Attention-deficit hyperactivity disorder with and without oppositional defiant disorder in 3- to 7- year-old children

Transcription

1 Attention-deficit hyperctivity disorder with nd without oppositionl defint disorder in 3- to 7- yer-old children Christin Kdesjö PhD; Bruno Hägglöf MD PhD, Deprtment of Child nd Adolescent Psychitry (CAP), University of Umeå, Umeå; Björn Kdesjö MD PhD, Deprtment of CAP, University of Göteborg, Göteborg; Christopher Gillberg* MD PhD, Deprtments of CAP, University of Göteborg, Sweden nd University of London, London, UK. *Correspondence to finl uthor t Deprtment of Child nd Adolescent Psychitry, Göteborg University, Kungsgtn 12, SE , Göteborg, Sweden. E-mil: christopher.gillberg@pedit.gu.se Attention-deficit hyperctivity disorder (ADHD) is common neurodevelopmentl disorder with high degree of ssocited behviourl problems. In order to study chrcteristics of ADHD with nd without oppositionl defint disorder (ODD) in representtive group of young children with clinicl impirment in Sweden, 131 children (101 mles, 30 femles) with ADHD (men ge 5 yers, SD 1 yer 5 months; rnge 3 to 7 yers) were cliniclly exmined, nd their prents interviewed. Independent questionnire dt (Child Behvior Checklist, ADHD Rting Scle-IV, ODD Rting Scle-IV, Conners Hyperctivity Index) were collected. For comprison 131 children without ADHD were mtched for sex, ge, mritl sttus, nd socioeconomic sttus (115 mles, 16 femles; men ge 4 yers 10 months, SD 1 yer 5 months; rnge 3 to 7 yers). Sixty percent of those with ADHD met full DSM-IV criteri for ODD. Only 10 of the 131 children with ADHD hd no symptoms of ODD t ll. The rte of children meeting full dignostic criteri for ODD ws similr cross ll ge cohorts. Mles were overrepresented in ODD, s were children of divorced prents nd of mothers with low socioeconomic sttus. ADHD combined subtype ws stble independent fctor influencing the dignosis of ODD, regrdless of psychosocil fctors. Those with ADHD with ODD consistently showed higher rtes of ADHD symptoms thn did those with ADHD without ODD. The prevlent comorbidity of ADHD with ODD indictes tht ll children presenting with ADHD or ODD symptoms need to be ssessed with view to exploring both types of problem behviours. The link between ODD nd some psychosocil vribles indictes the need to ddress these, possibly by mesures such s prent trining nd network support. There is growing wreness tht comorbidity in child nd dolescent psychitry plys n importnt role nd tht the presence of ssocited conditions in ny given disorder my lter the ssocited fetures, outcome, nd response to interventions in importnt wys (Cron nd Rutter 1991, Verhulst nd vn der Ende 1993). Attention-deficit hyperctivity disorder (ADHD) is one of the most common of ll neurodevelopmentl disorders, nd is, therefore, of gret clinicl importnce in child nd school helth services s well s in developmentl peditrics nd child psychitry. ADHD is usully ssocited with other lerning nd behviourl problems (Jensen et l. 1997), s shown in both in clinicl (Biedermn et l. 1991) nd popultion studies (Gillberg 1983, Kdesjö nd Gillberg 2001). One of the most common types of ssocited problems in ADHD is the constelltion of symptoms referred to s oppositionl defint disorder (ODD; Americn Psychitric Assocition 1994). The essentil fetures of ODD re recurrent pttern of negtivistic, defint, disobedient, nd hostile behviour towrd uthority figures, which leds to cliniclly significnt impirment in socil or cdemic functioning (Loeber et l. 2000). A relted group of problem behviours, lso often ssocited with ADHD is conduct disorder or conduct problems (Loeber nd Keenn 1994, Frone et l. 1998). Erly onset of conduct disorder problems is often preceded nd predicted by persistent ODD symptoms (Loeber et l. 2000). Disruptive behviours in very young children seem to be predictive of incresed generl psychitric morbidity of both internlizing nd externlizing symptoms (Cmpbell 1995, Lvigne et l. 1998). Symptoms of ODD re commonplce in the preschool yers nd it is only their mgnitude, inflexibility, or persistence t lter ge tht would justify their being considered sign of disorder or devince from