Attention-Deficit/Hyperactivity Symptoms in Icelandic Schoolchildren: Assessment with the Attention Deficit/Hyperactivity Rating Scale-IV

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1 Scandinavian Journal of Psychology, 1999, 40, Attention-Deficit/Hyperactivity Symptoms in Icelandic Schoolchildren: Assessment with the Attention Deficit/Hyperactivity Rating Scale-IV PÁLL MAGNÚSSON 1, JAKOB SMÁRI 2, *, HRO NN GRÉTARSDÓTTIR 2 and HRUND ÞRÁNDARDÓTTIR 2 1 Department of Child and Adolescent Psychiatry, National Uni ersity Hospital, Reykja ík, Iceland 2 Faculty of Social Science, Uni ersity of Iceland, Reykja ík, Iceland Magnússon, P., Smári, J., Grétarsdottir, H. and Þrándardóttir, H. (1999). Attention-Deficit/Hyperactivity Symptoms in Icelandic Schoolchildren. Scandina ian Journal of Psychology, 40, Four hundred and twenty-seven normal Icelandic children, six and eight years of age, were rated by their parents and three hundred and sixteen children by their teachers with the Teacher and Parent versions of the Attention Deficit/Hyperactivity Disorder Rating Scale-IV (AD/HDRS-IV). For two hundred and sixty-five of the children both parent and teacher ratings were obtained. The factor structures of the AD/HDRS-IV for parents and teachers were in line with theoretical expectations. A Hyperactivity-Impulsivity factor and an Inattention factor were thus well supported. The subscale reliabilities were high. Boys scored higher than girls on all measures and there was a decrease of symptoms with age for boys, as expected. There was evidence of convergent validity for all scales, but discriminant validity of the AD/HDRS-IV subscales is less certain. Generally the instruments seem promising for further research. Some differences are noted in comparison with earlier studies. Thus scores obtained in this study were somewhat lower than those found in American studies, especially for teachers. Also the prevalence of ADHD based on rating scales was lower than in comparable previous studies. The similarity in symptom structure between this and previous studies is emphasized, but the possible role of cultural homogeneity in explaining different results with regard to teachers ratings of symptoms is suggested. Key words: Attention Deficit/Hyperactivity Rating Scale-IV, Parent and Teacher ratings. Páll Magnússon, Department of Child and Adolescent Psychiatry, National Uni ersity Hospital, Dalbraut 12, 105 Reykja ík, Iceland. pama@rsp.is Attention Deficit/Hyperactivity Disorder (AD/HD) is a behavioural disorder of biological etiology. It is the most common of the disruptive behaviour disorders of childhood, the prevalence having been estimated at 4% in a study based on diagnostic interviews with parents and children (Shaffer et al., 1995). Prevalence rates of AD/HD as estimated by teacher completed symptom rating scales have ranged from 8.1% 17.8% (Baumgaertel et al., 1995; Gaub & Carlson, 1997; Wolraich et al., 1996). Prevalence rates have been found to vary as a function of age and gender. AD/HD cases constitute a large part of the referrals to child psychiatric clinics and reliable and valid instruments to screen and assess symptoms are of obvious importance. Behaviour checklists and rating scales have been widely used in the assessment of disruptive behaviour disorders in children. They are often completed by both parents and teachers, thus providing information on variability of behaviour across settings. This is particularly important in the case of AD/HD because of the DSM-IV (APA, 1994) requirement of impairment in two or more settings. The AD/HD Rating Scale-IV (Barkley, 1996b) is a recently developed instrument based on the DSM-IV diagnostic criteria for AD/HD. Recent research on the AD/HD Rating Scale-IV (AD/HDRS-IV) with large samples indicates that the psychometric properties are very good (Du- * Jakob Smári, Faculty of Social Science, University of Iceland, Reykjavík, Iceland, jakobsm@rhi.hi.is. Paul et al., 1997; 1998). A similar scale, the AD/HD Rating Scale (DuPaul, 1991), derived from DSM-III-R criteria (APA, 1987) has been shown to have adequate criterion-related validity and good reliability and to be sensitive to the effects of stimulant medication (Barkley et al., 1991). An Icelandic version of this scale has been shown to have good interrater reliability (a correlation of 0.86 between ratings of two different teachers) and internal consistency when filled out by teachers