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Caffeine for ADHD

“I don’t want to give my child any drugs or chemicals for their ADHD,” says a parent. “Instead, I’m thinking about using caffeine. Sound strategy?”

It may be dispensed by a barista and not a pharmacist, and the unit sizes may be small, medium and large, but caffeine is a chemical and also a drug, just as much as methylphenidate (Ritalin) is. Caffeine is even sold as a drug — alone and in combination with other products. But I regularly speak with consumers who are instinctively resistant to what they perceive as drug therapy — they want “natural” options. Caffeinehas been touted as a viable alternative to prescription drugs for ADHD. But is caffeine a science-based treatment option? This question is a good one to illustrate the process of applying science-based thinking to an individual patient question.

I’ve already described my personal fondness of caffeine, particularly when it’s in the form of freshly-roasted coffee. I’m not alone in my love. Caffeine is the most widely consumed drug in the world — more than alcohol, and more than tobacco: 90% of adults worldwide consume it daily.  The average American consumption is 280mg per day — about two cups of coffee.  The main source is coffee, but tea consumption is growing. And caffeinated soft drinks and energy drinks are a growing source of caffeine for children. Why do we love it so much?

Caffeine is quickly absorbed once consumed — and it immediately gets to work stimulating neurotransmitter release. Besides psychiatric effects, it has effects on alertness (positive), headache (also effective, except in withdrawal situations), athletic performance (another win), the cardiovascular system (my fingers are crossed), and the endocrine system, where it may improve diabetic control. It’s also being studied for effects on the gastrointestinal system, as well as its impact on cancer risk. In adults, caffeine consumption is associated with a negative relationship with all-cause mortality, largely due to a reduction of cardiovascular effects. Causation hasn’t been established though. Most of you are very familiar with the side effects of caffeine: agitation, tremors, insomnia, headache. Overall, despite documented cases of dependence and withdrawal, caffeine consumption has a generally attractive safety profile with a wide therapeutic range.

The symptoms of Attention Deficit Hyperactivity Disorder (inattention, impulsiveness and hyperactivity) have been identified for at least 100 years.  But once the diagnosis appeared in the DSM-IV, its standardized criteria became commonly used, and the prevalence is now estimated at about 3-7% of children. The term Attention Deficit Hyperactivity Disorder is somewhat of a misnomer, as the dysfunction appears related to an inability to regulate attention — not a deficit. Magnetic resonance studies suggest ADHD may manifest as a weakening of inhibitory signalling in the frontal cortex.The cause appears most likely to be genetic, with environmental influences.

The two main interventions for ADHD are behavioural treatments and drug therapies. The traditional therapies are the stimulant drugs, including amphetamine (Adderall), methylphenidate (Ritalin), and dextroamphetaime (Dexedrine). Some have been in use since the 1960’s. Over time, a wide array of dosage forms including controlled-release versions have emerged, driven by the desire to stabilize blood levels. The basic drugs themselves are short-acting, leading to a fluctuation of effects and the need for mid-day treatments — not ideal for school-age children. Non-stimulant drug therapies (e.g., antidepressants) have more recently emerged as treatment options and may be combined with stimulants, as additional therapies where symptom control isn’t reached with stimulants.

The treatment goals with ADHD are symptom based, so dosing is dependent on the effects observed. Treatment goals usually include reductions in disruptive behaviours, improvements in relationships (with peers, siblings, teachers, and parents), or specific academic parameters. Ideally, treatment goals should be objective and measurable, and agreed-up by parents, teachers, physicians, and children.

The stimulant medications have an impressive safety record and are generally well tolerated. There’s a long history of use. Are they effective? There’s reasonably good data to suggest they are, although comparative data are lacking. [PDF] Response rates to ADHD treatments appears high — 60-80%, and side effects are generally mild and manageable.

So that brings us back to the original question — I developed a focused clinical question using the PICO framework:

  • Patient: Who are what are we treating? In this case, children.
  • Intervention: What are we treating with? Caffeine
  • Comparison: Compared to what? Let’s assume stimulants.
  • Outcome: The effect we want to measure. In this case, symptomatic control.

So the question may be summarized as: In children, how does caffeine compare to stimulants for symptomatic control of ADHD?

It’s helpful to start with pharmacology to consider plausibility before we look at clinical trials. Caffeine, or more properly, 1,3,7-trimethylxanthine, has central nervous system effects, mainly thought to be due to blocking adenosine receptors in the brain. Given we don’t know the specific mechanism of action of the ADHD drugs, I’ll accept caffeine as a plausible treatment: it crosses into the brain, and it has CNS stimulant effects.

