Attention- deficit hy per ac tiv ity dis or der (ADHD) is con -

Transcription

1 Attention-Deficit Hyperactivity Disorder in Manitoba Children: Medical Diagnosis and Psychostimulant Treatment Rates Marni D Brownell, PhD 1, Ma rina S Yo gen dran, MSc 2 Ob jec tive: To de scribe phy si cians di ag no sis rates for attention- deficit hy per ac tiv ity dis or der (ADHD) for chil dren in the prov - ince of Mani toba and to de scribe the rate of psy chostimu lant medi ca tion use by these chil dren. Meth ods: This de scrip tive study re viewed the com put er ized ad min is tra tive rec ords of phy si cian vis its and pre scrip tions dis - pensed to ex am ine a population- based, cross- sectional co hort of chil dren di ag nosed with ADHD or pre scribed stimu lant medica - tion, or both. We found 4787 children with a di ag no sis of ADHD over a 24- month period or a pre scrip tion for stimu lant medi ca tion over a 12- month pe riod, or both. Rates were cal cu lated by age, sex, re gion of resi dence, neigh bour hood in come level, and phy si cian spe cialty. Re sults: Among Mani toba chil dren, 1.52% re ceived a medi cal di ag no sis of ADHD and 0.89% re ceived stimu lant medi ca tion. Re - gion ally, di ag no sis rates for ADHD var ied al most 4- fold, and over 8- fold for medi ca tions pre scribed. Ur ban are as had higher rates than did ru ral areas, re gard less of phy si cian spe cialty. Di ag no sis and pre scrip tion rates var ied ac cord ing to phy si cian spe - cialty, with the highest rates found among pe dia tri cians. An income gradient was evi dent in ru ral ar eas, with rates of ADHD diag - no sis and medi ca tion pre scribed in creas ing with in creased neigh bour hood in come level. Con clu sions: The pat tern of re gional variation found in this study sug gests that the di ag no sis and treat ment of ADHD in Mani - toba are in flu enced strongly by the prac tice styles of lo cal phy si cians. (Can J Psy chia try 2001;46: ) Key Words: attention-deficit hyperactivity disorder, psychostimulants, regional variations, socioeconomic status, population-based rates Attention- deficit hy per ac tiv ity dis or der (ADHD) is con - sid ered to be the most com mon mental dis or der of child - hood (1 3), and yet it is also one of the most con tro ver sial con di tions of child hood (4). Psy chostimu lant medi ca tion, the most ef fec tive treat ment for ADHD, is no less con tro ver sial. Re cent years have seen growing public con cern, fu elled by me dia re ports, that ADHD is over di ag nosed and over treated with medi ca tions (5 7). Some groups have gone so far as to claim that the dis or der does not even exist, re fer ring to stimu - lant medi ca tions as chemi cal straight- jackets (8). Sta tis tics in di cat ing a dra matic in crease in the pro duc tion and use of psy chostimu lants, par ticu larly meth ylpheni date (MPH), have con trib uted to the per cep tion that ADHD is over di ag nosed and over treated. Since the early 1970s, the use of medi ca tion to treat chil dren with ADHD has in creased stead ily in the US, with at least 2- fold in creases every 4 to 7 years (9). More re cent US data in di cate that be tween 1990 and 1995 there was a 2.5- fold in crease in the use of MPH to treat ADHD (10). Ca na dian data show rela tively little change in the con sump tion of MPH be tween 1983 and 1990, with dra matic in creases 3- fold be tween 1993 and 1996 in the 1990s (11). Ri ta lin sales in creased 4.6- fold be tween 1990 and 1996 (12). An in crease in MPH con sump tion, how ever, does not nec es sar ily sig nify mis use or over use. The ef fi cacy of medi ca tion, par ticu larly MPH, for treat ing symp toms of ADHD has been dem on strated in both short- term (13,14) and longer- term (15) studies. Manuscript received February 2000, revised, and accepted January Presented at the American Psychological Society Conference, May 1998, Washington, DC. 1 Research Associate, Manitoba Centre for Health Policy and Evaluation; Assistant Professor, Department of Community Health Sciences, Faculty of Medicine, University of Manitoba, Winnipeg, Manitoba. 2 Systems Analyst, Manitoba Centre for Health Pol icy and Evaluation, Win - nipeg, Manitoba. Address for correspondence: Dr MD Brownell, Manitoba Centre for Health Policy and Evaluation, Department of Community Health Sciences, Fac ulty of Medicine, University of Manitoba, St Boniface General Hospital Re - search Centre, Room 2008, 351 Ta ché Avenue, Winnipeg, MB R2H 2A6 brownl@cpe.umanitoba.ca In Mani toba, the use of MPH has been care fully tracked since 1990 by the pro vin cial li cens ing body for phy si cians. Be - tween 1990 and 1997, pre scrip tions for MPH in creased dra - mati cally, with a 497% in crease in the mil li grams dis pensed and a 439% in crease in the number of pre scrip tions writ - ten(16). Al though this startling in crease would seem to sup - port the no tion that MPH is over pre scribed in Mani toba, Zito and oth ers caution that count ing pre scrip tions rather than per - sons over es ti mates drug preva lence, in some cases more than 6- fold (17). Population- based analy ses that count cases rather than pre scrip tions pro vide a more re al is tic es ti mate of the preva lence of stimu lant use (18). Can J Psychiatry, Vol 46, April

