ADHD is a neurodevelopmental disorder most frequently

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1 / ARTICLE Journal Magnússon of Attention et al. / Validity Disorders of Adult Rating Scales Validity of Self-Report and Informant Rating Scales of Adult ADHD Symptoms in Comparison With a Semistructured Diagnostic Interview Journal of Attention Disorders Volume 9 Number 3 February Sage Publications / hosted at Páll Magnússon Landspítali University Hospital, Reykjavík Jakob Smári University of Iceland, Reykjavík Dagbjörg Sigurðardóttir Gísli Baldursson Landspítali University Hospital, Reykjavík Jón Sigmundsson Kristleifur Kristjánsson decode Genetics, Reykjavík Solveig Sigurðardóttir Stefán Hreiðarsson Steingerður Sigurbjörnsdóttir State Diagnostic and Counseling Center, Kópavogur Ólafur Ó. Guðmundsson Landspítali University Hospital, Reykjavík In a study of ADHD symptoms in the relatives of probands diagnosed with ADHD, the validity of self-reported and informantreported symptoms in childhood and adulthood was investigated with a semistructured diagnostic interview, the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS) adapted for adults, as a criterion. The participating relatives were 80 women and 46 men aged 17 to 77. Rating scales based on the Diagnostic and Statistical Manual of Mental Disorders (4th ed.) were completed by participants and informants. Internal consistency of the scales and interrater reliabilities of the diagnostic interview were satisfactory. Correlations between ratings across sources of information supported convergent and divergent validity. Self-report scales and informant scales predicted interview-based diagnoses in childhood and adulthood with adequate sensitivities and specificities. It was concluded that the rating scales have good psychometric properties, at least in at-risk populations. (J. of Att. Dis. 2006;9(3) ) Keywords: adult ADHD; relatives; rating scales; K-SADS ADHD is a neurodevelopmental disorder most frequently diagnosed in childhood. A number of studies has demonstrated high rates of persistence of the symptoms of the disorder into adulthood (Barkley, Fischer, Smallish, & Fletcher, 2002), emphasizing the necessity for reliable and valid instruments for the assessment of these symptoms in adults. The present study was conducted in the context of an investigation into the genetics of ADHD. For the purpose of the genetic study, reliable and valid instruments were Authors Note: Address correspondence to Páll Magnússon, Dept. of Child and Adolescent Psychiatry, Landspítali University Hospital, Dalbraut 12, 105 Reykjavík, Iceland; pama@ landspitali.is. 494

2 Magnússon et al. / Validity of Adult Rating Scales 495 needed to assess phenotypic variations in symptoms of hyperactivity/impulsivity and inattention in the adult relatives of probands with ADHD. Although the diagnosis of ADHD in childhood is relatively well established within the frame of reference of the fourth edition of Diagnostic and Statistical Manual of Mental Disorders (DSM-IV; American Psychiatric Association, 1994), several problems have been highlighted in discussions about the assessment and diagnosis of ADHD in adulthood. First, from a developmental perspective (Murphy & Barkley, 1996), doubts have been cast on the validity of the symptom thresholds defined in DSM-IV for diagnosing adult ADHD. The definition of these thresholds was based on field trials using a sample of children and adolescents 4 to 17 years of age (Lahey et al., 1994). This has led some researchers to argue for the use of a dimensional approach in diagnosing the disorder in adults instead of a criterion-referenced diagnosis (Barkley, 1998; Faraone, Biederman, Feighner, & Monuteaux, 2000; Murphy & Barkley, 1996). Another question raised is whether the behavioral criteria described in DSM-IV, derived from research on ADHD in childhood, are sensitive measures of ADHD in adulthood (Faraone et al., 2000). The developmental