ADHD: Unhappy Birthday?

By Neuroskeptic | May 30, 2012 5:44 pm

Earlier this year a major study of almost one million Canadian children found that rates of diagnosed ADHD – as well as use of ADHD medications like Ritalin – were higher in kids born later in the year.

This is strong support for the “immaturity hypothesis” – the idea that some children get a diagnosis of ADHD because they’re younger than their classmates at school, and their relative immaturity is wrongly ascribed to an illness. In British Columbia, where the study happened, the cut-off for school entry is December 31st so those born in January will be a year older than their peers born in December.

Worrying stuff. Clearly this is very important, if true. The authors wrote:

These findings raise concerns about the potential harms of overdiagnosis and overprescribing.

Now a new paper published in the Journal of Attention Disorders rejects the immaturity hypothesis: Is the Diagnosis of ADHD Influenced by Time of Entry to School? The authors say no, it isn’t – but their data don’t actually tell us anything about that.

The esteemed Professor Joseph “Only God Can Judge Me” Biederman and colleagues from Massachusetts General Hospital looked at 562 kids born in August and 529 born in September; the cut-off in the USA is in the summer. Septembers are the oldest in their year, August the youngest.

Of all the children, 55% turned out to have ADHD. There was no difference in rates of ADHD, or the severity of ADHD, between the two groups. Phew! As J-Bo and his East Coast Posse write:

These findings do not support the developmental immaturity hypothesis of ADHD that states that children’s developmental immaturity leads to the inappropriate diagnosis of ADHD. Instead, these findings suggest  that children with clinical thresholds of symptoms of  ADHD are afflicted with this disorder.

But this just doesn’t follow. These results seem to undermine the Canadian data, but they don’t. It’s comparing apples and oranges.

The difference is that Biederman et al diagnosed all of the cases of ADHD themselves, and they are one of the world’s leading ADHD clinical and research teams. All their data show is that being born in August doesn’t fool them into inappropriately diagnosing ADHD.

Sadly, not every child has the privilege of being seen at Mass Gen and having “a comprehensive assessment battery that included structured diagnostic interviews; measures of cognitive, interpersonal, familial, and educational functioning; and examination of patterns of familiality of ADHD.” These lucky kids got a veritable alphabet soup of psychiatric measures, from the K-SADS-E-IV to the SAICA.

The whole claim of the immaturity hypothesis is that children who are young in their year A) don’t actually have more ADHD, but B) tend to get diagnoses when they shouldn’t i.e. after an inadaquate assessment, say by a family doctor, on the advice of a parent or teacher. This study confirms A). It says nothing about B).

At best it shows that younger children aren’t being referred to Mass Gen just because they’re young. But we’re not told who makes those referrals, what their qualifications are, or what systems are in place to filter out inappropriate referrals, so this tells us very little; it also seems that many of the kids included here weren’t referred on suspicion of ADHD at all, but were enrolled in research studies.

But hey, the Journal of Attention Disorders has a Biostatistical and Methodology Editor, Stephen Faraone. Did he approve of this article? Probably – he’s the senior author.

I should stress that none of this proves that “ADHD doesn’t exist” or anything so radical. All it means is that ADHD is sometimes diagnosed badly. Which really shouldn’t surprise anyone, because doctors are human and make mistakes sometimes.

ResearchBlogging.orgBiederman, J., Petty, C., Fried, R., Woodworth, K., & Faraone, S. (2012). Is the Diagnosis of ADHD Influenced by Time of Entry to School? An Examination of Clinical, Familial, and Functional Correlates in Children at Early and Late Entry Points Journal of Attention Disorders DOI: 10.1177/1087054712445061

Morrow, R., Garland, E., Wright, J., Maclure, M., Taylor, S., & Dormuth, C. (2012). Influence of relative age on diagnosis and treatment of attention-deficit/hyperactivity disorder in children Canadian Medical Association Journal, 184 (7), 755-762 DOI: 10.1503/cmaj.111619

  • petrossa

    It shows that ADHD is badly defined. As usual because it's again as almost the whole DSM based on observational behavior studies. Which can't by definition lead to any kind of clearcut definition.

  • Anonymous

    I assume that Joe “I am God” Biederman's study sampled children born in the selected months who were referred for ADHD assessment at his clinic (aka “Heaven” one supposes). Just curious: Is there any data on the expected base rates of a confirmed ADHD diagnosis under such conditions? I mean 55% seems quite inflated, but I don't know. Yet, it is “Heaven” after all!

  • Kees Aleman

    There might be another confounder involved here… Children who are born later in the year (northern hemisphere) usually suffer from more upper airway infections during the following winter that children born early in the year (since the latter are older and stronger). So maybe there is a link between early infancy infections and ADHD… 😉

  • Ivana Fulli MD


    ///All it means is that ADHD is sometimes diagnosed badly. Which really shouldn't surprise anyone, because doctors are human and make mistakes sometimes.///

    Sure! But doctors are also often very busy people with money to spend on a private and/or family life which leave little time to carefully read medical Journals.