2 April 2001 ADHD in Manitoba Children 265 This study uses a population- based in for ma tion sys tem to ex - am ine stimu lant medi ca tion use by chil dren in Mani toba. The sys tem in cludes ad min is tra tive claims both for pre scrip tions dis pensed and for phy si cian serv ices for the en tire Mani toba popu la tion. Us ing these data, we seek an swers to the fol low - ing ques tions: What is the rate of ADHD di ag no sis by physi - cians in the province of Mani toba? Who is mak ing these di ag no ses gen eral prac ti tio ners, pe dia tri cians, or psy chia - trists? For those di ag nosed with ADHD, what fac tors de ter - mine the use of stimu lant medi ca tion as treat ment? What can re gional varia tions in di ag no sis rates or pre scrib ing pat terns tell us about pos si ble un der- or over di ag nos ing or pre scrib ing? Methods Study Design This is a de scrip tive study ex am in ing a population- based, cross- sectional co hort of chil dren di ag nosed with ADHD within a 24- month pe riod or pre scribed psy chostimu lant medi ca tion over a 12- month pe riod, or both. Data Sources Us ing com put er ized ad min is tra tive da ta bases main tained by the Mani toba Health Re search Data Re posi tory, we com - bined population- based data on the di ag no sis and treat ment of ADHD. These data con tain anony mous encounter- based rec ords of in di vidu als in ter ac tions with the pro vin cial health care system. Uni ver sal in sur ance cov er age and com pre hen - sive re port ing of serv ices en sures virtually com plete and ac - cu rate in for ma tion on health care use by the popu la tion of Mani toba. The va lid ity and re li abil ity of these data for use in health care re search have been ex ten sively stud ied (19 24). Phy si cian Claims Files. Phy si cian serv ices for Mani toba resi - dents are cov ered un der the Mani toba Health Serv ices In sur - ance Plan (MHSIP). Fee- for- service phy si cians sub mit claims to MHSIP for re im burse ment, whereas sala ried physi - cians sub mit claims for record- keeping pur poses. Thus, vis its to al most all phy si cians in the prov ince are cap tured, but serv - ices for cer tain ses sional phy si cians and emergency- room doc tors may not be cap tured. Claims con tain a unique nu - meric pa tient iden ti fier, a nu meric fam ily iden ti fier, and codes uniquely iden ti fy ing the phy si cian and the phy si cian spe cialty. Claims also con tain a sin gle ICD- 9- CM di ag no sis code, coded to the level of the third digit. Drug Pro gram In for ma tion Net work (DPIN). The DPIN is an ad min is tra tive claims da ta base con tain ing rec ords of pre - scrip tions dis pensed to Mani toba resi dents for out- ofhospital use. All community- based phar ma cies in the prov - ince are re quired to sub mit com put er ized rec ords of phar ma - ceu ti cals dis pensed at the time of dis pen sa tion. Also in cluded in the DPIN da ta base are most of the pre scrip tions dis pensed by hos pi tals for out pa tient use. Claims in this da ta base con - tain a unique nu meric pa tient iden ti fier, the drug iden ti fi ca tion number (DIN), ge neric drug names, and the date and quan tity dispensed. Popu la tion Reg is try. Popu la tion de nomi na tors for cal cu lat - ing rates were taken from the reg is try of all Mani to bans eli gi - ble for cov er age un der the MHSIP. We in cluded Mani toba resi dents up to age 19 years. For this study, we used the popu - la tion census of De cem ber 31, We used in for ma tion on av er age neigh bour hood in come level de vel oped from 1991 public- use cen sus data (25,26) as a meas ure of so cio eco - nomic status (SES). Popu la tion and Study Period Our study pe riod was fis cal year (April 1, 1995 to March 31, 1996). On De cem ber 31, 1995, there were chil dren resi dent in the prov ince. Of these children, 92% (Note) had at least 1 re corded visit to a phy si cian in the 1995 fis cal year, with 4.4% of the visits re cord ing a mental health (ICD- 9- CM 290.xx- 319.xx) di ag no sis. Of chil dren resi dent in Mani toba dur ing the study pe riod, 3106 had a re corded di - ag no sis of ADHD (ICD- 9- CM 314.xx) on the phy si cian claims file. An ad di tional 1141 (nonover lap ping) chil dren had an ADHD claim in the pre ced ing 12- month pe riod. Given the per sis tent nature of ADHD (1,27), these chil dren were in - cluded in the analy ses, bringing the total number of claims from the medi cal file to During the study pe riod, 2814 chil dren had at least 1 pre scrip tion claim for stimu lant medi - ca tion (that is, MPH, dex tro am pheta mine, and pe mo line). Of these, 2246 (79.8%) could be linked to an ADHD di ag no sis in the phy si cian claims files for fis cal year or , whereas 568 (20.2%) did not have a cor re spond - ing ADHD di ag no sis in the phy si cian claims files. There were 28 chil dren with a pre scrip tion claim that could not be linked ei ther to an ADHD di ag no sis on the phy si cian rec ord or to a phy si cian visit for any con di tion. There fore, these chil dren were dropped from the analyses. Claims were searched for a cor re spond ing di ag no sis of nar co lepsy, which can also be treated with psy chostimu lants, but none was found. The re - main ing 540 chil dren with a pre scrip tion claim, but no cor re - spond ing ADHD claim on the phy si cian file, were re tained for analyses. Of these re main ing 540 non link ing claims, 159 (29%) had an ADHD claim on the phy si cian file at some point in the 10 years prior to the study pe riod, and 49 (9.1%) could be linked to a di ag no sis of con duct dis or der (CD). The total study popu la tion was 4787 chil dren. Sta tis ti cal Analyses For the analyses, the study popu la tion was di vided into cate - go ries ac cord ing to sex, age at first visit of the study year, re - gion of resi dence (de ter mined by postal and mu nici pal codes), and neigh bour hood in come level (see Data Sources sec tion above. The popu la tion was cate go rized into quin tiles sepa rately for ur ban and ru ral ar eas). Cases were also catego - rized ac cord ing to 3 phy si cian spe cial ties: gen eral prac ti tio - ners, pe dia tri cians, and psy chia trists. Chil dren who re ceived a di ag no sis of ADHD from more than 1 phy si cian specialty

3 266 The Canadian Journal of Psychiatry Vol 46, No 3 Table 1. Rate of medical diagnosis of ADHD and psychostimulant medication prescribed per 1000 population, by age and sex 0 3 years (99%CI) 4 6 years (99%CI) 7 9 years (99%CI) years (99%CI) 14 years and over (99%CI) To tal (99%CI) All ADHD di ag no sis rate 4.8 ( ) 16.6 ( ) 29.1 ( ) 22.4 ( ) 8.2 ( ) 15.2 ( ) Psy chostimu lant rate 0.4 ( ) 7.6 ( ) 19.9 ( ) 15.1 ( ) 4.5 ( ) 8.9 ( ) Male children ADHD di ag no sis rate 7.0 ( ) 25.4 ( ) 46.7 ( ) 36.3 ( ) 12.5 ( ) 24.1 ( ) Psy chostimu lant rate 0.7 ( ) 12.1 ( ) 32.6 ( ) 25.1 ( ) 6.8 ( ) 14.5 ( ) Female children ADHD di ag no sis rate 2.6 ( ) 7.3 ( ) 10.6 ( ) 7.6 ( ) 3.6 ( ) 6.0 ( ) Psy chostimu lant rate 0.1 ( ) 2.8 ( ) 6.7 ( ) 4.5 ( ) 1.9 ( ) 3.0 ( ) cate gory were as signed to the cate gory of great est spe ciali za - tion, ac cord ing to the fol low ing de scend ing or der of spe ciali - za tion: psy chia trist, pe dia tri cian, gen eral prac ti tio ner. For com pari sons of rates across re gions, in come quintiles, and phy si cian spe cialty, rates were age- and sexstandardized, using the direct method of stan dardi za tion. Due to empty cells, larger age cate go ri za tions (0 to 9 years and 10 to 19 years) were used for stan dardi za tion. Sta tis ti cal com - pari son tests of all rates were done us ing t-test methodology de vel oped by Carriere and Roos (28). We im ple mented a Bon fer roni cor rec tion fac tor us ing 99% con fi dence in ter vals (CIs) when test ing for sta tis ti cal sig nifi cance be tween rates. Lo gis tic re gres sion analy sis was per formed to de ter mine which vari ables were re lated to psy chostimu lant pre scrip - tions for those chil dren given a di ag no sis of ADHD. All lev - els of all vari ables were en tered into the model, and odds ra tios (ORs) and CIs were cal cu lated at a 0.05 level of sig nifi - cance for the full model. Results Over all, 1.52% of Mani toba chil dren re ceived a medi cal di - ag no sis of ADHD, and 0.89% re ceived stimu lant medi ca tion (Ta ble 1). Of those chil dren who re ceived a di ag no sis of ADHD, 58.6% (8.9/15.2) were treated with medi ca tion. Ta - ble 1 shows the rates for medi cal di ag no sis of ADHD and stimu lant medi ca tion pre scrip tion, by age and sex. The peak age of di ag no sis and medi ca tion for both male and fe male chil dren was the 7- to 9- year- old group. The low est di ag no sis and pre scrip tion rates oc curred for the young est age group, with less than 10% (0.4/4.8) of the 0- to 3- year- old chil dren di ag nosed with ADHD re ceiv ing pre scrip tions. At each age cate gory, male chil dren are much more likely than are fe male chil dren to be di ag nosed with ADHD and to re ceive stimu lant medi ca tion. For ADHD di ag no sis, the overall ra tio of male to fe male chil dren was 4.0:1, with the small est sex dif fer ence oc cur ring at the young est age level (2.7:1) and the widest gap oc cur ring at the 10- to 13- year- old age level (4.8:1). The over all rate of medi ca tion use was al most 5 times higher in male chil dren than it was in fe male chil den, with the great est ra tio oc cur ring at the youngest age group (7.0:1). Of the male chil dren di ag nosed with ADHD, 60% (14.5/24.1) were treated with stimu lants, com pared with 50% (3.0/6.0) of the fe male chil dren. Di ag no sis of ADHD and treat ment with medi ca tions dif fered ac cord ing to the spe cialty of the phy si cian seen. For Mani toba chil dren aged 0 to 19 years and di ag nosed with ADHD, al - most 58% (8.8/15.2) ob tained this di ag no sis from a pe dia tri - cian, 27% (4.1/15.2) from a gen eral prac ti tio ner, and over 14% (2.2/15.2) from a psy chia trist (Table 2). For each age cate gory, the ADHD di ag no sis and psy chostimu lant pre - scrip tion rates were higher for pe dia tri cians than for the other 2 phy si cian groups. For all but the oldest age group, the diag - no sis and pre scrip tion rates were higher for gen eral prac ti tio - ners than for psy chia trists. Mani toba can be di vided into 14 sepa rate health re gions. Of these, 11 are based on the re gional health authori ties es tab - lished for north ern and ru ral health serv ices, and 3 ar eas lie within the city of Win ni peg. We ran our analy ses by these 14 re gions, as well as by 4 broader re gional cate go