normtive vlues (Rey 1993). In review of five community studies, Rey (1993) concluded tht the verge prevlence of ODD is 5.7% (rnge 1.7 to 9.9%). No firm conclusion cn be reched regrding the prevlence of ODD s function of ge (Loeber et l. 2000). Severl studies show very high degree of overlp with ADHD in children primrily dignosed s hving ODD (Spitzer et l. 1990), nd vice vers (Speltz et l. 1999). When preschool onset ODD is comorbid with ADHD, then the risk of follow-up disruptive nd conduct behviours nd developmentl disorders is greter thn when ODD occurs lone (Speltz et l. 1999). Studies on psychosocil correltes of ADHD nd ODD hve shown tht persistent ODD occurring together with ADHD is ssocited with negtive prenting prctices nd mternl psychitric disorders (August et l. 1999). The interction of child disruptive behviour nd prentl feedbck strtegies hs been discussed by Ptterson (1992) s predictor of future socil-djustment problems. Prent trining hs been shown to effectively reduce the risk of lter mjor conduct problems in ADHD with ODD (Pelhm et l. 1998). Therefore, it seems resonble to recognize these problems t n erly ge so tht pproprite interventions might be offered. Given the limited informtion vilble on preschool children with ADHD, we decided to study the prospective outcome of of 3- to 7-yer-old children with ADHD, with nd without erly onset ODD. Our ims in this bseline study Developmentl Medicine & Child Neurology 2003, 45:

2 were to: (1) determine the rte of ODD in Swedish 3- to 7- yer-old clinic ttenders with ADHD; (2) evlute the effect of ge, sex, ADHD subtype, nd mternl-socil fctors on ODD-dignosis; nd (3) study the symptomtology of ODD nd relted problems in group of 3- to 7-yer-old clinic ttenders with ADHD (with nd without ODD) nd in comprison group. Method Children (n=262), 3 to 7 yers of ge, were studied in detil in prospective nd controlled longitudinl survey of intervention effects in ADHD. The number of children t ech yer of ge were s follows: 3 yers, n=49; 4 yers, n=62; 5 yers, n=65; 6 yers, n=39; nd 7 yers, n=47. The study groups comprised 131 children (101 mles, 30 femles) with ADHD nd 131 children without ADHD (115 mles, 16 femles), who served s the comprison group. Men ge ws 5 yers (SD 1 yer 5 months) in the ADHD group nd 4 yers 10 months (SD 1 yer 5 months) in the comprison group (ns). The present report is concerned with dt collected before intervention. ADHD GROUP The criteri for inclusion in the ADHD group were: (1) prent/cregiver(s) concerned bout child s ttention/ctivity/ impulsivity problems nd wnted intervention; (2) residence in the county of Värmlnd, Sweden t the time of the study; (3) child s ge 3 to 7 yers; (4) full DSM-IV ADHD criteri (Americn Psychitric Assocition 1994) met ccording to neuropsychitric evlution (see Procedure); (5) durtion of problems 1 yer or more; nd (6) significnt impirment due to ADHD in everydy life in two settings ccording to prent(s) nd techer nd/or clinicl exmintion in connection with neuropsychitric ssessment (Kdesjö et l. 2001). According to the results of clinicl evlution, the following dditionl requirements were then pplied: (1) ADHD problems not ccounted for by lerning disbility*, utism, psychosis or serious fmily dysfunction; (2) bsence of mjor chronic disese, such s dibetes or cerebrl plsy; nd (3) prents fluent in Swedish. The totl number of eligible prticipnts with ADHD ws originlly 143 children who were ssigned for prticiption. Twelve of these (8%) dropped out, they did not differ significntly from those who prticipted in terms of number of ADHD symptom criteri met (10.8 versus 12.2, ns). Two specilized centres for the evlution nd tretment of children with neuropsychitric disorders hve been in existence in the county of Värmlnd for mny yers, nd the vst mjority of ll preschool children suspected of hving ADHD re referred to either of these. All children (nd their prents) referred to these centres over 42-month period who met inclusion nd exclusion criteri were invited to prticipte in the intervention progrmme nd reserch protocol. The only other centre providing dignostic services nd tretment for children with ADHD, the Child nd