    They, poor things, believe in the selfpromotion of geneticians or neuroscientists who wouldn't escape banning from the trade if they published lies in maths or physic Journals-unless they are homeopath that is…

    Plus, some family, teachers, social workers, psychologists ask for precription -sometimes using balckmail like the child will be expelled from the school.

    I already wrote it a couple of time but I had to fight twice very hard to have my son samuel Fulli-Lemaire jump classes at school and that pedagogic measure cured his moving around in calss and interupting the teacher because he was bored to death!

    The second timle I had to homeschool him for three years in a row and without a good friend Pr at Havard (anesthesia) and his wife I do not know if I would have foiund the courage to homeschooled my children when I was accused of being crazy and a danger for their future!

  • ivana Fulli MD

    By the way children born later in the year are younger than children born earlier and -unless they are gifted – they struggle to compete with older children at school.

    L'Ecole Alsacienne- a Paris school for rich children- might have a little tto much pot smoking in pupils to get elitists results at the highschool diploma but they have excellent nursery and primary schools and they make classes according to “born in the first semester or in the second semester for the first years.

    I found that a gorgeaous idea except that my eldest son was born in September and was highly gifted (he took from his academic successful father). it made me save a lot of money.

  • Anonymous

    Again, a great post which shows we should always question WHICH answer we might draw from this or that study. Thanks!

  • Ivana Fulli MD


    I wrote :” by the way” as a lazy shortcut in order to escape looking for your beautiful wording of it.

    The right expresssion in English escaped me . It was not by the way for sure.

    Sorry about that but is is “freudian” and since the second Italian earthquake, as soon as I try to think in English, Italian instead of english substitute French in my brain.

    This not to let you think that i didn't read your post.

  • Neuroskeptic

    Kees: That's a good point, and such seasonal effects are thought to exist. But in the Canadian data it wouldn't explain why there's a jump between Dec and Jan. Both are very cold, so you'd expect them to be similar.

  • Neuroskeptic

    Anonymous: Thanks!

  • Ivana Fulli MD

    Anonymous Neuroskeptic,

    Yesterday and the day before yesterday, I had an interesting experience of what activists with a political agenda are capable of on the Dr Healy “blog reposting” in “Mad In America”

    The point relevant to your post is that one comment :

    Dr D Lightfull on May 31, 2012 at 12:59 pm said:

    ///The disabled rights/labelling movement contributes as much to the rise in drugging and disabling as the APA///

    I truly believe that teachers and social workers are putting psychiatrists under pressure to prescribe and parents under pressure to accept drugs for many children and teenagers in need of:

    1) a better education system
    (the highly gifted get bored into agitation at school and the dyslexic -rare but undiagnosed too often- and the pseudo dyslexic who can't read properly after years of bad schooling in elementary school etc…)

    2)or in need of social or parental measures

    3) better parenting and I am not more against videogames that I am against food but I found ludicrous to let children play games all night long because they compete for points in a game and win failure at school and agitation in the classroom. (for some reasons unknown to me in my little experience the young athlete get to sleep at school but the video “professional so to speak players are often agitated)

    The list is not exhaustive and off course street drugs get some agitated when smoking pot in the school bathrooms -a habit in Italy highschools- to “tolerate ” the school hours just get failure at school.

    And in addition to that, you get the activists who fight in order to have as many large a group as possible and do not try to put in doubt some diagnostic : you become a threat to their influence and knowledge.

    For some activist the good psychaitrist is the one who put his signature on the label an association has decided for a young person -variant put your signature to the label I chose for myself.

  • educator

    This is excellent information. As a tutor I find that there are several conditions that can mimic or cause learning disabilities. You have added one more to my list.

  • Emily

    Good point about what the paper really does mean: of course, they're going to be more consistent within-practice in their diagnostics. Durr.

    I do want to add the caveat that a general physician/pediatrician probably should not diagnose ADHD, which should really involve referral to a specialist, usually a neurologist or psychiatrist, although better would be a developmental pediatrician. It may be that if generalists are making diagnoses, they are likely not (a) taking the required time to do so, and (b) applying the necessary level of expertise and interpretation to it. Perhaps that is where the next study should look: What are correlates of who the diagnostician is?

    Anecdatum: My intensely ADHD son (probably really Tourette's–ADHD/OCD/tics) is always the oldest child in his class, so he doesn't fit that profile of being younger et ergo more immature compared to peers. His issues were manifest by the time he was four. Diagnosis by neurologist and 8-hour batter of neuropsych testing.

  • Neuroskeptic

    Emily: Right. Clearly not everyone who gets a diagnosis of ADHD is just 'immature' – the point is that ADHD is a broad term and covers many different severities. That's the point that Biederman et al miss in their rush to (it seems) defend every single diagnosis of “ADHD”.

  • Ivana Fulli MD

    Allen J. Frances is worth listening to about the overdiagnosis of mental illness and in the increase of diagnostic of ADHD “even when you are careful as a psychiatrist”.

  • Elenore Sebastiene

    During my research I found A fantastic new approach to coping with ADHD. It is by Dutch author, Leonie van Dyk, and is available on Amazon. Hope it helps. Elenore



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About Neuroskeptic

Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.


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