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ADHD & the brain: Does ADHD treatment improve long-term academic, social and behavioral outcomes?

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The ADHD challenge

The core symp­toms of ADHD fre­quent­ly cause sig­nif­i­cant impair­ment in aca­d­e­m­ic, social and behav­ioral func­tion­ing that adverse­ly impact indi­vid­u­als’ qual­i­ty of life. These symp­toms often per­sist into adult­hood, poten­tial­ly com­pro­mis­ing an indi­vid­u­al’s func­tion­ing over many years. Under­stand­ing how ADHD impacts long-term func­tion­ing, and whether adverse long-term affects are dimin­ished with treat­ment, is thus extreme­ly impor­tant. How­ev­er, despite ample evi­dence that treat­ments such as med­ica­tion and behav­ior ther­a­py yield sub­stan­tial short-term ben­e­fits for most indi­vid­u­als, the impact of treat­ment on longer-term out­comes remains less well-estab­lished. This is an impor­tant gap in the research lit­er­a­ture.

In last mon­th’s issue of Atten­tion Research Update I reviewed a paper that syn­the­sized research on long-term aca­d­e­m­ic out­comes for youth with ADHD. Key find­ings were that aca­d­e­m­ic out­comes were gen­er­al­ly bet­ter for treat­ed vs. untreat­ed youth, but gen­er­al­ly remained sig­nif­i­cant­ly below out­comes attained by youth with­out ADHD.

What about the impact of ADHD and ADHD treat­ment on long-term out­comes in oth­er impor­tant domains such as social and occu­pa­tion­al func­tion­ing, anti­so­cial behav­ior and sub­stance use, dri­ving, and self-esteem? Is there evi­dence that treat­ment helps? Does it help enough to nor­mal­ize out­comes rel­a­tive to those with­out ADHD?

The evidence review

These impor­tant issues were addressed in a paper titled ‘A sys­tem­at­ic review and analy­sis of long-term out­comes in atten­tion deficit hyper­ac­tiv­i­ty dis­or­der: Effects of treat­ment and non-treat­ment’. The paper was pub­lished in 2012 in BMC Med­i­cine.

The authors began by search­ing for rel­e­vant stud­ies pub­lished between 1980 and 2010. All stud­ies com­pared out­comes in par­tic­i­pants with and with­out ADHD or between treat­ed and untreat­ed par­tic­i­pants with ADHD. A total of 351 stud­ies were iden­ti­fied; these includ­ed lon­gi­tu­di­nal stud­ies where indi­vid­u­als were fol­lowed for at least 2 years and cross-sec­tion­al stud­ies where out­comes were mea­sured in groups of par­tic­i­pants at dif­fer­ent ages. Only stud­ies where out­comes were assessed in indi­vid­u­als at least 10-years old were includ­ed. The ages of par­tic­i­pants in these stud­ies extend­ed from chil­dren to old­er adults.

It is impor­tant to note that the stud­ies includ­ed were quite var­ied and have dif­fer­ent method­olog­i­cal strengths and weak­ness­es. And, many were not ‘long-term’ in the sense of fol­low­ing indi­vid­u­als diag­nosed in child­hood to learn how they were doing as young adults; instead, the authors chose to define ‘long-term’ as 2 years or more. These issues are prob­lem­at­ic, but being more restric­tive on the stud­ies includ­ed would have intro­duce dif­fer­ent chal­lenges, e.g., too few stud­ies to ana­lyze. Thus, lim­i­ta­tions in what can be con­clud­ed from the authors work are inevitable and reflect lim­i­ta­tions in the stud­ies they had to draw on.

As not­ed above, 351 stud­ies were includ­ed for analy­sis. Many of these stud­ies includ­ed more than one out­come, so the num­ber of out­comes com­pared exceed­ed this total. Nine dif­fer­ent types of out­comes were exam­ined. These out­comes, and the num­ber of stud­ies in which each was exam­ined, are as fol­lows:

  1. Drug use/addictive behav­ior — 160 stud­ies
  2. Aca­d­e­m­ic out­comes — 119 stud­ies
  3. Anti­so­cial behav­ior — 104 stud­ies
  4. Social func­tion­ing — 98 stud­ies
  5. Occu­pa­tion­al func­tion­ing — 45 stud­ies
  6. Self-esteem — 44 stud­ies
  7. Dri­ving out­comes — 30 stud­ies
  8. Ser­vice use (emer­gency health care, finan­cial assis­tance) — 26 stud­ies
  9. Obe­si­ty — 10 stud­ies

Across all stud­ies, the aver­age length of time for which researchers col­lect­ed data on par­tic­i­pants was 9 years; the range of time for which data was col­lect­ed was 2 years to 40 years. As not­ed above, the stud­ies includ­ed par­tic­i­pants across a wide age-range.