course of different symptoms seems to be quite variable. For example, there is a greater attenuation of hyperactivity than of inattention symptoms with increasing age. A further point concerns the accuracy of recall of childhood symptoms. The issue is important because the presence of symptoms in childhood is a prerequisite for the diagnosis of ADHD in adulthood. Henry, Moffitt, Caspi, Langley, and Silva (1994) found that their participants recollections of their own hyperactivity symptoms correlated weakly with ratings collected in childhood from parents and teachers and with the participants own reports in childhood. The results of a recent follow-up study (Barkley et al., 2002) were slightly more encouraging, although participants diagnosed with ADHD in childhood still tended to underreport their childhood symptoms when surveyed in young adulthood. In a recent study (Mannuzza, Klein, Klein, Bessler, & Shrout, 2002) of the accuracy of adult recollection of childhood ADHD symptoms, the authors found that in general population surveys, adult self-reports of childhood behavior were unlikely to yield valid diagnoses. However, the accuracy of such retrospective information was substantially higher in groups of adults expected to include a higher number of individuals with childhood ADHD. The authors suggested that future studies should focus on the incremental validity of reports from knowledgeable informants for retrospective diagnoses. In a study of the assessment of childhood and adult ADHD symptoms by adults self-ratings, Murphy and Schachar (2000) compared adult self-report of childhood symptoms with retrospective ratings of the participants childhood symptoms rated by their parents. The correlations between self- and informant ratings of childhood symptoms were significant (.69 to.79). Another group of adults provided self-ratings of current ADHD symptoms that were compared with ratings made by their partners. Ratings of current symptoms also correlated significantly (.59 to.70). The ratings were made with an 18-item DSM- IV based questionnaire. O Donnell, McCann, and Pluth (2001) compared the self-ratings of current ADHD symptoms from a group of adult participants previously diagnosed with ADHD with self-ratings made by a matched group of control participants. The results indicated that participants endorsing ADHD symptoms were highly likely to have been previously diagnosed with ADHD. Mehringer et al. (2002) reported a preliminary validation of a brief DSM-IV based self-rating scale that was compared with an external gold standard (semistructured clinical interview). The group of participants studied was known to have a high rate of ADHD. The results indicated a sensitivity of.80 and a specificity of.60. Mehringer et al. (2002) used a semistructured clinical interview to generate DSM-III-R diagnoses in adults. Other researchers have used the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS) interview (Kaufman et al., 1997) adapted for use with adults to diagnose ADHD (Biederman et al., 1995; Spencer et al., 2001). In a reanalysis of data on 719 adults aged 17 to 84 who were applying for a driving license, Murphy, Gordon, and Barkley (2000) found that some symptoms of ADHD were extremely common on self-report rating scales and concluded that it was highly important to triangulate such information with other data before attributing ADHD diagnoses. A similar conclusion was reached by Lewandowski et al. (2000), who collected rating scale data on 373 college students. A general discussion of this issue is presented in Murphy and Adler (2004) where the authors urged caution in relying on rating scales in the diagnosis of ADHD. The objectives of the present study were to evaluate the validity of brief DSM IV-based questionnaires of current and retrospective informant-based and self-reported ADHD symptoms by comparing the ratings of different raters among themselves and with a semistructured interview.