ries: Win ni - peg (child popu la tion ), Bran don and sur round ing area (child popu la tion ), north ern (re gions of the prov - ince above the 53rd par al lel with a child popu la tion of ), and other (south ern ru ral ar eas with a child popu la - tion of ). Within the larger re gional cate go ries, there was an al most 4- fold varia tion in di ag no sis of ADHD (Ta ble 3), with those chil dren in the north ern re gion least likely to re - ceive di ag no sis (6.3 per 1000) and those chil dren liv ing in Bran don the most likely to re ceive di ag no sis (25.0 per 1000). The rates for medi ca tion across re gions vary more than 8- fold, with the north ern re gion having the low est rate (2.2 per 1000) and the Bran don re gion having the high est rate (17.8 per 1000). For those chil dren di ag nosed with ADHD, the per - cent age on medi ca tion was lower for chil dren from the north (2.2/6.3 = 34.9%) than for any other re gion of the prov ince,

4 April 2001 ADHD in Manitoba Children 267 Table 2. Rate of medical diagnosis of ADHD and psychostimulant medication prescribed per 1000 population, by age and physician specialty 0 3 years (99%CI) 4 6 years (99%CI) 7 9 years (99%CI) years (99%CI) 14 years and over (99%CI) To tal (99%CI) Psychiatrists ADHD di ag no sis rate 0.1 ( ) 1.3 ( ) 3.6 ( ) 3.9 ( ) 2.3 ( ) 2.2 ( ) Psy chostimu lant rate ( ) 2.4 ( ) 2.2 ( ) 1.0 ( ) 1.2 ( ) Pediatricians ADHD di ag no sis rate 2.9 ( ) 11.1 ( ) 18.3 ( ) 12.2 ( ) 3.4 ( ) 8.8 ( ) Psy chostimu lant rate 0.3 ( ) 5.3 ( ) 13.0 (1 14.4) 9.0 ( ) 2.1 ( ) 5.5 ( ) General Practitioners ADHD di ag no sis rate ( ) 4.1 ( ) 7.0 ( ) 6.1 ( ) 2.4 ( ) 4.1 ( ) Psy chostimu lant rate 0.1 ( ) 1.5 ( ) 4.4 ( ) 3.9 ( ) 1.4 (1.1 ) 2.2 ( ) Overall Table 3. Rate of medical diagnosis of ADHD and psychostimulant medication prescribed per 1000 population 0 19 years, by region and physician specialty Win ni peg (99%CI) Bran don (99%CI) North ern (99%CI) Other (99%CI) ADHD di ag no sis rate 19.1 ( ) 25.0 ( ) 6.3 ( ) 10.4 ( ) Psy chostimu lant rate 11.5 ( ) 17.8 ( ) 2.2 ( ) 5.6 ( ) Psychiatrists ADHD di ag no sis rate 3.5 ( ) 0.5 ( ) 0.6 ( ) 1.0 ( ) Psy chostimu lant rate 2.0 ( ) 0.4 ( ) 0.2 ( ) 0.4 ( ) Pediatricians ADHD di ag no sis rate 11.9 ( ) 15.7 ( ) 1.9 ( ) 5.1( ) Psy chostimu lant rate 7.4 ( ) 11.5 ( ) 0.9 ( ) 3.0 ( ) General Practitioners ADHD di ag no sis rate 3.7 ( ) 8.8 ( ) 3.8 ( ) 4.2 ( ) Psy chostimu lant rate 2.0 ( 2.4) 6.0 ( ) 1.1 ( ) 2.1 ( 2.5) and the per cent age for chil dren from Bran don was higher than for any other re gion in the prov ince (17.8/25.0 = 71.2%). When we looked at the 14 dif fer ent re gions (not shown), the per cent age of those who were di ag nosed and treated with medi ca tion ranged from less than 20% to 73%. A gen eral prac ti tio ner was most likely to di ag nose chil dren from the north ern re gion (3.8/1000), whereas pe dia tri cians were most likely to make the di ag no sis of ADHD for chil dren liv ing in all other re gions of the prov ince (11.9/1000 for Win - ni peg resi dents, 15.7/1000 for Bran don resi dents, and 5.1/1000 for resi dents of other re gions) (Ta ble 3). Re gional varia tion was evi dent in di ag no sis and pre scrip tion rates, re - gard less of the type of prac ti tio ner, with greater variation across re gions for pe dia tri cians and psy chia trists than for gen eral prac ti tio ners. For those chil dren liv ing in ur ban ar eas, there was little differ - ence in rates of di ag no sis across neigh bour hood in come quin tiles, al though there was a greater ten dency for an in - crease in pre scrip tion rate as in come quin tiles in creased: 9.6/1000 chil dren from the lowest in come level re ceived medi ca tion com pared with 11.1/1000 for chil dren from the high est 2 ur ban in come lev els (Ta ble 4). The in come gra di - ents were far more pro nounced for those chil dren living in ru - ral ar eas. Com pared with those in the low est in come group, those in the highest in come quintile had higher rates of ADHD di ag no sis (13.1/1000 com pared with 6.3/1000), higher rates of medi ca tions pre scribed (7.8/1000 com pared with 1.9/1000), and higher per cent ages of di ag nosed chil dren pre scribed medi ca tions (7.8/13.1 = 59.5% com pared with 1.9/6.3 = 30.2%). For those di ag nosed with ADHD by a psy chia trist, there was a slight gra di ent in di ag no sis rates, with those chil dren from the highest 2 ur ban in come lev els hav ing higher rates of diag - no sis than those chil dren from the low est 2 neigh bour hood in - come lev els (Ta ble 4). For pre scrip tion rates, those from the