The Results

Com­par­ing results across such dis­parate stud­ies is com­pli­cat­ed, par­tic­u­lar­ly giv­en the vari­ety of out­comes exam­ined and the mea­sures used to exam­ine them. This makes it chal­leng­ing to com­bine results across stud­ies into a sin­gle analy­sis, as is fre­quent­ly done in meta-ana­lyt­ic work. As an alter­na­tive, the authors count­ed how often out­comes were sig­nif­i­cant­ly dif­fer­ent between the groups com­pared in each study, e.g., youth with and with­out ADHD or treat­ed vs. untreat­ed youth with ADHD. They then count­ed the num­ber of times that out­comes were found to be sig­nif­i­cant­ly dif­fer­ent.

For exam­ple, if dri­ving out­comes were com­pared between treat­ed vs. untreat­ed indi­vid­u­als with ADHD in 22 stud­ies, they count­ed how many times the out­come was sig­nif­i­cant­ly bet­ter for treat­ed indi­vid­u­als and how many times there was no sig­nif­i­cant dif­fer­ence.

Out­comes com­par­ing indi­vid­u­als with untreat­ed ADHD to peers

A total of 333 stud­ies com­pared out­comes between untreat­ed par­tic­i­pants with ADHD and con­trols; in many of these stud­ies, mul­ti­ple out­comes were com­pared. Over­all, out­comes for indi­vid­u­als with untreat­ed ADHD were sig­nif­i­cant­ly worse than for com­par­i­son sub­jects approx­i­mate­ly 75% of the time. Infor­ma­tion on whether this var­ied sig­nif­i­cant­ly across dif­fer­ent out­comes, and how much worse out­comes for untreat­ed par­tic­i­pants tend­ed to be, was not pro­vid­ed. Thus, one can’t con­clude much from this sum­ma­ry beyond the fact that indi­vid­u­als with untreat­ed ADHD tend to fare worse over the long-term in mul­ti­ple domains rel­a­tive to those with­out ADHD.

Out­comes with ADHD treat­ment

Treat­ed vs. untreat­ed ADHD was com­pared in 48 stud­ies involv­ing 76 out­comes. For 72% of the out­comes, treat­ed indi­vid­u­als were doing sig­nif­i­cant­ly bet­ter. For the remain­ing 28% of out­comes, treat­ed and untreat­ed indi­vid­u­als gen­er­al­ly did not dif­fer although in rare instances treat­ed indi­vid­u­als were doing worse.

The like­li­hood that treat­ment was linked was linked to bet­ter out­come var­ied con­sid­er­ably across the dif­fer­ent out­comes exam­ined. Treat­ed indi­vid­u­als did bet­ter than untreat­ed indi­vid­u­als for 100% of dri­ving and obe­si­ty out­comes, 90% of self-esteem out­comes, 83% of social func­tion­ing out­comes, 71% of aca­d­e­m­ic out­comes, 67% of drug use out­comes, 50% of anti­so­cial behav­ior out­comes, 50% of ser­vice use out­comes, and 33% of occu­pa­tion­al out­comes.

Thus, for all out­comes except for anti­so­cial behav­ior, ser­vice use, and occu­pa­tion­al func­tion­ing, treat­ed indi­vid­u­als were like­ly to be doing bet­ter. For the lat­ter 3 out­comes, how­ev­er, treat­ed indi­vid­u­als were doing bet­ter between one-third and one-half of the time, and about the same the rest of the time.

It is impor­tant to note that treat­ment var­ied across stud­ies and deter­min­ing the qual­i­ty of treat­ment received was not pos­si­ble. In most stud­ies, par­tic­i­pants received med­ica­tion treat­ment; how­ev­er, non-med­ical treat­ment and treat­ment that com­bined med­ica­tion with oth­er treat­ments were also com­mon. Treat­ment type did not seem to be asso­ci­at­ed with the like­li­hood of bet­ter out­comes but details on this were not pro­vid­ed.

Does treatment normalize outcomes?

The results above sug­gest that ADHD treat­ment is gen­er­al­ly asso­ci­at­ed with bet­ter out­comes. How­ev­er, is treat­ment like­ly to nor­mal­ize out­comes rel­a­tive to indi­vid­u­als with­out ADHD?

This was exam­ined in 42 stud­ies that includ­ed 76 dif­fer­ent out­comes. In most cas­es, out­comes were not nor­mal­ized with treat­ment, mean­ing that indi­vid­u­als with ADHD were doing sig­nif­i­cant­ly worse than com­par­i­son sub­jects. This was found for 58 of the 76 out­comes exam­ined. Thus, equiv­a­lent out­comes between treat­ed par­tic­i­pants and con­trols were found only 18 times.

