Sharp Brains: Brain Fitness and Cognitive Health News

Neuroplasticity, Brain Fitness and Cognitive Health News

Icon

Why Being Young for Grade Increases Odds of ADHD Diagnosis and Stimulant Medication

ADHD is the most com­mon­ly diag­nosed neu­robe­hav­ioral dis­or­der in chil­dren and sub­stan­tial evi­dence indi­cates that bio­log­i­cal fac­tors play an impor­tant role in its devel­op­ment. For exam­ple, although the exact mech­a­nism by which genet­ic fac­tors con­vey increased risk for ADHD remains unclear, the impor­tance of genet­ic trans­mis­sion has been doc­u­ment­ed in a num­ber of pub­lished stud­ies.

Even though bio­log­i­cal fac­tors are wide­ly regard­ed as impor­tant in the devel­op­ment of ADHD, no med­ical or bio­log­i­cal test is rec­om­mend­ed for rou­tine use when diag­nos­ing ADHD. Instead, like vir­tu­al­ly all psy­chi­atric dis­or­ders, ADHD is defined by a con­stel­la­tion of behav­ioral symp­toms that are gen­er­al­ly report­ed on by a child’s par­ents and teacher. Also, in near­ly all cas­es, it is par­ents’ and/or teach­ers’ con­cerns about a child’s abil­i­ty to focus and reg­u­lar their behav­ior that leads to a child being eval­u­at­ed for ADHD in the first place.

While some chil­dren dis­play suf­fi­cient inat­ten­tive and/or hyper­ac­tive-impul­sive behav­ior to be diag­nosed with ADHD as preschool­ers, it is gen­er­al­ly not before chil­dren enter school that con­cerns relat­ed to atten­tion and hyper­ac­tiv­i­ty arise. This may be espe­cial­ly true for inat­ten­tive symp­toms, as demands for sus­tained atten­tion become much greater when chil­dren start in school. Teach­ers can observe how a child’s abil­i­ty to reg­u­late atten­tion and behav­ior com­pares to an entire class­room — some­thing par­ents typ­i­cal­ly can’t do — and their judge­ments may thus be par­tic­u­lar­ly influ­en­tial in whether a child is eval­u­at­ed for ADHD and diag­nosed with the dis­or­der.

A num­ber of fac­tors may con­tribute to dif­fer­ences in children’s abil­i­ty to focus and reg­u­late their behav­ior when they enter school. One fac­tor cer­tain­ly is ADHD, as chil­dren with the con­di­tion will be observed by teach­ers to be more inat­ten­tive and/or hyper­ac­tive. Anoth­er fac­tor — and one that may be fre­quent­ly over­looked — is their age rel­a­tive to most of their class­mates. This is the issue inves­ti­gat­ed in the stud­ies that are sum­ma­rized below.

Pub­lic school sys­tems have spe­cif­ic dates that a child must be born by to begin kinder­garten. Con­sid­er two chil­dren in a school sys­tem where the cut-off is Decem­ber 31st. Jack is born on Decem­ber 31st, 2007 and would thus be eli­gi­ble to enter kinder­garten dur­ing fall 2012. Com­pared to most of his class­mates who were born as ear­ly as 1/1/2007, he will be rel­a­tive­ly young. On aver­age, in fact, Jack would be about 6 months younger than his peers.

John is born on Jan­u­ary 1st 2008 and would thus be inel­i­gi­ble to enroll in the fall. Instead, he would need to wait until fall 2013 before start­ing kinder­garten. Thus, com­pared to most of his class­mates who could be born as late as 12/31/2008, he will be rel­a­tive­ly old; on aver­age, he would be about 6 months old­er.

Although an age dif­fer­ence of 6 rough­ly may make lit­tle if any dif­fer­ence in the abil­i­ty of old­er chil­dren and ado­les­cents to focus, attend, and reg­u­late their behav­ior, it may make a sub­stan­tial dif­fer­ence in 5 and 6 year-olds. And, dif­fer­ences in near­ly a year — which may be present between the old­est and youngest child in a grade — could be asso­ci­at­ed with large dif­fer­ences on these dimen­sions. This sug­gests that chil­dren rel­a­tive­ly young for grade at the start of school will, on aver­age, be less able to reg­u­late their atten­tion and behav­ior than their class­mates. As a result, young-for-grade chil­dren may be more like­ly to be seen as strug­gling by teach­ers who would con­vey their con­cerns to par­ents. In many cas­es, this may lead par­ents to have their child eval­u­at­ed for ADHD and poten­tial­ly increase the rate of ADHD diag­no­sis and treat­ment in young-for-grade chil­dren. Is there evi­dence that this is the case?