5 268 The Canadian Journal of Psychiatry Vol 46, No 3 Table 4. Rate of medical diagnosis of ADHD and psychostimulant medication prescribed per 1000 population 0 19 years, by urban and rural neighbourhood income quintile and physician specialty In come Quintiles* Ur ban Ru ral Q1 Q2 Q3 Q4 Q5 Q1 Q2 Q3 Q4 Q5 Overall ADHD di a gno sis rate 17.5 ( ) 16.4 ( ) 18.4 ( ) 18.3 ( ) 17.5 ( ) 6.3 ( ) 7.3 ( ) 8.1 ( ) 11.1 ( ) 13.1 ( ) Psy chostimu lant rate 9.6 ( ) 10.0 ( ) 10.7 ( ) 11.1 ( ) 11.1 ( ) 1.9 ( ) 3.4 ( ) 4.6 ( ) 6.6 ( ) 7.8 ( ) Psychiatrists ADHD di agno sis rate 2.2 ( ) ( ) 2.9 ( ) 3.4 ( ) 3.5 ( ) 0.7 ( ) 0.5 ( ) 0.8 ( ) 0.8 ( ) 1.9 ( ) Psy chostimu lant rate 1.3 ( ) 1.0 ( ) 1.5 ( ) ( ) 2.1 ( ) 0.2 ( ) 0.1 ( ) 0.5 ( ) 0.3 ( ) 0.9 (0.5 ) Pediatricians ADHD di agno sis rate 10.7 ( ) 9.6 ( ) 10.7 ( ) 11.1 ( ) 10.8 ( ) 2.6 ( 3.6) 2.8 ( ) 3.6 ( ) 6.2 ( ) 8.0 ( ) Psy chostimu lant rate 6.0 ( ) 6.4 ( ) 6.5 ( ) 7.2 ( ) 7.1 ( ) 0.9 ( ) 1.4 ( ) 2.2 ( ) 4.0 ( ) 5.1 ( ) General Practitioners ADHD di ag no sis rate 4.6 ( ) 4.9 ( ) 4.8 ( ) 3.8 ( ) 3.2 ( ) 3.0 ( ) 4.0 ( ) 3.7 ( ) 4.2 ( ) 3.2 ( ) Psy chostimu lant rate 2.3 ( ) 2.6 ( ) 2.7 ( ) 2.1 ( ) ( ) 0.8 ( ) ( ) 2.0 ( ) 2.3 ( ) ( ) a Quin tile 1 rep re sents those from the poor est in come neigh bour hoods; quin tile 5 rep re sents those from the wealthi est in come neigh bour hoods. low est 2 ur ban in come lev els had lower pre scrip tion rates than did those from the highest level. No gradient emerged for chil dren living in ru ral ar eas, al though chil dren from the high - est in come group who saw psy chia trists were more likely to be di ag nosed and to re ceive medi ca tions than were chil dren from the other in come lev els. No clear pat terns emerged for ur ban chil dren di ag nosed by pe dia tri cians, whereas with ru ral chil dren, in come quintile was re lated both to di ag no sis and to medi ca tion rates. As in come in creased, so did the rate of both ADHD di ag no sis and medi ca tion use. Chil dren from ur ban ar eas were less likely to be di ag nosed by a gen eral prac ti tio - ner if they were from the high est in come level. Simi larly, for ur ban chil dren seeing gen eral prac ti tio ners, medi ca tion use was low est in the high est in come group. The re verse was true for ru ral chil dren, with the lowest medi ca tion use found for the lowest in come group. The lo gis tic re gres sion analy sis al lowed us to de ter mine which vari ables pre dicted medi ca tion use once a child was di - ag nosed with ADHD (Ta ble 5): male chil dren were al most 1.5 times more likely to be pre scribed medi ca tion than were fe male chil dren. Chil dren aged 4 to 6 years were less likely, and chil dren aged 10 to 13 years more likely, to be pre scribed medi ca tions once di ag nosed than were chil dren aged 7 to 9 years (there were too few chil dren in the 0- to 3- year category to en ter into the re gres sion model). Pe dia tri cians were 1.45 times more likely to pre scribe medi ca tion to chil dren diag - nosed with ADHD than were psy chia trists, whereas gen eral prac ti tio ners were no more or less likely to pre scribe medi ca - tions to chil dren di ag nosed with ADHD than were psy chia - trists. Once di ag nosed with ADHD, chil dren liv ing in Bran don were 1.7 times more likely to re ceive medi ca tion than were chil dren living in Win ni peg, whereas those diag - nosed with ADHD and liv ing in the north ern re gion were much less likely to re ceive medi ca tions than were those in Win ni peg. Ur ban chil dren di ag nosed with ADHD were more likely to re ceive medi ca tion if they lived in neigh bour hoods with the sec ond lowest or high est in come lev els, whereas, for ru ral chil dren di ag nosed with ADHD, the like li hood of re - ceiv ing medi ca tion in creased with each in crease of in come level. Chil dren with the high est in come lev els who were diag - nosed with ADHD and liv ing in ru ral ar eas were 3.6 times more likely to re ceive medi ca tion than were those from the low est in come ar eas. Discussion The age and sex pat tern of re sults found in our study is simi lar to that found in the lit era ture on ADHD and stimu lant medi ca - tion use. There is gen eral agree ment that the preva lence of

6 April 2001 ADHD in Manitoba Children 269 Table 5. Predictors of psychostimulant prescription for children diagnosed with ADHD Response Variables Sex Age Fe male OR (95% CI) Male (1.248, 1.687); P < to (0.518, 0.725); P < to 9 10 to (1.300, 1.755); P < (0.742, 1.085) Physician specialty Region Psy chia trist Pe dia tri cian (1.217, 1.736); P < 0.05 Gen eral Practitioners (0.851, 1.266) Win ni peg Bran don (1.304, 2.235); P < 0.05 North (0.314, 0.628); P < 0.05 Other (0.786, 1.174) Urban Income Quintiles a Q1 Q (1.006, 1.552); P < 0.05 Q (0.882, 1.340) Q (0.998, 1.509) Q (1.132, 1.720); P < 0.05 Rural Income Quintiles a Q1 Q (1.330, 3.559); P < 0.05 Q (1.961, 5.182); P < 0.05 Q (2.164, 5.438); P < 0.05 Q (2.289, 5.593); P < 0.05 a For the re gres sion model all ru ral and ur ban in come quin tiles were en tered into the model to gether with ur ban Q1 as the. For il lus tra tive pur poses we have in - cluded in this ta ble re sults of an analysis ex am in ing ru ral and ur ban in come levels sepa rately, ad just ing only for age and sex. ADHD tends to peak prior to ado les cence and de cline there - af ter, with higher rates for boys than for girls (29). Al though clini cal stud ies find sex ra tios in the or der of 9 to 1, our sex ra - tio is more simi lar to the 4- to-1 ra tios found in epi de mi ol ogi - cal studies (30). Once di ag nosed with ADHD, boys are more likely than girls to be treated with stimu lant medi ca tion, per - haps be cause their be hav iour is more dis rup tive (30). The low est rate of stimu lant medi ca tion found for both male and fe male chil dren was for those in the group aged 0 to 3 years. Less than 10% of all chil dren in this age group di ag nosed with ADHD were pre scribed stimu lant medi ca - tion. This re sult is in