Adolescent Psychitric Clinic, hd registered 14 children ged 3 to 7 yers of ge with ADHD (not prt of the present study) during the corresponding 42-month period. No other children *US usge: mentl retrdtion. with ADHD hd been dignosed by services ctering for children in the county of Värmlnd during the relevnt time period. For tht reson the smple of 131 children who prticipted in the study is believed to be representtive of cliniclly impired children with ADHD in the community. COMPARISON GROUP A comprison group ws recruited through dy-cre centres in the county of Västerbotten, ttended by the mjority of ll 3 to 7 yer olds, by inviting prents with 3 to 7-yer-old child to prticipte in reserch project relting to child development. Two children were chosen for ech of the first 65 children included in the ADHD group plus one more (so s to equl the totl number of children in the ADHD group) nd were mtched for sex, ge (±2.4 months), prents mritl sttus, child s doption sttus, nd socioeconomic sttus (Sttistics Sweden 1999) with the children in the ADHD group. There were reltively more mles mong the first 65 children with ADHD leding to slight over-representtion of boys in the comprison group (115 of 131 versus 101 of 131, p<0.05). One exclusion criterion ws previous ADHD dignosis (two children were excluded for this reson). Nevertheless, 2% of the comprison group hd six or more hyperctivity impulsivity symptoms ccording to prentl scoring on the ADHD Rting Scle (DuPul 1998), indicting the possible presence of ADHD. Otherwise the sme exclusion criteri s in the ADHD group were used. More mothers in the ADHD group turned out to be mnul workers (98 versus 68 in the comprison group, p<0.001) nd unemployed (28 versus seven in the comprison, p<0.001). Mternl ge ws somewht lower in the ADHD group (men ge 32 yers 4 months versus 34 yers 2 months, p<0.01). There ws no difference cross groups in respect of prents mritl sttus, number of siblings, sibship rnk, pternl voction or unemployment, or pternl ge. The children were living in single-prent fmilies more often thn children in the generl Swedish popultion (in 29% nd 25% compred with 20%; Andersson 1996). This pplied in both the ADHD nd comprison groups s consequence of the mtch for mritl sttus. Ech comprison group fmily prticipting in the project received two movie tickets. Informed consent ws obtined from prents of ll the prticipting children. The study ws pproved by the Reserch Ethics Committee of the Medicl Fculty, Umeå University, Sweden. PROCEDURE All children in the group with ADHD received n in-depth neuropsychitric evlution. The evlution comprised: (1) prent interview in ccordnce with the technique nd formt of the Dignostic Interview for Children nd Adolescents (Reich 2000). The items of ADHD nd ODD in DSM-IV were covered in detil. Psychometric studies for this type of interview hve yielded resonble test retest relibility (Reich 2000). Given this we refrined from performing new relibility study in the context of the present reserch. (2) Child observtion nd exmintion. The child ws exmined in structured motor ssessment procedure nd the behviour observed during free ply lsting for bout hlf n hour (for more informtion see Kdesjö et l. 2001). (3) Severl questionnires were completed by prents giving prent questionnire dt in ADHD nd 694 Developmentl Medicine & Child Neurology 2003, 45:

3 comprison groups: () The Conners Hyperctivity Index: 10-item ttention-deficit hyperctivity-oppositionl/defint questionnire (Conners 1969) tht is well vlidted in mny countries. Scores rnge from 0 to 30, higher scores indicting more bnormlity. (b) The Child Behvior Checklist; Achenbch 1991) which is well-vlidted stndrdized ssessment protocol for child behviour problems. We did not use the competence scle. (c) The ADHD Rting Scle-IV contining 18 items referring to the dignostic criteri of the DSM-IV with very good psychometric properties (DuPul 1998). Ech item is rted for frequency of symptom occurrence on 4-point Likert scle, rnging from 0 (rrely) to 3 (very often). Scores of 2 or 3 on individul items were regrded s indicting presence of symptom. (d) An ODD Rting Scle-IV developed for