So let’s look at the data. I started with a tertiary reference: the Natural Medicines Comprehensive Database rates caffeine as “possibly ineffective”. Then I went to PubMed, and ran my own search.  Are there placebo-controlled, or head-to-head trials? Yes, and they’re disappointing:

The data are limited by small trials, mostly conducted in the 1970s. There doesn’t appear to be many trials exploring the dose-response relationship, and trials don’t seem to titrate doses — so it’s not clear if we’re evaluating comparable doses. While there don’t appear to be any systematic reviews, there are trials comparing caffeine to other drugs. In one comparison, 20mg of methylphenidate was found to be superior to 160mg of caffeine. In another trial, seventeen children who had positively responded to stimulant drugs were trialed on placebo, or two different doses of caffeine.  Caffeine didn’t have any statistically significant effects on behavioural measures.  In a trial  comparing amphetamines to 600mg caffeine daily, plus amphetamines,  caffeine was reported to provide incremental benefit, but side effects were noted. That’s not surprising: 600mg is the caffeine in two Starbucks Grande-sized coffees.  A double-blind crossover examination of caffeine, methylphenidate, and dextroamphetamine in 29 children concluded that while the two stimulants had meaningful effects, caffeine was indistinguishable from placebo. Overall — no strong signals of efficacy in the evidence.

Conclusion

Caffeine is a questionable treatment option for ADHD. There is mixed to negative efficacy data, and no long-term safety information in children. Depending on the form given, there’s challenge of ensuring standard doses (especially when using coffee) and maintaining stable blood levels.  In comparison, prescription stimulant medications offer a variety of drug  choices that have more convincing efficacy data, and are accompanied by a long history of use. There’s also a wide array of product types, making it easier to customize a treatment regimen. So while I can understand the hesitation to medicate and to “go natural” instead, it’s not a trade off that’s attractive. “Go science” instead — look to the data, and make treatment decisions based on the best evidence.

 

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20 thoughts on “Caffeine for ADHD

  1. Ed Whitney says:

    A bit off the topic of ADHD, but theophylline and caffeine are both members of the methylxanthine class of compounds, and caffeine is a weak bronchodilator. This does not mean that you treat an asthmatic child with a morning pot of brewed coffee. You do need to know about a patient’s coffee consumption to optimize your interpretation of pulmonary function tests, though.

  2. cervantes says:

    This may be confounding by indication, but . . .

    2. 3-year followup of the NIMH MTA Study. Jensen, P. Journal of the American Academy of Child and Adolescent Psychiatry 46 (2007):989-1002.

    At the end of 14 months, core ADHD symptoms were reduced more in the children treated with stimulants than with behavioral therapy. However, at the end of three years, “medication use was a significant marker not of beneficial outcome, but of deterioration. That is, participants using medication in the 24-to-36 month period actually showed increased symptomatology during that interval relative to those not taking medication.”

    3. Mta at 8 years. Molina, B. Journal of the American Academy of Child and Adolescent Psychiatry 48 (2009):484-500.

    At the end of six years, medication use was “associated with worse hyperactivity-impulsivity and oppositional defiant disorder symptoms,” and with greater “overall functional impairment.”

  3. psychres says:

    Perhaps the perspective of treatment comparisons misses the point. In the case of children, the most common (reversible) cause of ADHD like symptoms is sleep deprivation. A 2008 study showed over 70% of kids with ADHD had some degree of sleep problems (1).

    Studies that show treatment of sleep disorders in children with ADHD also show resolution of ADHD symptoms (2,3). Sleep disordered children and adults have impaired executive function. This is due to reduced activity of the frontal lobes with sleep deprivation.

    This may underscore the reason to use stimulants in the first place. They are the only treatment that can improve the executive function of the frontal lobe.

    The logic of the treatment comparisons in the”Caffeine for ADHD” article is sound. But the treatments compared are limited to drugs. Given the possible etiology, it may explain why tonsillectomy (for obstructive sleep apnea) could be superior to both methylphenidate and caffeine.

    The underlying issue of sleep deprivation in children may be of greater importance versus the choice of stimulants.

    Refs:

    1) Sleep problems in children with attention-deficit/hyperactivity disorder: prevalence and the effect on the child and family. Arch Pediatr Adolesc Med. 2008 Apr;162(4):336-42Sung V, Hiscock H, Sciberras E, Efron D.