3 496 Journal of Attention Disorders Participants Method The 126 participants, 80 women and 46 men, were the relatives of 48 children and adolescents diagnosed with ADHD. The age range was 17 to 77 years (M = 40.5, SD = 13.8). Of these participants, 82 were first-degree relatives, 39 were second-degree relatives, and 5 were thirddegree relatives. Mothers of probands proved to be more willing to participate in the study than fathers, 41 and 28, respectively. Measures The K-SADS diagnostic interview is originally a downward extension of the Schedule for Affective Disorders and Schizophrenia (Endicott & Spitzer, 1978). The diagnostic interview employed in the present study was an adaptation of the Present and Lifetime version of the K-SADS interview (Kaufman et al., 1997). In the present study, only the section for ADHD was used. Probes tapping childhood symptoms were worded in the past tense, and some probes for current symptoms were modified using examples of behavior more appropriate for adults. Instead of using skip-out questions in the manner conventional for this version of the K-SADS, the interviewers went through all the items of the ADHD section, which made it possible to generate a severity score instead of a categorical classification only. All 18 behavioral criteria were scored on a scale of 1, 2 or 3, where a score of 1 signified the absence of a symptom, a score of 2 signified a subthreshold symptom, and a score of 3 signified that a symptom was above the clinical threshold, frequently having a moderate to severe effect on functioning. This is of course probably best regarded as a rank order scale. Nevertheless, scores for DSM-IV defined symptom domains are summarized in the present study to generate a severity score of ADHD symptomatology (K-SADS severity score). This may be somewhat questionable, but it was considered to be important as a complement to a categorical approach that is purely based on the criteria of DSM-IV. To test the robustness of our approach, we formed new variables measuring the number of symptoms present corresponding to the symptom domains of inattention and hyperactivity/impulsivity as well as a total score. A symptom was scored present if it was rated 2 or 3 and absent if it was rated 1. The Pearson correlation coefficients between these variables and the K-SADS severity scores were all above.96. Consequently, the correlations between the symptom count variables and the rating scales were almost identical to the correlations we report between the K-SADS severity scores and the rating scales. This seems to justify treating the interview scales in the way we do in this study. In addition, we derived DSM-IV diagnoses of ADHD for childhood and adulthood from the K-SADS interviews using for childhood diagnoses the DSM-IV defined diagnostic threshold of at least six symptoms being present in either symptom domain. For diagnosis in adulthood, the requirement was made of at least one symptom above threshold (score of 3) in childhood and five symptoms above threshold (scores of 3) in either symptom domain in adulthood. This relaxation of the diagnostic thresholds in adulthood (five symptoms present instead of six) was based on the argument that diagnostic criteria derived from research on children are too strict when it comes to adults (Murphy & Barkley, 1996). To this modified version of the K-SADS we added 31 items collecting information about developmental, health, and school history as well as questions about the use of mental health services and medication. Functional impairment was assessed by the clinicians conducting the interviews on the basis of all the information gathered in the interviews. The questionnaire items were based on the 18 DSM-IV behavioral criteria for ADHD evaluated on a 4-point Likert scale (e.g., I am easily distracted never or rarely, sometimes, often, very often). The following four versions of the scale were employed: self-report of symptoms in adulthood (current), self-report of childhood symptoms, informant report of symptoms in adulthood (current), informant report of childhood symptoms. In the two versions evaluating symptoms in adulthood, the frame of reference was the participants behavior in the past 6 months. In the two versions for childhood symptoms, participants and informants were asked to report on behaviors in the age period 5 to 12 years. Although DSM-IV includes the criterion of onset before the age of 7, several authors have recommended a higher cutoff (Applegate et al., 1997; Barkley & Biederman, 1997; Willoughby, Curran, Costello, & Angold, 2000). Setting the upper limit at age 12 was considered to reduce the likelihood of missing potential cases (Mehringer et al., 2002). Procedure The study was conducted in the context of a research project on the genetics of ADHD. A list of probands was generated consisting of children and adolescents diagnosed with ADHD in a child and adolescent psychiatric clinic and in private practice by experienced child psychiatrists and neurodevelopmental pediatricians. The diag-