for a sample of six years old children (Vignisson, 1995). Factor analyses in recent research have consistently supported a two factor model of AD/HD (Baumeister et al., 1992; 1995; DuPaul et al., 1998; 1997; Healy et al., 1993; Lahey & Carlson, 1991), the symptoms of hyperactivity-impulsivity constituting one factor and the symptoms of inattention constituting another factor. This two factor model has become the basis of the subtyping of AD/HD in the DSM-IV (APA, 1994) where criteria are accordingly grouped in two clusters, Inattention and Hyperactivity-Impulsivity. According to Barkley (1996a), recent research may be leading to the conclusion that there exists a separate, distinct disorder of attention. There is some evidence indicating that the two sets of symptoms have a distinct developmental course. The symptoms of hyperactivity-impulsivity seem to appear typically at age 3 4 while the symptoms of inattention arise later, at 5 to 7 years of age (Barkley, 1996a). There is research to suggest that the levels of hyperactivity-impulsivity may Published by Blackwell Publishers, 108 Cowley Road, Oxford OX4 1JF, UK and 350 Main Street, Malden, MA 02148, USA. ISSN

2 302 P. Magnússon et al. Scand J Psychol 40 (1999) decline during the elementary-school years while the level of inattention may remain more stable (Barkley, 1996a; Hart et al., 1995). Gender differences in the prevalence of AD/HD are well documented. Reported male-female ratios vary from about 3:1 in population based samples to 6 : 1 and up to 9 : 1 in clinic-referred samples (Barkley, 1996a; Cantwell, 1996). Rating scales have consistently shown higher mean ratings of symptoms of inattention and hyperactivity for boys than for girls and this seems consistent across cultures (Arnold, 1996). In the present study the usefulness of the Icelandic version of the AD/HDRS-IV is investigated. One rationale for this is that it is very important to study cultural variance/invariance with regard to problems such as AD/HD. Variance/invariance may concern both the level of problems and factorial structure of problem domains (Crijnin et al., 1997; Reid, 1995). Studies of for example AD/HD in multiple cultures will hopefully help to disentangle cultural influences on both the presence of problems and the evaluation of problems (Reid, 1995). Weisz and Eastman s (1995) caution should, however, be heeded that cross-cultural psychopathology is still at a descriptive stage and that all explanations of observed differences are highly speculative. The objective of the present study is firstly to examine the psychometric properties of the Icelandic translations of the Parent and Teacher versions of the AD/HD Rating Scale- IV. Secondly the factor structure of the AD/HD Rating Scale-IV will be explored for both teachers and parents. Also the effects of age and gender will be examined. Then the relationship between the Parent and Teacher versions of the AD/HDRS-IV will be addressed. Finally the prevalence of AD/HD based on rating scales will be assessed. Where possible comparisons will be made with studies conducted in other cultures. Method Subjects Parents of 317 six year old children and of 259 eight year old children were asked to rate their children on the AD/HDRS-IV. Teachers of 197 six year old children and of 156 eight year old children were also asked to rate the children on the AD/HDRS-IV. Complete AD/HDRS-IV parent ratings were obtained for 235 six year olds (74%) and 192 eight year olds (74%). Teacher ratings were obtained for 186 six year olds (94%) and 130 eight year olds (83%). In all 479 children were rated of which 225 (47%) were boys and 254 (53%) were girls. For 265 of the children both parent and teacher ratings were available. Measures AD/HD Rating Scale-IV (Barkley, 1996b). There are two identical versions of this scale. One is intended for parents and the other for teachers. Eighteen symptoms derived from the DSM-IV are listed on the scale. Each of the 18 symptom items is rated on a 4 point Likert scale according to the frequency of its appearance in the child s behaviour as follows: never or rarely, sometimes, often and very often (0, 1, 2, 3). Three scores are calculated: a Total Score for all 18 items, an Inattention (IA) subscore summing the points scored on the 9 items categorized as Inattention symptoms in the DSM-IV (e.g. fails to give close attention to details or makes careless mistakes in schoolwork ) and a