    2) A long-term open-label study of dopaminergic therapy in children with restless legs/periodic limb movements in sleep and ADHD. Dopaminergic Therapy Study Group. Pediatr Neurol. 2000;22:182-186. Walters AS, Mandelbaum DE, Lewin DS, et al.

    3) The effect of tonsillectomy and adenoidectomy on inattention and impulsivity as measured by the Test of Variables of Attention (TOVA) in children with obstructive sleep apnea syndrome Otolaryngology – Head and Neck Surgery, Volume 131, Issue 4, 367-371 G.Avior, G.Fishman, A.Leor, Y.Sivan, N.Kaysar, A.Derow

  4. Ed Whitney says:

    Related to methylphenidate for ADHD is its use in the setting of traumatic brain injury (TBI). I would appreciate any insights readers of this site may have about interpreting studies of medication for this indication.

    My main problem is that the outcomes in these studies are reported as scores on various batteries of neuropsychological tests. Frequently, the studies use a crossover design. Patient who receive the active drug first and the placebo second will appear to have a weaker treatment effect of the active drug because of practice effects: when we do a test the second time, we generally do better than we did the first time. Similarly, the group which is randomized to placebo first and then active drug will appear to have a stronger treatment effect because the second test measures both the drug and the practice effects simultaneously. When the scores are averaged, I do not think that there is likely to be bias in the direction of inflating the drug effect. The measured treatment effect of the active drug may even be conservative. Does this make sense to anyone? Actually, studies tend to have several alternating test and treatment periods which are averaged for each participant in the trial. But I do not know of any published literature about this problem. References would be most welcomed!

    I would expect the size of the practice effect to depend on the specific tests employed. Some tests are somewhat easier the second time you take them, and some tests are probably a great deal easier the second time. In the studies I have read, the discussion section of the article does not delve into this issue. There may be statistical methods for adjusting the treatment effects, but I do not know what they are. Any suggestions?

    I would expect similar issues to arise in the interpretation of studies of treatment effects in children, so I hope this is not entirely out in left field.

  5. Interesting article. Thanks. I think psychres has a good point. It seems that attention problems due to obstructive sleep apnea is becoming more widely recognized, hopefully this will be of some use in treatment. It certainly seems to be something that craniofacial plastic and ENT surgeons are more aware of these days.

    Concerning caffeine. I have a friend who has two children with ADHD (one also has obstructive sleep apnea). The older one is taking medication (not sure about the younger), but my friend swears that the caffeinated drink that the son consumes after school really helps him through the after school medication dip that many kids seem to have.

  6. ineri says:

    I believe that ADHD is being very much over-diagnosed, and current symptomatic treatments should switch to changes in the environment.
    (Apologies for not providing references) The reason being, first, kids born later in the year are more likely to get the diagnosis, because they are on average less mature than their peers and are more likely to show similar signs as ADHD, just because it is harder for them to follow the average velocity of the class. Having a more fine grained division than yearly might help. (Also, especially with hyperactivity, just give the kids more physical exercise opportunities).
    Second, when given immediate positive feedback on performance kids with ADHD have been shown to outperform ‘normal’ peers.
    Third, from personal experience, many persons I know that were diagnosed with ADHD were actually very bright but totally didn’t fit into the normal school system.
    Myself, I was completely bored and restless throughout the elementary school, and I’m quite convinced that I would have been young today, I’d have been on some medication.

    That said, I do believe there are cases where medication makes sense, but noway near the quoted percentages here.

  7. Calli Arcale says:

    ineri:

    Third, from personal experience, many persons I know that were diagnosed with ADHD were actually very bright but totally didn’t fit into the normal school system.

    ADHD doesn’t mean stupid and never has; I know some people are surprised to learn that kids with ADHD can be smart, but that’s completely untrue. Many of them are very smart. (Not all of them, of course. They’re like other people that way.)

    The condition does make it difficult to fit into a rigid classroom structure. Structure is important for a kid with ADHD, but they may have great difficulty adapting to a particular structure. That’s not to say that all misfits have ADHD, of course.

    As an adult with the condition and the parent of a child who has it also, I can anecdotally attest to the effectiveness of methylphenidate. Caffeine isn’t totally useless; it does for us what it does for everyone else. But it’s not a replacement for stimulant treatments. I suspect that if researchers were to study the difference between caffeine and the various effective treatments for ADHD, they might find clues that would point to why the hell the stimulants work at all.

