, and correlated the results. PET imagine (positron emission tomography). This imaging lets you take a radiolabeled chemical, inject it in (don’t worry, it’s harmless), and take an image of the results. In this case, they used a radiolabeled chemical that would compete for dopamine receptors, the D2/D3 variety, and one for the dopamine transporter, to look at dopamine system function. These drugs would bind to receptors and give off radiation, allowing them to be seen and produce a picture of receptor availability, and therefore an indirect picture of dopamine system function. The more binding of the chemicals you get, the more glow, and the more receptors are there, and the opposite is true as well.

When they correlated the PET results with the personality tests, this is what they got.

What you can see here is a correlation between “trait motivation” scores and dopamine function in the nucleus accumbens. The more D2/D3 and DAT present, the better the motivation score.

And here is a similar correlation, showing that the better someone’s score on the ADHD symptom test (the CAARS), the higher their trait motivation score.

The authors conclude that the dysruption of the dopamine pathway (defined here as a decrease in D2/D3 binding and DAT binding) is associate with decreased motivation as well as higher ADHD scores.

But the authors note, and I agree, that correlation isn’t causation. But it does suggest that differences in motivation may be related to dopamine function. This in itself isn’t new, dopamine and motivation are known to be related (especially when involving things like drugs of abuse), but the correlation here is a nice bit to add to the current knowledge on ADHD.

But I’m not quite sure what they mean by “motivation”. They used an Achievement Scale of a personality test as a surrogate measure for motivation (because we don’t really have a scale for that). While that’s fine in and of itself, I’m not sure that this is the most accurate measure. Motivation, after all, doesn’t exist in a vacuum. And obviously achievement doesn’t either. While the results may correlate, I’m not sure if we can conclude cause. There are some caveats. For example, children and adults with ADHD do not do as well in school, they have both educational and social difficulties, not to mention dealing with the difficulties of sitting still in the school while attempting to do work. A lot of these difficulties resolve with treatment, but early problems like this could certainly impact how “motivated” the people end up being rated, especially if they are looking at tests like these and thinking of them in terms of academic and job achievement (which they might very well be doing).

I think in this case it might have been better to test motivation for certain things more directly (the authors agree with me, by the way, it’s mentioned in the discussion). You can do this behaviorally in humans using a modified progressive ratio test, having them press a button increasingly for a reward (first M&M costs 2 presses, next costs 4, then 16, then 32, you get the idea). Looking at this kind of persistence, as well as other tasks might help to really look at motivation.

But it could also be something for which you’re never going to be able to really suss out the answer. I mean, ADHD is ADHD for a reason. ADHD patients may well fail the tasks due to distractability, and then you have to ask how distractability and persistence is related to motivation. So while a correlation is good (and dopamine has a good bit to do with motivation and so it’s certainly plausible), and is certainly interesting, I’m not sure we’re at a cause yet. The authors think that this paper helps to establish ADHD as partially a disorder of motivation, but I don’t think you can really separate motivation from lack of persistence and distractability as a result of the disorder. I also don’t think you can talk about motivation in adults as being part of a disorder, when they have grown up with this disorder all their lives. At this point, their experiences may be impacting their motivation, and the correlation may be related to other ADHD traits. While the correlation itself is interesting, I think the concept of “motivation” may be just too much to separate out.

Volkow, N., Wang, G., Newcorn, J., Kollins, S., Wigal, T., Telang, F., Fowler, J., Goldstein, R., Klein, N., Logan, J., Wong, C., & Swanson, J. (2010). Motivation deficit in ADHD is associated with dysfunction of the dopamine reward pathway Molecular Psychiatry, 16 (11), 1147-1154 DOI: 10.1038/mp.2010.97

Scicurious About the Author: Scicurious is a PhD in Physiology, and is currently a postdoc in biomedical research. She loves the brain. And so should you. Follow on Twitter @Scicurious.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. kinnikinick 10:15 am 12/12/2011

    Studies like these, as you point out, often suffer from the tangled loops of causality you get when brain affects mind and mind affects brain.
    As someone who was diagnosed with ADD in his 40s, I’m constantly aware of my own skewed view of motivation and success. If you don’t have the mental tools to consistently shape your own future, notions of persistence and achievement can seem like a cruel joke; much less painful to “live in the moment” and avoid the cognitive dissonance. Of course, this means you never develop the skills needed to live any other way.
    I’d be interested to see whether dopamine levels would change in a hypothetical study using eg. cognitive behavioral methods to help improve perseverance in people with ADD. I’d sign up; I know from my own experience that Ritalin alone isn’t enough.

    Link to this
  2. 2. candide 11:50 am 12/12/2011

    What, could you repeat that? Oh the hell with it…

    Link to this
  3. 3. dvjenkins 12:36 pm 12/12/2011

    My read of those graphs indicate the researchers were highly motivated to find a correlation.

    Link to this
  4. 4. Nyx01 12:58 pm 12/12/2011

    It think there is a fatal flaw in the personality trait test. The fact is, I literally fit both profiles, depending on the circumstances. Writers of such tests like to skirt this problem by telling you to pick the one most frequently occurring, or whatever fits best, or some such nonsense, but in my opinion that does not provide an accurate picture of what is going on. I have been capable of enormous ambition in my life and was able with great difficulty to not only go to law school but graduate number 1 in my class. At work, I am known as a perfectionist, even when it is not always a good thing to be a perfectionist. However, I put off certain kinds of projects, and projects that require great organization are intimidating. I cannot organize my physical space. I am intimidated by dirty dishes. It took me 10 years to complete my bachelors degree. I avoided college papers until the day before and then stayed up all night long trying to write them in one go. I switched majors repeatedly. I missed out on scholarships and even financial aid because I couldn’t get the applications done. I was in the honors program but didn’t finish it. My teachers used to shake their heads and say, “She has so much potential. What a waste.” So … this personality trait test is offering a false dichotomy. I don’t know how to fix it, but it’s just not right.