Hyperactivity-Impulsivity (HI) subscore for the items derived from the DSM-IV Hyperactivity and Impulsivity categories (e.g. runs about or climbs excessively in situations in which it is inappropriate ). The Icelandic version of the scale was translated jointly by an Icelandic child psychologist and an Icelandic developmental pediatrician and subsequently backtranslated in order to ascertain translation accuracy. In the present study the coefficients alpha of reliability were the following for the parent scales: 0.93 for the total scale, 0.87 for the Inattention scale and 0.89 for the Hyperactivity-Impulsivity scale. The corresponding reliabilities for the teacher scales were 0.95, 0.93 and Procedure Five elementary schools in the capital of Iceland were chosen for the study. It was attempted to recruit schools from all the major parts of the capital. Random samples of first and third grade classes of the five schools participated in the study. Teachers were asked to rate the children in their class on the Teacher version of the AD/HDRS-IV and send the children home with the Parent version of the AD/HDRS-IV as well as an envelope addressed to one of the authors. The material was coded so that the measures obtained from the teachers and the parents could be matched for each individual child. In two of the schools the teachers refused to participate as well as in one class of the third school. It should be emphasized that even teachers in the schools that refused participation were willing to send the children home with the lists to their parents. In all 265 children were rated by both their parents and teachers. The distribution of these children across age and sex categories is presented in Table 1. Of the two schools that refused participation one was an innercity school and the other suburban and of the three schools that participated two were inner city schools and the third suburban. Thus these schools do not seem to be systematically different. Also residence in Reykjavík is not as systematically related to SES as in many large cities in Europe and the US. However, in order to investigate a possible systematic bias due to dropout in the teacher sample, an analysis of variance was conducted on the parents total AD/HDRS-IV scores with presence-absence of teacher ratings, age and sex as independent variables. The analysis was non-significant for presence-absence of teacher ratings, F(1,419)=0.43, p There is thus no evidence that the sample rated by teachers only was skewed with regard to AD/HD symptoms. Of course this does not preclude that the sample of teachers may have been skewed. There is, however, no special reason to think that this was the case. Statistical analyses The effects of sex and gender on AD/HDRS-IV total scale scores for both the Parent and the Teacher versions, Hyperactivity and Inattention subscale scores were examined with two way analyses of variance. Principal components analyses were performed on the AD/HDRS-IV scores of the Parent and Teacher versions separately. Table 1. Distribution of Children Rated by Both Parents and Teachers across Gender and Age Categories Age 6yrs 57 8yrs 81 Boys 54 73

3 Scand J Psychol 40 (1999) Table 2. Means and Standard De iations of the Attention Deficit/ Hyperacti ity Rating Scales-IV (AD/HDRS-IV) Variable Boys 6 years 8 years 6 years 8 years M (SD) M (SD) M (SD) M (SD) Parents AD/HDRS 11.6 (10.2) 9.7 (9.8) 7.0 (5.8) 6.2 (6.4) IA 5.4 (4.7) 5.3 (5.2) 3.1 (2.9) 3.1 (3.5) HI 6.2 (6.0) 4.4 (5.1) 3.9 (3.6) 3.1 (3.3) Teachers AD/HDRS 12.6 (11.9) 7.5 (7.0) 4.1 (6.7) 3.0 (3.6) IA 6.6 (6.8) 4.2 (3.9) 2.1 (3.1) 2.1 (3.3) HI 6.0 (6.4) 3.2 (3.9) 2.0 (4.0) 0.9 (1.2) Note: IA is Inattention. HI is Hyperactivity-Impulsivity Factor extractions were based on the scree test and factors submitted to an oblique rotation. Correlations were calculated between scores on the Teacher and the Parent versions of the AD/HDRS- IV. Also correlations were calculated between similar and different subscales of the AD/HDRS-IV within and across raters. Finally the prevalence of AD/HD was assessed based on the AD/HDRS- IV rating scales referring to DSM-IV criteria. Results Means and standard deviations were calculated for all total scale and subscale scores for each subgroup (see Table 2). Analyses of variance were performed with age and sex as the independent variables and total scores on AD/HDRS- IV for parents, AD/HDRS-IV total scores for teachers, and