    One interesting thing I’ve read about in studies — stimulant medications work on attention problems if you have ADHD. Otherwise they really don’t. Also, certain other conditions (overwork combined with way too much multitasking, sleep deprivation, etc) can mimic ADHD symptoms but do not respond as well to medication — the real problem needs to be corrected in those cases. So maybe ADHD treatment should shift to first attempting to treat major “pseudo-ADHD” problems like sleep problems before moving on to medication. I’m not a big fan of diagnosis by trying different treatments until something works, but until a better way to distinguish ADHD from the mimics comes along, it might be prudent.

    Regarding studies which showed greater problems from kids on medication than kids not on medication, I’m not really surprised. I doubt the kids were put on medication at random, after all. It’s like arguing that having special level III EBD* classrooms is ineffective because after six years, kids who were in those classrooms are more of a wreck than kids who weren’t. Well, yeah. They’re level-III EBD. It’s not something you can just talk a kid out of.

    *Emotionally-Behaviorally Disturbed, the most challenging group for a special ed teacher, and also the most likely to result in a workman’s comp claim

  8. @ Calli – a while ago I was reading how anxiety disorders and ADHD can look very similar in children. A child who is anxious can have difficulty focusing or be very ridged in their expectations, impulsive, temper tantrums, hyperactivity, etc sleep troubles can acerbate either condition. Or the child could have both issues or a learning disability instead (or along with). Also, just to throw another wrench in things, kids with even mild hearing impairments can have behavior issues, learning issues, impulsive, hyperactivity…due to the communication issues and listening fatigue.

    Certainly not an easy thing to diagnose.

  9. Thaumas Themelios (Wonderist) says:

    I was recently diagnosed with ADHD as an adult. Prior to my diagnosis I was a caffeine junkie (and didn’t know why) because it seemed to help me concentrate. But it didn’t do the job well, and the side effects including addiction were nasty.

    One of the key problems with caffeine is that ADHD, especially in adults, tends to have a high co-morbidity rate with anxiety, depression, and other things. Caffeine, unfortunately, can strongly trigger anxiety (going from feeling ‘wired’ to feeling ‘frazzled’ and ‘gotta get out of here!’). And feelings of anxiety can strongly interfere with focus and attention, making tasks harder, and ironically making the overall ADHD situation worse, rather than better. Sure, you feel more alert, but all that alertness just gets funnelled into worry and distractedness, if you already have anxiety, which many ADHD adults do.

    The great thing about the meds like methylphenidate (I’m on Biphentin) is that they increase focus and attention far better, but without increasing anxiety (not nearly as much as caffeine does, in comparison). In fact, I feel much more relaxed and able to deal with stressors when on my meds.

    The one episode which really drove this home for me was when I had just started taking medication (I started on Dexedrine) and was trying to focus on a problem at work. So I thought, I’ll just drink a coke to ‘top me up’ so I can get this thing done.

    I nearly had a panic attack! It turns out that adding caffeine to meds does not help with attention, it just gives you all the side-effects, but amplifies them, because you’ve already got a stimulant, and now you’ve just added another!

    Since that episode, I switched to methylphenidate, which has a lower anxiety profile than dexedrine, and have weened myself off caffeinated drinks. Also, I’m simultaneously taking Strattera, which as an anti-depressant has some benefits for reducing anxiety.

    Long story short: Caffeine has too many side effects, and is too likely to trigger co-morbid anxiety if present, and the attention benefits are far too small, compared to the effects of methylphenidate, dex, or the amphetamine mix in Adderall. It’s not worth it. Some ADHD folks may use caffeine for recreation, but it doesn’t help with the ADHD itself. I would strongly recommend against it (not a doctor, just my personal opinion based on my personal experiences and research).

  10. Thaumas Themelios (Wonderist) says:

    I believe that ADHD is being very much over-diagnosed, and current symptomatic treatments should switch to changes in the environment.
    (Apologies for not providing references)

    Well, *I* believe that ADHD is being very much *under*diagnosed, and current fears over medication are actively detrimental to kids and adults who genuinely have ADHD but are afraid (or have parents who are afraid) to get checked out for effective treatment.

    Myself, I was completely bored and restless throughout the elementary school, and I’m quite convinced that I would have been young today, I’d have been on some medication.

    You say that like it’s a bad thing. If I had been diagnosed as a kid and been given medication, I would have benefited immensely from it, would be in a far better place in my life, and probably wouldn’t have co-morbid anxiety now.