Three recent­ly pub­lished stud­ies pro­vide com­pelling evi­dence that a child’s age rel­a­tive to his or her class­mates is an impor­tant fac­tor in whether they are diag­nosed for ADHD. Results from these stud­ies are sum­ma­rized below.

Study 1

The first study of this issue [Evans, et al., (2010). Mea­sur­ing inap­pro­pri­ate med­ical diag­no­sis and treat­ment in sur­vey data: The case of ADHD among school-age chil­dren. ‚i>Journal of Health Eco­nom­ics, 29, 657–693] used data from the Nation­al Health Inter­view Sur­vey (NHIS), an annu­al sur­vey of house­holds in the US that col­lects data on the extent of ill­ness, dis­ease, and dis­abil­i­ty in the civil­ian pop­u­la­tion. The infor­ma­tion col­lect­ed includes whether sam­ple mem­bers had been diag­nosed with ADHD and pre­scribed stim­u­lant med­ica­tion.

The authors used sur­vey data from 1997 to 2006 and only includ­ed chil­dren from states with a state-wide birth date cut-off for school entry in place when the child was five. Based on this cut-off, which var­ied by state, they exam­ined ADHD diag­no­sis and treat­ment rates for over 35,000 7 to 17 year olds who were born up to 120 days before (i.e., rel­a­tive­ly young for grade) or up to 120 days after (i.e., rel­a­tive­ly old for grade) the state cut-off.

Results indi­cat­ed that 9.7% of young-for-grade chil­dren had been diag­nosed with ADHD com­pared to 7.6% of those rel­a­tive­ly old-for-grade, a dif­fer­ence of approx­i­mate­ly 27%. Rates of stim­u­lant usage were also sig­nif­i­cant­ly dif­fer­ent, 4.5% vs. 4%.

Study 2

A sec­ond study [Elder (2010). The impor­tance of rel­a­tive stan­dards in ADHD diag­no­sis: Evi­dence based on exact birth dates. Jour­nal of Health Eco­nom­ics, 29, 641–656] used data from anoth­er large nation­al data set — the Ear­ly Child­hood Lon­gi­tu­di­nal Study — to exam­ine this issue. The data set ini­tial­ly includ­ed over 18,600 kinder­garten stu­dents from over 1000 kinder­garten pro­grams in the US in the fall of 1998; chil­dren were fol­lowed peri­od­i­cal­ly through 2007 when most were in 8th grade. Avail­able infor­ma­tion includes par­ent and teacher rat­ings of children’s ADHD symp­toms, diag­noses, and stim­u­lant med­ica­tion treat­ments; final results were based on over 11,750 chil­dren.

ADHD diag­no­sis and treat­ment rates were cal­cu­lat­ed for chil­dren born the month before (young-for-grade) and the month after (old-for-grade) the state man­dat­ed cut-off, which was Sep­tem­ber 1 for some states and Decem­ber 1 for oth­ers. For states with the Sep­tem­ber 1 cut-off, 10% of chil­dren born in August were diag­nosed with ADHD com­pared with 4.5% born in Sep­tem­ber. Rates of stim­u­lant med­ica­tion treat­ment were 8.3% vs. 2.5% respec­tive­ly. For states with a Decem­ber 1st cut-off, the diag­no­sis rate for chil­dren born in Novem­ber was 6.8%, more than triple the 1.9% rate for those born in Decem­ber; rates of stim­u­lant treat­ment were 5.0% and 1.5% respec­tive­ly.

The author exam­ined the impact of rel­a­tive age on whether chil­dren were diag­nosed with learn­ing prob­lems oth­er than ADHD, includ­ing devel­op­men­tal delays, autism, dyslex­ia, socio-emo­tion­al behav­ior dis­or­der, or oth­er learn­ing dis­abil­i­ties. For these oth­er learn­ing prob­lems, no rel­a­tive-age effects were found.