each of the AD/HDRS-IV subscale scores as dependent variables. There were main effects of sex in parents ratings for total scores (F(1,423)=25.91, p 0.001), for Inattention (F(1,423)=32.70, p 0.001) and for Hyperactivity-Impulsivity (F(1,423)=15.71, p 0.001). On all measures boys were rated higher than girls. There were no main effects for age in the parents ratings for total scores or for Inattention. On the other hand there was a significant effect of age for Hyperactivity-Impulsivity (F(1, 423)=8, 52, p 0.01). No interaction effect between age and sex was obtained. There were main effects of sex in teachers ratings for total AD/HDRS-IV scores (F(1, 312)=48.41, p 0.001), for Inattention (F(1, 312)=39.34, p 0.001) and for Hyperactivity-Impulsivity (F(1, 312)=39.16, p 0.001). In all cases boys were rated with more serious symptoms than girls. There were also main effects for age in teachers ratings for total AD/HDRS-IV scores (F(1, 312) =11.27, p 0.001), for Inattention (F(1, 312)=4.92, p 0.05) and for Hyperactivity-Impulsivity (F(1, 312)=14.88, p 0.001). These main effects were, however, moderated by interaction effects between sex and age for both total scores (F(1, 312)=4.55, p 0.05), and for inattention (F(1, 312= Attention Deficit/Hyperacti ity Rating Scale , p 0.05). This interaction indicated a decrease in dysfunction with age for boys but less so for girls. Principal components analyses were conducted on the AD/HDRS-IV scores for parents and teachers separately. Scree tests as well as Kaiser s criterion of eigenvalue 1 clearly indicated two factors in both cases and two factors were extracted. The first three eigenvalues in the solution for parents were 8.35 (46%), 1.25 (7.1%) and 0.95 (5.3%) and for teachers 9.81 (54%), 2.19 (12.2%) and 0.85 (4.7%). The factors were submitted to an oblique rotation (oblimin) as they might be expected to be highly correlated. The correlation turned out to be 0.59 for parents and 0.55 for teachers. The factor pattern matrices are presented in Tables 3 and 4. The pattern of loadings is in both cases close to what was expected. There is a clear Hyperactivity-Impulsivity factor and a clear Inattention factor. Only the item 15 showed a higher correlation with the wrong factor. Table 3. Attention Deficit/Hyperacti ity Rating Scale-IV (AD/ HDRS-IV).The Parent Version. Factor Pattern Matrix of an Oblimin Rotation. Only Factor Loadings 0.30 are shown. HI= Items expected to load on the Hyperacti ity-impulsi ity Factor. IA=Items expected to load on the Inattention Factor Item Factor 1 Factor 2 Communality HI 2. Fidgets with hands 4. Leaves seat Runs about Has difficulty playing 10. Is on the go Talks exces sively 14. Blurts out an swers 16. Difficulty wait ing turn 18. Interrupts or intrudes IA 1. Fails to give attention 3. Difficult to sustain attention 5. Does not seem to listen 7. Does not fol low through 9. Difficulty orga nizing 11. Avoids mental effort 13. Loses things Is easily dis tracted 17. Forgetful

4 304 P. Magnússon et al. Scand J Psychol 40 (1999) Table 4. Attention Deficit/Hyperacti ity Rating Scale-IV (AD/ HDRS-IV). The Teacher Version. Factor Pattern Matrix of an Oblimin Rotation. Only Factor Loadings 0.30 are shown. HI= Items expected to load on the Hyperacti ity-impulsi ity Factor. IA=Items expected to load on the Inattention Factor Item No. Factor 1 Factor 2 Communality HI 2. Fidgets with hands 4. Leaves seat Runs about Has difficulty playing 10. Is on the go Talks exces sively 14. Blurts out an swers 16. Difficulty wait ing turn 18. Interrupts or intrudes IA 1. Fails to give attention 3. Difficult to sustain attention 5. Does not seem to listen 7. Does not fol low through 9. Difficulty orga nizing 11. Avoids mental effort 13. Loses things Is easily dis tracted 17. Forgetful A Pearson correlation was calculated between total scores on the Parent and the Teacher scales. The correlation was r(265)=0.45, p In order to investigate discriminant and convergent validity of the AD/HDRS-IV subscales, correlations were calculated between the scales within the teacher and parent groups and between same and different scales across groups of raters (see Table 5). The correlations between different scales within groups of raters are substantially higher than the other correlations. The correlations between the ratings of parents and teachers for similar scales are moderate, but not substantially higher than correlations between different