4 Magnússon et al. / Validity of Adult Rating Scales 497 noses were in all cases based on interviews with parents or caregivers where information was gathered on developmental and health history and behavioral symptoms. A medical examination was conducted, and standardized rating scales completed by parents and teachers provided further information. Parents of probands were contacted by letter, followed by a phone call. Appointments were made for diagnostic interviews for parents willing to participate, and screening questionnaires were sent by mail. The participants were asked to complete the self-report versions of the questionnaire themselves and to ask those they thought most knowledgeable about their current and childhood behavior to complete the two informant versions. In the first telephone contact with the participants they were encouraged to inquire among the proband s first-, second-, and third-degree relatives who would be willing to participate in the project. Contact was subsequently made with these relatives in accordance with the parents indications, and if they agreed to participate they received the questionnaires by mail and were given appointments for diagnostic interviews. The informants were in a large majority of cases spouses, parents, or siblings of the participants. In most cases, parents or siblings of participants filled in the childhood symptoms questionnaires and spouses or close friends provided the data on current symptoms. All participants brought the completed questionnaires with them when they came in for their appointments, but the clinicians conducting the interviews were kept blind to the results of the questionnaires. All the interviewers were clinicians (child psychiatrists, developmental pediatricians, and a clinical child psychologist) with long experience in the diagnosis and treatment of ADHD. Prior to starting the data collection, two training interviews were videotaped. The interviewers then scored them separately and reviewed their scores together, discussing all differences in scoring to reach a consensus. During the data collection, eight additional interviews were videotaped and scored separately by interviewers to evaluate interrater reliability. Statistical Analysis Alpha reliability was calculated for all scales and subscales and all kinds of raters. Interrater reliability was calculated with correlation coefficients based on all pairs of six raters rating eight randomly chosen ratees. Correlations were calculated between scores on all scales and subscales within and across raters. This was done for men and women separately. Receiver operating characteristic (ROC) analyses were conducted with ADHD diagnoses in childhood and adulthood as the state variables and selfreport and informant ratings in childhood and adulthood, Table 1 Means and Standard Deviations of All Rating Scales and Interview Severity Scores for Women (n = 80) and Men (n = 46) respectively, as the independent variables. Independent groups t tests were conducted for all scales with gender as the independent variable. Paired t tests were performed comparing self-ratings and informant ratings on all rating scales. Results Women Men M SD M SD IA interview scores childhood * 4.9 HI interview scores childhood * 5.2 Total interview scores childhood * 9.5 IA self-report childhood HI self-report childhood Total self-report childhood IA informant childhood HI informant childhood Total informant childhood IA interview scores adulthood HI interview scores adulthood Total interview scores adulthood IA self-report adulthood HI self-report adulthood Total self-report adulthood IA informant adulthood HI informant adulthood Total informant adulthood Note: IA = inattention symptoms; HI = hyperactivity/impulsivity symptoms. *p <.05 (two-tailed). Means and standard deviations were calculated for all scales and subscales for female and male participants and overall (see Table 1). The only significant differences between men and women were found in the diagnostic interview data concerning childhood for the overall ADHD symptoms and for the hyperactivity/impulsivity symptoms. The sample means were however higher for men than women in all cases. Means were compared between first-degree relatives, on one hand, and second- and third-degree relatives, on the other hand. In all cases, the sample means were higher for the first-degree relatives. The differences were significant only for the total score and the inattention subscale for self-report of childhood symptoms.