stark con trast to a re cent study from Michi gan which found that 57% of those chil dren in this age group di ag nosed with ADHD were pre scribed psy cho tropic medi ca tion (31). Given the po ten tial dif fi culty of di ag nos ing ADHD in younger chil dren (27) and the dearth of con trolled stud ies on the safety and ef fi cacy of stimu lant use in pre - school ers (32), the re sults of this study sug gest that Mani toba phy si cians are adopting a more cau tious ap proach to the phar - ma col ogi cal treat ment of this dis or der in very young chil dren. Chil dren in Mani toba are more likely to be di ag nosed and treated by a pe dia tri cian than by a gen eral prac ti tio ner or psy - chia trist. In our study pe riod, al most 33% of chil dren diag - nosed with men tal dis or ders (ICD- 9- CM ) by pe dia tri cians were di ag nosed with ADHD, com pared with 20% di ag nosed by psy chia trists and 12% di ag nosed by gen - eral prac ti tio ners. Pe dia tri cians are also more likely to pre - scribe medi ca tion once a di ag no sis of ADHD has been made. It is per haps sur pris ing that the pro por tion of di ag nosed chil - dren re ceiv ing medi ca tion is lower for psy chia trists than for pe dia tri cians, given that those chil dren see ing psy chia trists may be more likely to have more com plex and se vere symp to - mol ogy than those seeing other prac ti tio ners (33). It is possi - ble that psy chia trists are more likely to em ploy other treat ments (such as be hav iour ther apy), that they are more likely to see chil dren re sis tant to medi ca tions, or that other medi ca tions not ex am ined in this study are pre scribed by this group of prac ti tio ners. Gen eral prac ti tio ners in this study saw just over one- quarter of those chil dren with ADHD, and over one- half of these chil dren were pre scribed stimu lant medi ca - tion. The rela tively low per cent age of chil dren with ADHD see ing gen eral prac ti tio ners may re flect ei ther the re fer ral of chil dren sus pected of hav ing ADHD to pe dia tri cians or the lack of case iden ti fi ca tion by gen eral prac ti tio ners in Mani toba. The phy si cian spe cialty pat tern varies con sid era bly across dif fer ent re gions of the prov ince. Not sur pris ingly, given the con cen tra tion of pe dia tri cians and psy chia trists in Win ni peg and Bran don, chil dren living in ru ral ar eas of Mani toba are less likely to be di ag nosed by spe cial ists rather than gen eral prac ti tio ners than are chil dren living in ur ban ar eas. Win ni - peg chil dren with ADHD are the most likely to see psy chia - trists, and chil dren with ADHD in both Win ni peg and Bran don are more likely to see pe dia tri cians than are chil dren with ADHD in ru ral Mani toba. These pat terns may partly ex - plain the al most 4- fold varia tion in rates of ADHD and the over 8- fold variation in rates of stimu lant medi ca tion found across the larger re gions of the prov ince. Fewer chil dren from ru ral ar eas have ac cess to spe cial ists, with many ru ral ar eas served ex clu sively by general prac ti tio ners. Gen eral practi - tio ners may be less likely to rec og nize mental health prob - lems (34 36) and have less train ing rec og niz ing and treating

7 270 The Canadian Journal of Psychiatry Vol 46, No 3 ADHD, lead ing to less ap pro pri ate di ag no sis and treat ment of this dis or der. Thus, al though our re sults seem to sup port the find ing that ADHD is more strongly as so ci ated with ur ban liv ing (37,38), this as so cia tion is con founded by the avail abil - ity of spe cial ists in our study. What is per haps sur pris ing is that, even once di ag nosed, chil - dren liv ing in the north of the prov ince are less likely to re - ceive medi ca tions, re gard less of phy si cian spe cialty. The much lower rates of medi ca tion use for north ern resi dents may be at least par tially ex plained by the use of nurs ing sta - tions in north ern re gions. Data on drugs dis pensed to Mani - toba First Na tions peo ples by north ern nursing sta tions are miss ing from the phar ma ceu ti cal da ta base (19). This does not ex plain the lower rates of di ag no sis and medi ca tion use in the ru ral south, how ever. It is pos si ble that these dif fer ences may re flect dif fer ent prac tice styles of ur ban and ru ral phy si cians. Fur ther study of the dif fer ences be tween the di ag nos ing and pre scrib ing pat terns of ur ban and ru ral phy si cians would help clar ify this dis crep ancy. Our find ings re gard ing the re la tion be tween ADHD and in - come level dif fer from those gen er ally found in epi de mi ol - ogic stud ies, which tend to show that ADHD is more com mon in chil dren from lower SES groups (29) and that chil dren with lower SES are more likely to re ceive medi ca tion (9). We found, by con trast, that for chil dren living in ru ral ar eas both ADHD di ag no sis and medi ca tion use were more likely with higher, rather than lower, neigh bour hood in come lev els. Part of this find ing may be ex plained by the fact that those in iso - lated north ern ru ral ar eas tend to be clas si fied as low in come and are less likely to be cap tured in the phar ma ceu ti cal da ta - base due to the higher use of nurs ing sta tions, as dis cussed above. These