subscales across raters. This pattern of correlations indicates convergent but limited discriminant validity. Finally, the rate of AD/HD in Icelandic schoolchildren was assessed on the basis of parents and teachers ratings, Table 5. Correlations between AD/HDRS-IV Parent and Teacher Ratings on the Inattention and the Hyperacti ity-impulsi ity Subscales. All correlations significant at p (two-tailed) ) AD/HD Parent IA ) AD/HD Parent HI ) AD/HD Teacher IA ) AD/HD Teacher HI separately. It should be noted that because the sample is very small and because only rating scales were used the results can only be seen as very tentative estimates of prevalence. The DSM-IV criteria were applied concerning the number of symptoms required but not the requirement of impairment across settings. Accordingly it was considered that a child fulfilled the DSM-IV criteria for the Inattentive subtype if it obtained the score 2 or 3 on at least six items of the Inattention subscale. Similarly the score 2 or 3 on six items of the Hyperactivity-Impulsivity subscale was the criterion for the Hyperactive-Impulsive subtype and the score of 2 or 3 on six items of both subscales was the criterion for the Combined subtype. The results are shown in Table 6. Discussion The AD/HD Rating Scale-IV for both parents and teachers showed good psychometric properties. The factor structures were in line with theoretical expectations and the subscales reliabilities were very good. These results thus support the notion of Inattention and Hyperactivity-Impulsivity as two distinct dimensions on which children can be reliably rated by their parents and teachers. The moderate correlation between the AD/HDRS-IV total scores on the Parent and the Teacher versions substantiates the convergent validity of the total scales. The size of the correlation between the parents and teachers total scale ratings is similar to that found in previous studies on the preceding AD/HD instrument based on the DSM-III-R (DuPaul, 1991) and to what was found in a recent study on the AD/HDRS-IV (DuPaul et al., 1998). Table 6. Percentages of Children Satisfying the Criteria for the Inattenti e (IA), Hyperacti ity (HI) and Combined (C) Subtypes IA HI C TOTAL TEACHERS Boys PARENTS Boys

5 Scand J Psychol 40 (1999) The correlations between different AD/HDRS-IV subscales within groups of raters were, however, substantially higher than correlations between the same subscales across groups of raters. Only for Hyperactivity-Impulsivity is the correlation between the same subscales across raters higher than the correlation between different subscales across raters. Apparently this throws some doubt on the discriminant validity of the subscales. The lower correlation between raters for Inattention than for Hyperactivity- Impulsivity can perhaps be explained by the fact that signs of Inattention are probably less salient than signs of Hyperactivity-Impulsivity. Probably, however, the relatively low interrater correlations between the same subscales stem at least partly from the fact that the two groups of raters are not rating the children in the same context. With the exception of six years old boys the ratings on the AD/HDRS-IV by teachers are lower than those of parents. This is somewhat different from what has been found in studies using the same instrument in another culture (DuPaul et al., 1997; 1998) and in studies using a different instrument (Kadesjö & Gillberg, 1998). The school situation is probably more demanding with regard to attention than the home environment. The former environment might thus be expected to be more revealing of inattention than the latter. Teachers ratings of inattention are, however, overall lower than the parents ratings (with the exception of the youngest boys). This perhaps means that at least ordinary children or children with only marginal AD/HD symptoms are able to adapt to the more demanding but at the same time more structured situation at school, at least as well as the home environment. Another explanation for the somewhat lower teacher than parent ratings in this study may be that teachers are more lenient in their ratings as they see more children at the same age. This, however, does not explain the large difference between the mean scores found for teacher ratings in the present study and those found in DuPaul et al. (1997) with the same instrument. Whereas the Icelandic teachers generally rate the children somewhat