The author also demon­strat­ed that school start­ing age had a much stronger effect on teach­ers’ per­cep­tions of children’s ADHD symp­toms than on par­ents’ per­cep­tions. He sug­gests this may be because teach­ers rate children’s behav­ior rel­a­tive to oth­er chil­dren in the class, and rel­a­tive­ly young chil­dren are less able to reg­u­late their atten­tion and behav­ior. Par­ents, in con­trast, may use more absolute stan­dards since they are less above to observe their child in rela­tion to a class­room full of peers.

Study 3

The final study [Mor­row et al., (2012). Influ­ence of rel­a­tive age on diag­no­sis and treat­ment of atten­tion-deficit/hyper­ac­tiv­i­ty dis­or­der in chil­dren.Cana­di­an Med­ical Asso­ci­a­tion Jour­nal, DOI:10.1503/cmaj.11619] exam­ined the asso­ci­a­tion between age-for-grade and ADHD diag­no­sis in a study of over 935,000 youth from British Colum­bia who were 6–12 years of age at any time between Decem­ber 1997 and Novem­ber 2008. Thus, the val­ue of this study is that the sam­ple comes from a dif­fer­ent coun­try and entire­ly dif­fer­ent health care sys­tem than the US.

The cut-off for school entry in British Colum­bia dur­ing this time was Decem­ber 31. Sim­i­lar to the results reviewed above, boys born in Decem­ber were 30% more like­ly to be diag­nosed with ADHD than boys born in Jan­u­ary; girls born in Decem­ber were 70% more like­ly to be diag­nosed with ADHD than girls born in Jan­u­ary. Boys were 41% more like­ly and girls were 77% more like­ly to be treat­ed with med­ica­tion if they were born in Decem­ber rather than Jan­u­ary.

Sum­ma­ry and Impli­ca­tions

Results from 3 inde­pen­dent stud­ies that employed large and rep­re­sen­ta­tive sam­ples indi­cate that chil­dren who are young for their grade are sig­nif­i­cant­ly more like­ly than peers to be diag­nosed with ADHD and to be treat­ed with stim­u­lant med­ica­tion. Based on addi­tion­al analy­ses con­duct­ed in one of these stud­ies, the rel­a­tive age effect is pri­mar­i­ly relat­ed to teach­ers’ per­cep­tions and does not extend to oth­er learn­ing dis­or­ders. These lat­ter two issues were exam­ined in only one of the three stud­ies, how­ev­er, and thus require repli­ca­tion.

Why might being young for grade increase the odds of a child’s being diag­nosed with ADHD? One plau­si­ble expla­na­tion is that focus­ing atten­tion and reg­u­lat­ing behav­ior are abil­i­ties that devel­op over time. At school entry, being up to 12 months younger than class­mates rep­re­sents a sub­stan­tial por­tion of a child’s total age, and these capac­i­ties have had less time to devel­op. As a result, rel­a­tive­ly young chil­dren will gen­er­al­ly be less capa­ble than class­mates of reg­u­lat­ing their atten­tion and behav­ior and more like­ly to be iden­ti­fied by teach­ers as strug­gling on these dimen­sions. They will thus be referred for eval­u­a­tion and diag­nosed with ADHD at high­er rates.

It is impor­tant to note that none of the researchers sug­gest that their data raise ques­tions about the valid­i­ty of ADHD as a ‘real’ dis­or­der with neu­ro­bi­o­log­i­cal under­pin­nings. In my view, using these find­ings to ques­tion the valid­i­ty of the con­di­tion would be high­ly prob­lem­at­ic.

Instead, these find­ings sug­gest that many chil­dren who are young for their grade are diag­nosed not because they have the dis­or­der but because they are devel­op­men­tal­ly less advanced than many of their class­mates. By the same token, chil­dren who are rel­a­tive­ly old for their grade may be under­diag­nosed because their inat­ten­tive­ness and hyper­ac­tiv­i­ty do not seem exces­sive in rela­tion to their younger class­mates. Both out­comes are poten­tial­ly harm­ful and speak to the com­plex­i­ties involved in diag­nos­ing ADHD but not to the valid­i­ty of ADHD as a legit­i­mate dis­or­der.

Results from these stud­ies high­light the impor­tance of care­ful and accu­rate diag­nos­tic eval­u­a­tions. These stud­ies make an impor­tant con­tri­bu­tion to the field by rais­ing aware­ness of the role that rel­a­tive age can play in increas­ing or decreas­ing the risk of receiv­ing an ADHD diag­no­sis. Although there is no easy way to address this com­pli­cat­ing fac­tor, there are sev­er­al steps that may be use­ful to take.