re sults may also in di cate ac cess to services. Higher- income par ents living in ru ral ar eas may be more likely to have the edu ca tion needed to rec og nize the need for treat ment and the re sources nec es sary to seek it, es pe cially if this in volves trav el ling to an ur ban cen tre to see a spe cial ist. The medi ca tions ex am ined in this study are in sured bene fits in Manitoba; thus, their cost should not be a fac tor in differ - ences ob served in use across in come groups. What can the varia tions dis cussed above tell us about the pos - si bil ity of un der- or over di ag nos ing and treat ment of ADHD in Mani toba? We found that 1.5% of chil dren aged up to 19 years re ceived a di ag no sis of ADHD from a phy si cian during the course of this study. Con sid er ing that not all chil dren with ADHD will be di ag nosed or treated by a phy si cian, this proba bly un der es ti mates the true preva lence of the dis or der. In a sum mary of stud ies us ing large da ta sets and con sis tent di - ag no ses, Szat mari found the es ti mated preva lence of the dis - or der to range from 2.0% to 6.4% (29). We also found that less than 1% (0.89%) of Mani toba chil - dren re ceived stimu lant medi ca tion. Given the re quire ments for ac cu rate record- keeping for phar ma col ogi cal data, this rate is proba bly close to the true preva lence of medi ca tion use in the prov ince. This rate is also lower than the rate found in other ju ris dic tions. Us ing ad min is tra tive data on medi ca tion use, Rap pe ley and oth ers found that 1.1% of chil dren aged un - der 20 years were pre scribed MPH (15). Safer and Kra ger es - ti mated that 6% of school- aged chil dren were treated with MPH in Bal ti more County (9); when only school- aged (6- to 15- year- old) chil dren are in cluded in our re sults, we find that 1.5% are treated with stimu lant medi ca tion. Wol raich and oth ers found that 88% of physician- diagnosed chil dren were pre scribed MPH (3), whereas in our study, 58% of di ag nosed Mani toba chil dren were pre scribed stimu lant medi ca tion. Whether this in di cates that Mani toba phy si cians are more cau tious re gard ing the di ag no sis of ADHD and treat ment with stimu lant medi ca tion than are phy si cians in other juris - dic tions or whether this in di cates a lack of iden ti fi ca tion and treat ment of ADHD is an im por tant ques tion for fu ture re search. Limi ta tions Ad min is tra tive claims data pro vide a unique op por tu nity to study ADHD and stimu lant medi ca tion use at the population level, but they have limi ta tions. Rather than de scrib ing the preva lence of this dis or der, the data de scribe the preva lence only for those who are di ag nosed by a medi cal prac ti tio ner. There could be many chil dren with ADHD who have never been di ag nosed with the dis or der or who have been di ag nosed or treated by a non physi cian (for ex am ple, a psy cholo gist). These chil dren would not get cap tured in the current study. Like wise, there may be chil dren who have been di ag nosed, and even treated for ADHD by a medi cal prac ti tio ner, who do not ac tu ally have the dis or der. Fi nally, there may also be chil - dren di ag nosed with ADHD by a medi cal prac ti tio ner whose di ag no sis did not get en tered on the claims rec ord for some rea son. If these chil dren were not pre scribed medi ca tion (or did not fill their pre scrip tion), they would not have been cap - tured in the current study. An other limi ta tion of the cur rent study is that we have looked only at the 3 stimu lant medi ca tions most likely to be used to treat ADHD during the study year (30). The lit era ture sug - gests that a small pro por tion of chil dren with ADHD may be pre scribed other types of medi ca tions, such as tri cyc lic anti - de pres sants and an tipsy chot ics (13). Chil dren with a di ag no - sis of ADHD who were pre scribed these medi ca tions ex clu sively would be clas si fied in this study as chil dren not on medication. Conclusions The pat tern of re gional varia tion found in this study sug gests that both the di ag no sis and treatment of ADHD are influ - enced strongly by the prac tice styles of lo cal phy si cians. It is pos si ble that chil dren in ar eas with lower rates of di ag no sis and treat ment are not get ting serv ices they need. Given the ef - fi cacy of psy chostimu lant medi ca tion for re duc ing the symp - toms of ADHD (11,13 15,39 41), ap pro pri ate di ag no sis and treat ment have the po ten tial to im prove sig nifi cantly the lives of those af fected by this dis or der. Al ter nately, it is pos si ble