the purpose of the present study nd contining eight items scored in the sme wy s the former scle referring to the dignostic criteri for ODD of the DSM-IV. In the ADHD group, ODD Rting Scle-IV protocols were missing for eight children. These eight children hd no significnt difference in the levels of ODD or ADHD symptoms ccording to prent interview compred to the remining 123 children. In ccordnce with previous uthors in the field (Lhey et l. 1998, Shelton et l. 1998), dignoses were bsed on the dt obtined t prent interview fter clinicl observtion nd exmintion of the child. Questionnire dt did not form prt of the bsis for dignostic decisions, nd were completed by the prents without knowledge of the dignosis mde. The men number of ADHD symptoms ccording to DSM-IV shown by ech child in the ADHD group ws 12.2 (SD 2.1). Symptom counts ccording to DSM-IV were eqully high regrdless of the child s ge nd there were few effects of ny bckground fctors studied on the level of ADHD symptomtology s judged by clinicl interview. More detils regrding the clinicl presenttion of ADHD symptoms, sociodemogrphic correltes, nd reltionship between prent nd clinicin s rtings hve been published in seprte report (Kdesjö et l. 2001). The ADHD group ws subdivided into inttentive subtype (n=25), hyperctive impulsive subtype (n=68), nd combined subtype (n=38). CHILD OBSERVATION AND EXAMINATION: COMPARISON GROUP On the bsis of informtion obtined t brief interview covering worries/concerns tht the prent might hve regrding child development, behviour, or emotionl problems the exclusion criteri were pplied in the comprison group. No forml systemtic ssessment ws mde of the children in the comprison group t the time of inclusion in the study. The sme questionnires (see Procedure items 3 d) tht were given in the ADHD group were lso completed. A follow-up study of both groups is under wy in which the sme ssessment bttery is pplied in both groups. STATISTICAL METHODS The following tests were used depending on the type of nlysis: χ 2 test with Ytes correction whenever pproprite, independent smples t-test, ANOVA with Bonferroni correction for chnce significnces, Person s correltion coefficients, nd logistic regression nlysis. When dt were not normlly distributed, 95% confidence intervls (Poisson) distribution, Kruskl Wllis nd Mnn Whitney U tests were used. Results PREVALENCE OF ODD IN CHILDREN WITH ADHD ACCORDING TO PARENT INTERVIEW DATA Sixty percent (79 children) of those with ADHD met full DSM-IV criteri for ODD, mening tht they hd shown four or more ODD symptoms tht hd cused clinicl impirment for long period of time (one yer or more). Of those with the combined subtype of ADHD 74% met dignostic criteri for ODD. The men number of ODD symptoms in the ADHD group ws 3.8 (CI 3.4 to 4.1): 4.7 (CI 4.1 to 5.3) in the combined subtype, 3.5 (CI 3.0 to 4.0) in the hyperctive impulsive subtype, nd 3.1 (CI 2.4 to 3.8) in the inttentive subtype (combined versus inttentive nd hyperctive impulsive p<0.005 nd p<0.01 respectively). Only 10 of the 131 children with ADHD hd no symptom of ODD t ll. BACKGROUND FACTORS IN CHILDREN WITH ADHD WITH AND WITHOUT ODD The two groups of ADHD (with nd without ODD) were compred on number of bckground fctors: ge, sex, ADHD subtype (child fctors); mternl ge, number of siblings, sibling rnk, socioeconomic sttus, mritl sttus, fmily type, mternl profession, income erner s employment (fmily fctors). Age The rte of children meeting full dignostic criteri for ODD ws similr cross ll five ge cohorts. Thus, the rte of ODD mong 3-yer-olds with ADHD (65%) ws lmost exctly the sme s the corresponding rte mong 7 yer olds (68%). Sex Girls were under-represented in the group of children with ADHD with ODD (p<0.05). ADHD subtype The inttentive subtype of ADHD ws under-represented mong children with ODD (p<0.05) when compred with other ADHD subtypes. SOCIODEMOGRAPHIC FACTORS Children meeting dignostic criteri for ADHD with ODD hd prents who were divorced more often thn children who did not meet such criteri (73 vs 27%, p<0.01). A lower sttus mternl profession ws lso significntly ssocited with ODD dignosis (67 vs 33%, p<0.01). There ws no