lower than the parents on AD/HD symptoms, the US teachers rate them much higher than the parents do. It should, however, be noted that in a study by DuPaul (1991) using a rating scale based on the DSM-III-R teachers tended if anything to make lower AD/HD ratings than parents. A possible explanation for this is that in the DuPaul (1991) study a relatively homogenous sample of children was studied whereas in the later studies more heterogenous samples reflecting the US population as a whole were studied. Thus in the latter studies ethnic and cultural mismatches between raters and children are much more likely and such factors may lead to higher teacher ratings (Reid, 1995). Icelandic society is on the other hand highly homogenous and this may explain relatively low teacher ratings of AD/HD. Attempts were made to assess the prevalence of AD/HD. It should of course be emphasized that prevalence estimates Attention Deficit/Hyperacti ity Rating Scale 305 based on the present data are highly tentative both because of the limited size of the sample and because it is hazardous to assess prevalence based on rating scales alone. The total rate of AD/HD symptoms exceeding cut-off points are considerably lower than found in comparable teacher-based studies of German and American children (Baumgaertel et al., 1995; Gaub & Carlson, 1997; Wolraich et al., 1996). This is consistent with the lower scores overall for Icelandic children as rated by teachers. The reasons for this discrepancy are again not clear. Interestingly, lower means for teacher ratings were also found in a prior Icelandic study (Vignisson, 1995) of the DSM-III-R based AD/HD Rating Scale (DuPaul, 1991). Similarly in another Icelandic study (Hannesdóttir & Einarsdóttir, 1995) mean scores of total problem behaviour were found to be lower than American norms, especially for girls. It may again be speculated that cultural differences are responsible for this (Reid et al., 1998) or differences in the average pupil-teacher cultural match. These results indicate, however, the importance of cross-cultural studies of AD/HD symptoms. It seems particularly important in that context to distinguish possible cross-cultural differences in behaviour from differences in rater perception of behaviour. In conclusion, cross-cultural generalizability has many faces. It is important to distinguish between normative and structural aspects in this context. With regard to the structural aspects there is a correspondance between the ratings in our study and those of DuPaul (DuPaul et al., 1997; 1998), for example. This means that the factor patterns are highly similar across cultures and also the correlations between different raters. On the other hand the normative values are quite different, at least for teachers. We have pointed out several possible reasons for this discrepancy but in fact they are impossible to disentangle on the basis of the present data and thus await further empirical research. Páll Magnússon Department of Child and Adolescent Psychiatry, National University Hospital, Reykjavík, Iceland: Jakob Smári, Hrönn Grétarsdóttir and Hrund Þrándardóttir, Faculty of Social Science, University of Iceland, Reykjavík, Iceland. The authors wish to thank Dr. Russell A. Barkley for valuable comments on an earlier version of the manuscript. REFERENCES American Psychiatric Association (1987). Diagnostic and statistical manual of mental disorders (3rd ed. rev.). Washington, DC: Author. American Psychiatric Association (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author. Arnold, L. E. (1996). Sex Differences in AD/HD: Conference Summary. Journal of Abnormal Child Psychology, 24, Barkley, R. A. (1996a). Attention-Deficit/Hyperactivity Disorder. In E. J. Mash & R. A. Barkley (Eds.), Child Psychopathology (pp ), New York, Guilford.