8 April 2001 ADHD in Manitoba Children 271 that those in ar eas with higher rates of di ag no sis and treat ment are getting un nec es sary serv ices. Miller and oth ers es ti mated that 10% to 40% of the cases in their study re ceived MPH in - ap pro pri ately (11). Either al ter na tive is un ac cept able, and fur ther re search is nec es sary to en sure Mani toba chil dren with ADHD are re ceiv ing ap pro pri ate care and treat ment. Acknowledgements This work was supported by an op er at ing grant to the senior author from the Manitoba Health Re search Council (# ). We ac knowl edge the St Boni face Hospital Re search Centre and are in - debted to the Health In for ma tion Serv ices, Mani toba Health, for pro vid ing data. We acknowledge Mr Pat rick Nicol and Dr Patricia Mar tens for analytic sup port, and Dr Patricia Fergusson, Dr Anita Kozyrskyj, Dr Col leen Metge, Dr Mi chael Mof fatt, and Dr Michael Teschuk for assistance with con cep tual is sues. Note This value underestimates the true contact rate, because contacts without proper identification num bers, including approximately 3000 unregistered new borns, were ex cluded from the calculation. References 1. Rich ters JE, Arnold E, Jensen PS, Abik off H, Con ners CK, Green hill LL, and oth - ers. NIMH col labo ra tive multisite mul ti mo dal treat ment study of chil dren with ADHD: I. Back ground and ra tion ale. J Am Acad Child Psy chia try 1995;34: Swan son JM, Ler ner M, Wil liams L [let ter]. More fre quent di ag no sis of at ten tion deficit- hyperactivity dis or der. New Engl J Med 1995;333: Wol raich ML, Lind gren S, Strom quist A, Milich R, Davis C, Wat son D. Stimu lant medi ca tion use by pri mary care phy si cians in the treat ment of at ten tion defi cit hy - per ac tiv ity dis or der. Pe di at rics 1990;86: Baum gaertel A, Wol raich ML, Di etrich M. Com pari son of di ag nos tic cri te ria for at - ten tion deficit dis or ders in a Ger man ele men tary school sam ple. J Am Acad Child Psy chia try 1995;34: Co hen D. Just say no to class room drugs. Globe and Mail 1999 Dec 6;A Ko lata G. Boom in ri ta lin sales raises ethi cal is sues. New York Times 1996 May 15;C8. 7. Han cock L. Mother s little helper. Newsweek 1996 March 18; Citi zens Com mis sion on Hu man Rights. Psy chia try: be tray ing and drugging chil - dren. Los Angeles (CA): Citi zens Com mis sion on Hu man Rights; Safer DJ, Krager JM. A sur vey of medi ca tion treat ment for hy per ac tive/in at ten tive stu dents. JAMA 1988;260: Safer DJ, Zito JM, Fine EM. In creased meth ylpheni date us age for at ten tion deficit dis or der in the 1990s. Pe di at rics 1996;98(6 Pt 1): Miller A, Lee SK, Raina P, Klassen A, Zu pan cic J, Olsen L. A re view of thera pies for attention- deficit/hy per ac tiv ity dis or der. 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Arch Gen Psy chia try 1999;56: The Mani toba Pre scrib ing Prac tices Pro gram, Win ni peg (MB): The Col lege of Phy si cian and Sur geons; Zito JM, Safer DJ, Rid dle MA, John son RE, Speedie SM, Fox M. Preva lence varia - tions in psy cho tropic treat ment of chil dren. J Child Ado lesc Psy cho phar ma col 1998;8: Rap pley MD, Gardiner JC, Jet ton JR, Houang RT. The use of meth ylpheni date in Michi gan. Arch Pe di atr Adolesc Med 1995;149: Metge C, Black C, Pe ter son S, Ko zyr skyj AL. The popu la tion s use of phar ma ceu - ti cals. Med Care 1999;37(6 Suppl):42S 59S. Clinical Implications It is likely that some Manitoba children with ADHD are not receiv - ing services they need; conversely, some Manitoba children may be receiving treatment for ADHD when it is unnecessary. Diagnosis and pharmacological treatment of ADHD in Manitoba are dependent on region of residence, socioeconomic resources, and physician specialty. 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9 272 The Canadian Journal of Psychiatry Vol 46, No 3 Résumé Le trouble d hyperactivité avec déficit de l attention chez les enfants du Mani toba : taux des diagnostics médicaux et des traitements aux psychostimulants Ob jec tif : Dé crire le taux des di ag nos tics de trou ble d hy per ac tiv ité avec déficit de l at ten tion (THADA) don nés par les médecins aux en fants de la prov ince du Mani toba ainsi que le taux d u tili sa tion de psy chostimu lants par ces en fants. Méth odes : Cette étude de scrip tive a passé en revue les dos si ers ad min is tratifs in for ma tiques des vis ites chez le méde cin et des or - don nances four nies, en vue d ex am iner une co horte trans ver sale re pré sen ta tive d en fants ayant reçu un di ag nos tic de THADA, ou à qui l on a pre scrit des stimu lants, ou les deux. Nous avons trouvé en fants ay ant reçu un di ag nos tic de THADA sur une pé ri - ode de 24 mois, ou une or don nance de stimu lants sur une pé ri ode de 12 mois, ou les deux. Les taux ont été cal culés selon l âge, le sexe, la ré gion de rési dence, le ni veau de revenu du quartier et la spé ci al ité du méde cin. Résul tats : Parmi les en fants du Mani toba, 1,52 % ont reçu un di ag nos tic médical de THADA et 0,89 % ont ob tenu des stimu lants. Selon la ré gion, les taux de di ag nos tic de THADA vari aient presque de 4 fois, et de plus de 8 fois pour les médica ments pre scrits. Les ré gions ur baines dé te naient des taux plus élevés que les zones ru rales, peu im porte la spé ci al ité du médecin. Les taux de diag - nos tics et d or don nances vari aient selon la spé ci al ité du médecin, et les taux les plus élevés se trou vaient chez les pédia tres. Un gra di ent de revenu était mani feste dans les ré gions ru rales, et les taux de di ag nos tics de THADA et de médica ments pre scrits aug - men taient au même rythme que le ni veau de revenu du quartier. Con clu sions : Le modèle de variation ré gion ale con staté dans cette étude in dique que le di ag nos tic et le traite ment du THADA au Mani toba subis sent for te ment l in flu ence des styles de pra tique des médecins lo caux.