    That said, I do believe there are cases where medication makes sense, but noway near the quoted percentages here.

    Yeah, too bad you don’t have those references handy, because they would tell you the opposite story. Approx. 5% of the population (give or take) has ADHD (meaning they experience real problems from it), and the vast majority are undiagnosed and untreated. This is one of the most treatable conditions around, but unfounded fears of medication and lack of understanding of the condition have gotten in the way of these real people (with real problems) from getting the treatment that may help them (not everyone responds to the meds, but the success rate is high).

    As someone who suffered with undiagnosed ADHD for over thirty years, I can’t understand why anyone would want to put themselves or their children through that kind of torment.

    Anyone reading this now wondering about whether to get themselves or their child checked out: Don’t fall for the fear-based rumour mill. Contact a qualified medical professional (ask your family doctor for a referral) and get checked out properly. It may not be ADHD after all (that’s why you need a proper diagnosis). But if it is ADHD, that’s not a terrible thing. There is effective treatment for most, and even just knowing what you’re dealing with is a huge win. Even if you decide not to go for the meds, at least do so based on the facts, not the anecdotal stories of the rumour mill.

    The costs of undiagnosed/untreated ADHD are huge to those suffering from it, and also to society overall. The wasted potentials and life opportunities can never be regained. Maybe you didn’t put those obstacles up, but why wouldn’t you want to help bring them down? Especially if it’s your child.

    IMHO, looking for treatment for ADHD is no different than looking for eyeglasses for a child who can’t focus enough to read. Why wouldn’t you help, if you knew there was a safe option? Fear?! Is that it? Then get educated on the science, overcome your fear, and learn about the reality of this condition. It is nothing to be afraid of.

  11. ineri says:

    me: “Myself, I was completely bored and restless throughout the elementary school, and I’m quite convinced that I would have been young today, I’d have been on some medication.”

    Thaumas Themelios: “You say that like it’s a bad thing. If I had been diagnosed as a kid and been given medication, I would have benefited immensely from it, would be in a far better place in my life, and probably wouldn’t have co-morbid anxiety now.”

    Yes, I say it as a bad thing, because the proper solution would’ve been to offer schooling where I could have learned in my own pace, not to put me on meds to sit still in class.

    At least where I live, it takes a much more precise evaluation to be diagnosed with Adult ADHD, than ADHD as a kid. I do think that among adults it is probably under diagnosed.

    From your description, it sounds like since you just got your diagnosis, you have also just started on medication. You might (but what do I know) have had another view, if you’d been on methylphenidate or amphetamine for 30 years.

    I’d really like to see attempts to change the environment for kids that show ADHD symptoms before putting them on a drug regime.

  12. ineri “I’d really like to see attempts to change the environment for kids that show ADHD symptoms before putting them on a drug regime.”

    It seems that decision should be based on the individual child’s issues rather than some generalized preference for environmental changes over medication.

  13. BillyJoe says:

    Just a question about the benefits of caffeine: My take was that caffeine helped alertness and performance only when first consumed. However, chronic consumption has no positive effects. In other words, tolerance develops to its effects. Is this wrong?

  14. ineri says:

    micheleinmichigan: “It seems that decision should be based on the individual child’s issues rather than some generalized preference for environmental changes over medication.”

    Since ADHD is very much a diagnosis based on excluding other factors, my point is that we should try harder to try environmental changes before a drug regime. There’s no ‘test’ that says that drugs or environment change will work in an individual case, but I think one should first try environmental changes before deciding to change someone’s dopaminergic network for the rest of their life. So, yes, turns out I do have a ‘generalized preference for environmental changes over medication’, if they work.

  15. Ed Whitney says:

    Follow-up with psychres comment above: there is a new study of this same topic on sleep and “ADHD.”

    Pressman RM, Imber SC. Relationship of Children’s Daytime Behavior Problems With Bedtime Routines/Practices: A Family Context and the Consideration of Faux-ADHD. American Journal of Family Therapy 2011l39(5):404-418.

    Abstract: The study examined the relationship between childhood daytime behavior problems and bedtime routines and practices. Participants were 704 parents of children ages 2–13 who completed a questionnaire in 14 pediatric offices in Providence, Rhode Island. Of particular interest was the highly significant relationship (p-value < 0.0001) between children who bed share or lack regular bedtimes and whose parents are told they should take medicine for behavior or learning problems; and between children who bed share and have physically aggressive behavior toward a parent. Recommendations were made regarding integration of the results in the context of family treatment as well as the consideration of a faux-ADHD.