significnt difference in respect of socil clss, type of fmily (biologicl/stepfmily), prentl unemployment, number of siblings, or sibling rnk, cross those with nd those without ODD. LOGISTIC REGRESSION ANALYSIS On the bsis of the results from the univrite nlysis of the bckground fctors presented bove, the following vribles were included in univrite nd multivrite logistic regression nlyses in n ttempt to ccount for the vrince of the outcome of ODD: ADHD subtype, ge, nd sex (child fctors); occuption, mritl sttus, nd ge (mternl-socil fctors; see Tble I). In the univrite logistic regression nlysis, only ADHD combined subtype ws significnt mong the child fctors. Attention-Deficit Hyperctivity nd Oppositionl Defint Disorders Christin Kdesjö et l. 695

4 Among the mternl-socil fctors ll three were significnt. The odds of hving child with ODD were incresed for mothers with low-sttus professions, mothers who were divorced, nd mothers younger thn 29 yers of ge. When ll the vribles were included in the sme multiple logistic regression model, ADHD subtype ws still significnt Tble I: Univrite nd multivrite logistic regression nlysis of ODD outcome of preschool children (3 7 yers) with ADHD Fctors Univrite Multivrite OR 95% CI OR 95% CI Child ADHD subtype Inttentive 1 Reference 1 Reference Hyperctive/impulsive Combined Sex Femle 1 Reference 1 Reference Mle Age 3 7 yers Mternl Profession Non-mnul/high sttus 1 Reference 1 Reference Mnul/low sttus Mritl sttus Not divorced 1 Reference 1 Reference Divorced or single Age (y) >29 1 Reference 1 Reference < ODD, oppositionl defint disorder. with n odds rtio similr to tht of the univrite nlysis. Among the mternl fctors, only profession remined significnt (lbeit with lower odds rtio). To explore further the stbility of ADHD subtype s n independent fctor we looked t its interction with ll three possible pir-wise combintions of the three mternl fctors. Using these interctions in the model did not chnge the odds rtios of ADHD subtype much. In the multivrite nlysis there were significnt ssocitions with the outcome for ODD dignosis in the two interction nlyses including mternl profession. Prticulrly notble ws the interction between mother s profession low nd mritl sttus seprted (odds rtio 5.85, ODD versus no ODD dignosis). SYMPTOMATOLOGY ACCORDING TO PARENT QUESTIONNAIRE DATA IN ADHD SUBGROUPS WITH AND WITHOUT ODD AND COMPARISON GROUP There were considerble differences cross ADHD nd comprison children in respect of ADHD-relted symptoms ccording to both the Conners nd the ADHD rting scles (Tble II). There were lso mrked differences s regrds ODD symptoms s mesured on the ODD Rting Scle nd the Aggressive nd Delinquent Behviour scles included in the externlizing fctor on the Child Behvior Checklist. In ddition the groups were seprted on the Anxious/Depressed scle (4 to 7 yers; see Tble II) included in the Internlizing scle of the Child Behvior Checklist s well s on the Internlizing Problems scle for the 3-yer-olds. INDIVIDUAL ODD SYMPTOMS ACCORDING TO PARENT INTERVIEW DATA IN CHILDREN WITH ADHD WITH AND WITHOUT A DIAGNOSIS OF ODD Even though there ws significnt difference cross the ADHD subgroups with nd without ODD with regrd to the occurrence of the ODD-symptom loses temper (p<0.001), lrge mjority (64%) of the subgroup of individuls with ADHD Tble II: Symptomtology ccording to prent questionnire dt in ADHD nd comprison cses Scle (rnge) ADHD ADHD Comprison p b +ODD ODD group 4 7 yers (n=63) (n=43) (n=104) 3 yers (n=16) (n=9) (n=26) Men (SD) Men (SD) Men (SD) (i) (ii) (iii) Conners Hyperctive Index (0 30) 19.7 (6.0) 14.3 (4.9) 3.6 (3.5) ADHD Rting Scle-IV (0 54) 34.3 (9.3) 28.4 (9.1) 7.6 (6.0) ODD Rting Scle-IV (0 24) 13.3 (5.0) 7.8 (4.0) 3.5 (2.7) Child Behvior Checklist (CBCL) CBCL 4 7 Anxious/depressed (0 28) 5.2 (4.8) 3.2 (3.6) 1.5 (2.6) e CBCL 4 7 Socil problems (0 16) 4.7 (3.2) 3.5 (2.6) 1.5 (2.6) b CBCL 4 7 Attention problems (0 22) 8.0 (2.9) 7.0 (2.9) 1.4 (1.7) b CBCL 4 7 Delinquent behviour (0 26) 3.5 (2.4) 2.0 (1.7) 0.9 (1.1) c CBCL 4 7 Aggressive behviour (0 40) 22.2 (7.3) 14.8 (6.8) 5.4 (5.1) CBCL 4 7 Externl (0 66) 25.7 (9.0) 16.9 (7.6) 6.3 (5.8) CBCL 4 7 Internl (0 62) 8.3 (6.4) 6.5 (5.0) 3.1 (4.1) CBCL 4 7 Totl score (0 236) 56.4 (21.0) 41.2 (17.3) 15.3 (13.3) CBCL 3 Externl (0 52) 29.4 (9.9) 19.1 (9.8) 6.5 (5.3) c CBCL 3 Internl (0 50) 15.3 (8.0) 7.3 (5.2) 3.9 (4.0) d p< (i) versus (ii) versus (iii); b p<0.001 (i)/(ii) versus (iii); c p< (i)/(ii) versus (iii), p<0.01 (i) versus (ii); d p< (i)/(iii), p<0.05 (i) versus (ii); e p< (i)/(ii) versus (iii), p<0.05 (i) versus (ii). 696 Developmentl Medicine & Child Neurology 2003, 45:

5 without ODD lso showed this symptom ccording to the prent interview dt (Tble III). One-third of the ADHD without ODD subgroup ws lso endorsed s being defies/refuses to comply. Argues with dults nd touchy/esily nnoyed occurred in slightly under one qurter, but other symptoms were t very low rte in the ADHD without ODD subgroup. Blmes others did not occur t ll in the ADHD without ODD subgroup (nd in 44% of those with ADHD with ODD, p<0.001). Spiteful/vindictive ws rre in both groups. Discussion These 3- to 7-yer-old clinic ttenders with ADHD hd very high risk of lso hving ODD. A recent popultion-study (Kdesjö nd Gillberg 2001) of 7-yer-old children showed lmost exctly the sme rte (60%) of ODD in ADHD. Other studies report n overlp of bout 30 to 60% between ADHD nd ODD, either lone or combined with conduct disorder, in both clinicl nd community surveys of children nd dolescents (Biedermn et l. 1991, Bumgertel et l. 1995, Wolrich et l. 1996, Eirldi et l. 1997). ODD ws significntly less common in children with ADHD of the inttentive subtype nd prticulrly frequent in the combined subtype. This finding ccords roughly with tht of recent US twin study in which ODD/conduct disorder ws ssocited with hyperctivity impulsivity in ADHD (Willcutt et l. 1999). ODD did not correlte with child s ge. This finding filed to support the hypothesis tht ADHD emerges first in developmentl trjectory (Biedermn et l. 1996), but rther tht ADHD nd ODD pper concomitntly. Possible explntions for this observtion re tht children with ADHD comorbid with ODD re those with impirment severe enough to wrrnt clinic referrl, or tht ADHD nd ODD reflect the sme underlying disorder rther thn being two seprte ctegories. There is some evidence tht sex differences in disruptive behviour do not emerge until fter 6 yers (Loeber et l. 2000). Our study suggested tht such differences re present from much younger ge, nd tht mles with the combintion of ADHD nd ODD re overrepresented in ll gegroups. Evidence regrding sex differences for ODD is quite inconsistent nd further studies re needed to determine whether there re sex differences in ODD with nd without comorbid ADHD (Lhey et l. 1999). In our study, inttentive, hyperctive impulsive, nd combined ADHD subtypes occurred in bout 20%, 50%, nd 30% of children respectively. This is different from most clinicl studies tht tend to find much higher rte of the combined subtype. However, much lower rtes (11 to 12%) hve been found in popultion studies in Europe (Bumgertel 1995, Kdesjö nd Gillberg 1998). When the vrious child nd fmily bckgrounds were nlyzed in multiple logistic regression nlysis, ADHD subtype (combined) ws strongly ssocited with dignosis of ODD. The min effect of this fctor ws not diminished by llowing for the contribution of psychosocil fctors in the nlysis. Of these, only mternl profession hd seprte effect. ADHD, with nd without ODD, ws seprted from the comprison group by very wide mrgin in respect of ll symptoms. This in itself provides some support for the vlidity of the ADHD construct. There were very lrge differences between ADHD nd comprison cses both in respect of ADHD- nd ODD-relted vribles. While the rte of externlizing symptoms ADHD ssocited behviours in prticulr ws incresed mnifold in the group with ADHD (especilly in the ADHD with ODD group), internlizing symptoms were t bout double the frequency (with little seprtion cross the ADHD+ODD nd ADHD ODD groups, t lest in the 4- to 7- yer olds). Some uthors hve proposed tht ODD my be n importnt mrker for lter internlizing symptoms such s depression (Cmpbell 1995). Longitudinl follow-up will revel to wht extent such link is present in this mteril lso. There were considerble