First, clin­i­cians eval­u­at­ing young chil­dren should be espe­cial­ly care­ful when that child is also young rel­a­tive to his class­mates. For chil­dren born close to the cut-off for school entry, spe­cial con­sid­er­a­tion should be giv­en to whether rel­a­tive age may be an impor­tant fac­tor in the child’s behav­ior at school.

Sec­ond, there may be val­ue in nar­row­ing the age ranges used in many of the wide­ly used behav­ior rat­ing scales. Results from these stud­ies sug­gest that there are sig­nif­i­cant nor­ma­tive dif­fer­ences in inat­ten­tive and hyper­ac­tive symp­toms between chil­dren born dur­ing dif­fer­ent months in the same year, let alone in dif­fer­ent years. What is ‘nor­mal’ for a child 6 years and 1 month old dif­fers from what is typ­i­cal for a child 6 years 11 months old.

How­ev­er, behav­ior rat­ing scales gen­er­al­ly have age cat­e­gories that encom­pass mul­ti­ple years. Thus, rather than com­par­ing whether the inat­ten­tive behav­iors a teacher reports for a young 6 year old are exces­sive rel­a­tive to oth­er young 6 year old’s, the child’s score will be deter­mined in rela­tion to a ‘nor­ma­tive group’ that includes chil­dren who are sev­er­al years old­er. As a result, chil­dren at the low end of the age range may be more like­ly to receive ele­vat­ed ADHD symp­tom rat­ing scores than chil­dren at the upper end of the age range. This is very dif­fer­ent from how stan­dard­ized IQ and achieve­ment tests are con­struct­ed, where scores are cal­cu­lat­ed in rela­tion to age groups that span only sev­er­al months.

Third, these find­ings high­light the val­ue of ongo­ing efforts to devel­op a reli­able objec­tive assess­ment mea­sure for ADHD that is not effect­ed by rel­a­tive age effects. As dis­cussed in a pri­or issue of Atten­tion Research Update, Quan­ti­ta­tive EEG (qEEG) may be a help­ful tool in this regard. (See Neurofeedback/ Quan­ti­ta­tive EEG for ADHD diag­no­sis)

Final­ly, the asso­ci­a­tion between rel­a­tive age and risk of diag­no­sis high­lights the impor­tance of sys­tem­at­i­cal­ly reeval­u­at­ing chil­dren each year. As chil­dren devel­op, the impor­tance of rel­a­tive age on the abil­i­ty to reg­u­late atten­tion and behav­ior is like­ly to dimin­ish. For exam­ple, one would expect less dif­fer­ence in the abil­i­ty to sus­tain atten­tion between younger vs. old­er 15 year-olds com­pared to younger vs. old­er 6 year- olds. Thus, if a child was incor­rect­ly diag­nosed with ADHD because he/she was rel­a­tive­ly young at school entry, and thus less capa­ble than peers of reg­u­lat­ing atten­tion and behav­ior, annu­al reeval­u­a­tions should iden­ti­fy this as the child moves into lat­er grades.

Rabiner_David– Dr. David Rabin­er is a child clin­i­cal psy­chol­o­gist and Direc­tor of Under­grad­u­ate Stud­ies in the Depart­ment of Psy­chol­ogy and Neu­ro­science at Duke Uni­ver­sity. He pub­lishes Atten­tion Research Update, an online newslet­ter that helps par­ents, pro­fes­sion­als, and edu­ca­tors keep up with the lat­est research on ADHD, and teach­es the online course  How to Nav­i­gate Con­ven­tion­al and Com­ple­men­tary ADHD Treat­ments for Healthy Brain Devel­op­ment.

Relat­ed arti­cles by Dr. Rabin­er:

Leave a Reply...

Loading Facebook Comments ...

Leave a Reply

Categories: Attention and ADD/ADHD, Cognitive Neuroscience, Education & Lifelong Learning

Tags: , , , , , , , , , , ,

All Slidedecks & Recordings Available — click image below

Search for anything brain-related in our article archives

About SharpBrains

As seen in The New York Times, The Wall Street Journal, BBC News, CNN, Reuters, and more, SharpBrains is an independent market research firm and think tank tracking health and performance applications of brain science.