    Link to this
  5. 5. scicurious 1:36 pm 12/12/2011

    @kinnikinick I think I agree with you. In this study they used adults who were as yet entirely untreated. I wonder how adults who were diagnosed as children and treated as children would look, I think it might be different.

    Link to this
  6. 6. aidel 4:17 pm 12/12/2011

    Sci, as you said, the problem of coming up with an acceptable definition of motivation is totally vexing. Can you imagine one that would work cross-culturally? I can’t. And Nyx01 you are also right about the spurious personality trait tests (not unlike IQ tests, on which I have scored both “very superior” across the board (which is a joke) and also “average,”). Perhaps ADD is more physical than chemical — not all gets “pruned away” during late adolescence that should. That might explain why some very bright people start off in one direction with a particular goal in mind and end up somewhere very, very different. (As opposed from being lack of hard work or ‘motivation.’)

    Link to this
  7. 7. masamune2823 9:19 pm 12/12/2011

    @nyx01 I think you’re onto something there. One important concept that fails to be mentioned in such discussions is how the task at hand is perceived; as something thats just necessary without any real reward (like doing well in school, cleaning, or doing paperwork) or something thats perceived as producing immediate or close to immediate reward (like doing well in LAW school and ending up with a 100K a year job). The difference between immediate reward vs. eventual reward/no reward seems to be missing from the discourse in such studies. Rather,they clump the motivation to do tasks into one without looking into (ironically) the motivation for those tasks

    Link to this
  8. 8. NorthernPhysics 5:00 am 12/13/2011

    I was diagnosed with ADD back in ’96 just before I graduated high school. To most people I come of as a fairly bright person. They don’t know the mountain of classes I’ve failed from high school on. For me the trouble is that I’ve chosen to study physics (because I am passionate about it) which is completely incompatible with ADD. Not only do I need focus and mental discipline I need it in spades. Sufficed to say the blunt tool of stimulant medication was unsuccessful. With the exception of one year off after being kicked out of college for poor academic performance I spent the years between ’97 and ’09 earning a B.S. in physics. I was on academic probation for 7 years… I could go on. Lets just say ADD really bites and the progress toward understanding it is pathetic.

    Link to this
  9. 9. Meta4 9:40 am 12/15/2011

    Great analysis! Defining motivation (or the lack thereof) in the context of ADHD is indeed complex. In my experience, another way to look at the deficit is that it’s difficult to be motivated in one specific direction when you are faced with a multitude of paths, many of which appear to be equally important.

    For me, it isn’t a lack of motivation, it’s a lack of focus.

    Link to this
  10. 10. Karen Dee 7:31 am 12/17/2011

    Don’t get me wrong by the following writing. I respect science when the basis of it is solid science, but some science has lost it’s way from the original basis of what it is to be. Some science has become nothing more than an elaborate abstract construction of thoughts. These thoughts and beliefs attached to them have huge impacts on the way we behave and actually can be a creation and self fulfilling prophecy of our behaviors. That said, check out more creative writing like below at
    karendee57.wordpress.com

    SO MUCH FOR OUR REASONINGS OF HUMAN BEHAVIORS…..

    When a 60 year old man or woman forgets what he’s doing and absentmindedly doesn’t complete a task but instead gets distracted and carried away with something else, they call it forgetfulness, senile and old age.

    When a young child does it they call it ADD and hyperactivity.

    When a young woman does it, they call it being an airhead, or being blonde, even if she is brunette.

    When a young man does it, they say it is because he has nothing but sex on his mind.

    When a baby does it, they call it part of a developmental stage and tell you he’ll outgrow it.

    When a teenager does it, they might call it adolescence, caused by either irresponsibility, peer pressure distractions and hormones.

    When a academic professor does it, they call it absentminded, knowing
    he has some other important intellectual thoughts going on in his head.

    When a CEO, Executive or Employer/Boss does it, they believe it happened for good reason and because he has more important things to do. They also ask why his assistant hadn’t been on top of things and call on her to get the task completed for him.

    When a black man does it they call it being lazy.

    When an emotionally upset person does it,they call it compulsive behavior.

    When a mother does it, they call it having too much to do.

    When a father does it at home, they don’t call him anything but dad and wait for mom to clean up after him.

    When a battered woman does it, they call it being traumatized.

    When a clown does it, they call it part of the act of being a clown.

    When a __________________________.

    When a __________________________.

    When a __________________________.

    Etc.

    Link to this
  11. 11. jcgarrett 11:26 pm 05/3/2012

    I’m afraid you misreported on the article. In fact, the study does not say that ADHD is associated with decreased dopamine functioning (they don’t report the correlation between ADHD scores and the dopamine-related measures), but in fact that motivation is associated with dopamine functioning in ADHD patients.

    Link to this
  12. 12. imhanna 3:36 am 06/18/2014

    Children and Adults both diagnosis criteria are quite different, I think we should check this once: http://adhdinadults.com/adhd-in-adults-treating-adult-adhd-in-primary-care-brendan-montano-md

    Link to this

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