differences cross those with ADHD with nd without ODD. Those with the combintion of ADHD nd ODD hd more of both hyperctivity nd inttention problems thn those with ADHD who did not meet the criteri for ODD. Very few (10 of 131) individuls with ADHD hd no symptoms of ODD. The mjority hd mny symptoms nd were reported to be ffected quite often or very often. Prticipnts in the comprison group very rrely hd such symptoms endorsed eqully often. Almost ll children with ADHD nd ODD were reported t prentl interview to often lose their temper. Even in the ADHD without ODD dignosis group this symptom occurred often in two-thirds of ll cses. Judging from prent questionnire dt this symptom ws very much less frequent in the comprison group. Nevertheless, it ws reported to occur occsionlly in more thn hlf of tht group. Thus, even though the symptom often loses temper ppers to be possible cndidte for n ODD-symptom possibly more intrinsic to the ADHD syndrome, conclusions hve to be tempered by the fct tht mild expressions of loss of temper is very common in the generl popultion of children lso. In order to ddress the issue of whether or not some symptoms of ODD my ctully be intrinsic to the syndrome of ADHD, one would need children with ADHD with nd without cliniclly dignosed ODD nd comprison children with nd without dignosed ODD. In the ongoing follow-up study of the 262 children included in the present study, intensive clinicl work-up is identicl in the two groups, but this ws not the cse in the exmintion when the children were of preschool ge. Our dt from the present report therefore cn only serve s bsis for suggesting tenttive questions on this hypothesis. Tble III: Symptoms of oppositionl defint disorder (ODD) ccording to DSM-IV interview in children with ttentiondeficit hyperctivity disorder (ADHD) with nd without comorbid dignosis of ODD Interview symptom ADHD with ODD ADHD without ODD of ODD n=79 n=52 % with symptoms % with symptoms Loses temper Argues with dults Defies/refuses to comply Annoys others Blmes others 44 0 Touchy/esily nnoyed Angry/resentful 71 7 Spiteful/vindictive 14 2 All differences, except spiteful/vindictive significnt t p< Attention-Deficit Hyperctivity nd Oppositionl Defint Disorders Christin Kdesjö et l. 697

6 LIMITATIONS This study, lthough likely to be representtive of Swedish preschool children with ADHD whose prents seek professionl help for them, is not popultion-bsed, limiting generlizbility s regrds ll young children with ADHD. Psychitric dignosis in smll children is questioned by its vlidity nd relibility. Though, in this study we used both ctegoricl (DSM-IV) nd dimensionl (Child Behvior Checklist) systems, nd lso different informnts (prents nd professionls) to evlute dignoses nd symptoms. Interviews nd clinicl exmintions were performed without blinding of the exminers to the group sttus of the child. Thus, findings my hve been bised by prior knowledge of wht cn be expected to be typicl symptoms of clinicl cse. Idelly children with nd without ADHD should be exmined without knowledge of group sttus. Nevertheless, we believe tht the very mrked discrepncy between the ADHD nd comprison groups in respect of ADHD symptomtology could not hve been cused by selection fctors only. Another limittion ws the fct tht comprison cses were not cliniclly investigted in exctly the sme mnner s the ptient group. Long-term follow-up of the children in this study will mke it possible to evlute the impct of symptoms, stbility over time, nd whether or not the severity of ADHD (with nd without ODD) or the vrious bckground fctors studied cn help in predicting outcome. CONCLUSIONS Developmentl peditricins, child psychitrists, nd child neurologists, s well s child nd school helth officers of vrious professions see very lrge number of young children with ADHD. They need to be very well informed bout the condition nd its most frequent ssocited fetures. The clinicl burden fcing fmilies of preschool children with ADHD is likely to be severe given the very high child symptom level both s regrds ttention deficits nd hyperctivity nd oppositionl defint behviours. 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