    They conclude that a child who sleeps in his/her own bed and has regular bedtimes is at lower risk of being diagnosed with ADHD.

  16. “They conclude that a child who sleeps in his/her own bed and has regular bedtimes is at lower risk of being diagnosed with ADHD.”

    Seems that it would be difficult to establish causation here. How do they know that a child with ADHD doesn’t have have a greater tendency to co-sleep or have irregular sleep/bedtimes patterns.

    Or do they not make a claim that the sleep habits are causing the attention/behavior issues?

  17. ineri “but I think one should first try environmental changes before deciding to change someone’s dopaminergic network for the rest of their life.”

    Why do you think that a trial of medication is making the decision to “change someone dopaminergic network” for the rest of their lives.”

    I have never heard that Ritalin is a lifetime commitment like synthroid or the like.

  18. Calli Arcale says:

    Michele:

    I agree that it’s not right to describe a trial of medication as a decision to “change someone dopaminergic network for the rest of their lives”. Ritalin in particular has no evidence of long-term after effects. It’s cleared out of the system remarkably quickly (which is somewhat unfortunate from a therapeutic standpoint, actually, and the reason why extended-release versions are so popular).

    What’s more, many people who take meds as children are able to wean off them later in life, having developing coping strategies that allow them to function. I took Ritalin for years as a child; I do not take it now as an adult. It is not generally a lifetime commitment. It might be, but don’t fret over that now. Worry about the present; you can deal with the future later, and weaning off of methylphenidate is not actually difficult. For all the claims of it being addictive, I had no difficulty weaning off, and I’m doubtful that it’s actually chemically addictive.

    That said, I also agree with ineri that it’s a good idea to try non-drug solutions first. It’s a conservative approach, aiming to minimize impact. If you can relieve the symptoms simply by shifting bedtime, that’s way better than Ritalin. But the flipside, of course, is that the more time spent looking for the right treatment is more time that the child loses in terms of productive education and such. How serious that is probably depends on the severity of the child’s impairment, but once you find the treatment that works, you’ll regret not trying it sooner. It’s not a straightforward thing to balance, but that’s the sort of thing that has to be considered.

  19. Calli Arcale “That said, I also agree with ineri that it’s a good idea to try non-drug solutions first. It’s a conservative approach, aiming to minimize impact. If you can relieve the symptoms simply by shifting bedtime, that’s way better than Ritalin.”

    Thanks for the perspective Calli. I don’t want to suggest that I’m against trying environmental approaches first. My main concern is that ineri idea of offering education where the child can learn at their own pace and doesn’t have to sit still could take quite awhile to negotiate or find in a school system. Should a child who is having severe issues in school and home, meaning daily calls from school, serious delays in learning, intense tantrums at home and no friends in the neighborhood or at school, have to wait for medication help until the parents and school have tried the optimal parenting and schooling techniques?

    Sorry to be argumentative. I have a family member who has really struggled with ADD. His mom was often getting advice that he really didn’t need the medication, that they should do this or that parenting or schooling technique instead. He went off the medication numerous times (at the urging of his father) and had serious legal and school problems as a teen when he was off medication which appeared to be due to impulse control issues.

    I think it’s fine that parents want to explore all the options, be conservative, based on the actual isues the child is having. I’m just uncomfortable with templated answers for imaginary children.

  20. A response for Ed Whitney:

    I have been trained to evaluate ADHD, but I am not experienced in it beyond training. I know enough to know that the field develops regularly, and I am out of step, and it is a complex question.

    However, regarding your question of practice effects and controlled AB/crossover designs:

    Seom executive tasks can be “learned:” subtracting serial 7s, spelling “world” backwards, Trails, etc.

    Many exec tasks cannot be learned as well. Especially the ones they run on computers nowadays – with response suppression (press button if letter T, but only if it follows letter X: the response to press button when seeing T requires additional step of suppressing response, scanning memory for X, then making decision), etc.

    So, lots of these tests will have very low learning effects. Experienced neuropsychologists can judge, or access the data.

    Also, if a study depends on this issue, over-learning can be done: learn to a masterful level at each assessment time before the actual measure is conducted. Study participants won’t like this, but it can be done.

    This makes it hard to judge the evidence, as you say. It can be difficult to track down the practice efect data for a neuropsych test, esp its “learning effect.” The best you might do is to learn abt the exec functioning test given, and consider how much a practice effect reasonably might be involved.

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