An impor­tant cau­tion

The above results sug­gest that treat­ment gen­er­al­ly pro­vides long-term ben­e­fits to indi­vid­u­als with ADHD but that it does not typ­i­cal­ly ‘nor­mal­ize’their out­comes. Because the stud­ies con­sid­ered by the authors includ­ed ones from both North Amer­i­ca (US + Cana­da) and Europe, the authors also exam­ined whether treat­ment out­comes var­ied geo­graph­i­cal­ly. It appears that they did.

Specif­i­cal­ly, 86% of out­comes for stud­ies con­duct­ed in Europe were con­sis­tent with treat­ment ben­e­fits com­pared to only 50% of out­comes for North Amer­i­can stud­ies. This may be because North Amer­i­can stud­ies tend­ed to use prospec­tive designs in which indi­vid­u­als with ADHD who did vs. did not receive treat­ment were fol­lowed over time while Euro­pean stud­ies were typ­i­cal­ly ret­ro­spec­tive stud­ies of adults. The for­mer would gen­er­al­ly be con­sid­ered a stronger design so one pos­si­ble inter­pre­ta­tion is that more rig­or­ous stud­ies were less like­ly to doc­u­ment long-term ben­e­fits of ADHD treat­ment.

Summary and implications

The authors’ ambi­tious goal in this paper was to sum­ma­ry exist­ing research on long-term out­comes asso­ci­at­ed with ADHD to address 3 fun­da­men­tal ques­tions:

  1. With­out treat­ment, how often do indi­vid­u­als with ADHD expe­ri­ence sig­nif­i­cant­ly worse out­comes than those with­out the dis­or­der?
  2. Is there evi­dence that ADHD treat­ment improves long-term out­comes? And,
  3. Is there evi­dence that ADHD treat­ment gen­er­al­ly nor­mal­izes out­comes?

To address these ques­tions, they iden­ti­fied over 350 stud­ies con­duct­ed in North Amer­i­ca and Europe in which diverse out­comes were exam­ined over at least a 2‑year peri­od. A wide mix of stud­ies and ages were includ­ed, and detailed infor­ma­tion on the type, dura­tion, and qual­i­ty of ADHD treat­ment was not pro­vid­ed (although this may be exam­ined in sub­se­quent work). While this makes it dif­fi­cult if not impos­si­ble to draw firm con­clu­sions, the pat­tern of results obtained con­verge on the fol­low­ing:

  1. With­out treat­ment, the major­i­ty of indi­vid­u­als with ADHD attain sig­nif­i­cant­ly poor­er out­comes in mul­ti­ple domains rel­a­tive to peers.
  2. Treat­ment gen­er­al­ly results in more pos­i­tive out­comes rel­a­tive to no treat­ment, par­tic­u­lar­ly for dri­ving, obe­si­ty, self-esteem, and social func­tion­ing. The con­sis­tent­ly pos­i­tive results found for obe­si­ty may reflect the appetite sup­press­ing effects of stim­u­lant med­ica­tion. Anti­so­cial behav­ior and occu­pa­tion­al out­comes were less like­ly to show ben­e­fits with treat­ment.
  3. Although ADHD treat­ment gen­er­al­ly results in bet­ter long-term out­comes rel­a­tive to no treat­ment, even with treat­ment out­comes are typ­i­cal­ly not nor­mal­ized. Thus, most indi­vid­u­als with ADHD con­tin­ue to be doing less well in mul­ti­ple domains than their peers.

As not­ed above, lim­i­ta­tions in the research base that the authors had to drawn on lim­its any con­clu­sions that can be made about the long-term impact of ADHD treat­ment. In addi­tion, the authors did not con­sid­er how dif­fer­ent types of treat­ment or dura­tion of treat­ment effect­ed treat­ment out­comes, although they indi­cate plans to do this in sub­se­quent work. They also did not dis­cuss the mag­ni­tude of treat­ment effects, which makes it dif­fi­cult to know how often sta­tis­ti­cal­ly sig­nif­i­cant dif­fer­ences between treat­ed and untreat­ed indi­vid­u­als were like­ly to be clin­i­cal­ly mean­ing­ful.

Thus, despite the sig­nif­i­cant effort rep­re­sent­ed by this paper, impor­tant ques­tions remain about the long-term impact of ADHD treat­ment. In fact, the authors con­clude their paper by stat­ing that the “…ques­tion remains as to whether the short-term ben­e­fits demon­strat­ed by short-term drug or non-phar­ma­co­log­i­cal treat­ment stud­ies trans­late into long-term out­comes.”

Hope­ful­ly, sub­se­quent work by these authors and oth­ers in the field will soon pro­vide a more defin­i­tive answer to this basic and impor­tant ques­tion.

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.

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