6 306 P. Magnússon et al. Scand J Psychol 40 (1999) Barkley, R. A. (1996b). Manual to accompany the workshop on attention deficit/hyperacti ity disorder in children and adults. Workshop manual. Barkley, R. A., DuPaul, G. J. & McMurray, M. B. (1991). Attention deficit disorder with and without hyperactivity: Clinical response to three dose levels of methylphenidate. Pediatrics, 87, Baumeister, J. J., Alegría, M., Bird, H. R., Rubio-Stipec, M. & Caniono, G. (1992). Are attentional-hyperactivity deficits unidimensional or multidimensional syndromes? Empirical findings from a community survey. Journal of the American Academy of Child and Adolescent Psychiatry, 31, Baumeister, J. J., Bird, H. R., Caniono, G., Rubio-Stipec, M., Bravo, M. & Alegría, M. (1995). Dimensions of attention deficit/hyperactivity disorder: Findings from teacher and parent reports in a community sample. Journal of Clinical Child Psychology, 24, Baumgaertel, A., Wolraich, M. L. & Dietrich, M. (1995). Comparison of diagnostic criteria for attention deficit disorders in a German elementary school sample. Journal of the American Academy of Child and Adolescent Psychiatry, 34, Cantwell, D. P. (1996). Attention deficit disorder: A review of the past 10 years. Journal of the American Academy of Child and Adolescent Psychiatry, 35, Crijnin, A. A. M., Achenbach, T. M. & Verhulst, F. C. (1997). Comparisons of problems reported by children in 12 cultures: Total problems, externalizing and internalizing. Journal of the American Academy of Child and Adolescent Psychiatry, 36, DuPaul, G. J. (1991). Parent and teacher ratings of AD/HD symptoms: Psychometric properties in a community-based sample. Journal of Clinical Child Psychology, 20, DuPaul, G. J., Anastopoulos, A. D., Power, T. J., Reid, R., Ikeda, M. J. & McGoey, M. J. (1998). Parent ratings of Attention- Deficit/Hyperactivity Disorder: Factor structure, normative data, and psychometric properties. Journal of Psychopathology and Beha ioral Assessment, 20, DuPaul, G. J., Power, T. D., Anastopoulos, A. D., Reid, R., McGoey, M. J. & Ikeda, M. J. (1997). Teacher ratings of Attention-Deficit/Hyperactivity Disorder: Factor structure, normative data, and psychometric properties. Psychological Assessment, 9, Gaub, M. & Carlson, C. L. (1997). Behavioural characteristics of DSM-IV ADHD subtypes in a school-based population. Journal of Abnormal Child Psychology, 25, Hannesdóttir, H. & Einarsdóttir, S. (1995). The Icelandic Child Mental Health Study. An epidemiological study of Icelandic children 2 18 years of age using the Child Behavior Checklist as a screening instrument. European Child and Adolescent Psychiatry, 4, Hart, E. L., Lahey, B. B., Loeber, R., Applegate, B. & Frick, P. J. (1995). Developmental change in attention-deficit/hyperactivity disorder in boys: A four year longitudinal study. Journal of Abnormal Child Psychology, 23, Healy, J. M., Newcorn, J. H., Halperin, J. M., Wolf, L. E., Pascualvaca, D. M., Scmeidler, J. & O Brien, J. D. (1993). The factor structure of AD/HD items in DSM-III-R: Internal consistency and external validation. Journal of Abnormal Child Psychology, 21, Kadesjö, B. & Gillberg, C. (1998). Attention deficits and clumsiness in Swedish 7-year-old children. De elopmental Medicine and Child Neurology, 40, Lahey, B. B. & Carlson, C. L. (1991). Validity of the diagnostic category of attention deficit disorder without hyperactivity: A review of the literature. Journal of Learning Disabilities, 24, Reid, R. (1995). Assessment of ADHD with culturally different groups: the use of behavioral rating scales. School Psychology Re iew, 24, Reid, R., DuPaul, G. J., Power, T. J., Anastopoulos, A. D., Rogers-Atkinson, D., Noll, M-B. & Riccio, C. (1998). Assessing culturally different students for attention deficit hyperactivity disorder using behavior rating scales. Journal of Abnormal Child Psychology, 26, Shaffer, D., Fisher, P., Dulcan, M. K., Davies, M., Piacentini, J., Schwab-Stone, M. E., Lahey, B. B., Bourdon, K., Jensen, P. S., Bird, H. R., Canino, G. & Regier, D. A. (1995). The NIMH Diagnostic Interview Schedule for Children version 2.3 (DISC- 2.3): Description, acceptability, prevalence rates and performance in the MECA study. Journal of the American Academy of Child and Adolescent Psychiatry, 35, Vignisson, E. (1995). Athugun á pròffræðilegum eiginleikum of irknilista DuPaul [Psychometric assessment of DuPaul s hyperacti ity checklist]. Unpublished thesis at the Faculty of Social Science at the University of Iceland. Weisz, J. R., & Eastman, K. L. (1995). Cross-national research on child and adolescent psychopathology. In F. C. Verhulst and H. M. Koot (Eds.), The epidemiology of child and adolescent psychopathology (pp 42 65). Oxford Medical Publications. Wolraich, M. L., Hannah, J. N., Pinnock, T. Y., Baumgaertel, A. & Brown, J. (1996). Comparison of diagnostic criteria for attention deficit hyperactivity disorder in a county-wide sample. Journal of the American Academy of Child and Adolescent Psychiatry, 35, Received 16 September 1998, accepted 6 April 1999