5 498 Journal of Attention Disorders Table 2 Coefficients Alpha of All Rating Scales and Interview Severity Scores for Women (n = 80) and Men (n = 46) Alpha coefficients were calculated for all scales for men and women separately (see Table 2). Interrater Reliability of the Semistructured Interviews Women Men IA interview scores childhood HI interview scores childhood Total interview scores childhood IA self-report childhood HI self-report childhood Total self-report childhood IA informant childhood HI informant childhood Total informant childhood IA interview scores adulthood HI interview scores adulthood Total interview scores adulthood IA self-report adulthood HI self-report adulthood Total self-report adulthood IA informant adulthood HI informant adulthood Total informant adulthood Note: IA = inattention symptoms; HI = hyperactivity/impulsivity symptoms. To assess interrater reliabilities for the severity scores based on the diagnostic interviews, videotaped interviews with 8 randomly selected participants were independently rated the by six raters. Both Pearson and Spearman correlations were calculated for each pair of raters across the 8 participants and a mean for all pairs calculated for each scale. This was done for inattention scores, hyperactivity/impulsivity scores, and total scores both in adulthood and childhood. The results were as follows (with first the minimum value then the maximum value and then the mean value): inattention in adulthood (Pearson 0.92/0.99, 0.97; Spearman 0.42/0.99, 0.72), hyperactivity/impulsivity in adulthood (Pearson 0.99/ 1.00, 0.99; Spearman 0.76/1.00, 0.87), total score in adulthood (Pearson 0.97/0.998, 1.00, Spearman 0.57/ 0.99, 0.72), inattention in childhood (Pearson 0.96/1.00, 0.98, Spearman 0.72/1.00, 0.88), hyperactivity/ impulsivity in childhood (Pearson 0.95/1.00, 0.98; Spearman 0.76/1.00, 0.85), total score in childhood (Pearson 0.98/1.00, 0.99, Spearman 0.72/1.00, 0.88). Consistency between self-reports, ratings of informants, and interview severity scores for childhood symptoms. Correlations were calculated for childhood symptoms between self-reported symptoms, ratings of informants, and interview severity scores for symptoms overall as well as for inattention and hyperactivity/ impulsivity symptoms separately. This was done for men and women separately (see Table 3). When we look at the correlations between total scores on the diagnostic interview, self-ratings, and informant ratings, the coefficients vary between.58 and.78 for women and between.49 and.80 for men. In both cases, the highest correlations are between the interview severity scores and self-report. When we look at the specificity in the relationships between symptom domains or subscales, in most cases ratings of inattention have stronger relationships (i.e., stronger sample correlations) with other ratings of inattention than with ratings of hyperactivity/impulsivity, and similarly, ratings of hyperactivity/impulsivity have stronger relationships within themselves than with ratings of inattention. The only exception is that for women, symptoms of inattention based on the interview have a stronger relationship with self-reported hyperactivity/impulsivity ratings than with self-reported inattention ratings. Informant and self-report ratings for childhood symptoms were compared with repeated measures t tests. This was done for inattention symptoms, hyperactivity/ impulsivity symptoms, and symptoms overall. In all cases, self-ratings were significantly higher than informant ratings (p <.01). Consistency between self-reports, ratings of informants, and interview severity scores for symptoms in adulthood. Correlations were calculated for current symptoms between self-reports, ratings of informants, and interview scores. This was done for symptoms overall and for inattention and hyperactivity/impulsivity symptoms separately. Ratings for men and women were analyzed separately (see Table 4). For correlations between total scores on the diagnostic interview, self-ratings, and observer ratings, the coefficients vary between.55 and.83 for women and between.50 and.78 for men. In both cases, as for childhood symptoms, the highest correlations are between the diagnostic interview and self-report. When we look at the specificity in the relationships between symptom domains or subscales, ratings of inattention have in all cases stronger relationships (that is, stronger sample correlations) with other ratings of inattention than with ratings of hyperactivity/impulsivity, and similarly, ratings

6 Magnússon et al. / Validity of Adult Rating Scales 499 Table 3 Correlations Between Self-Reported Symptoms, Informant-Reported Symptoms, and Interview Severity Scores of IA Symptoms, HI Symptoms, and Total ADHD Symptoms in Childhood Total interview scores IA interview scores HI interview scores Total symptoms self-report IA symptoms self-report HI symptoms self-report Total symptoms informant IA symptoms informant HI symptoms informant Note: Above diagonal, women (n = 80); below diagonal, men (n = 46). IA = inattention symptoms; HI = hyperactivity/impulsivity symptoms. For all correlations, women, p <.01; for all correlations, men, p <.05 (two-tailed tests). Table 4 Correlations Between Self-Reported Symptoms, Informant-Reported Symptoms, and Interview Severity Scores of IA Symptoms, HI Symptoms, and Total ADHD Symptoms in Adulthood Total interview scores IA interview scores HI interview scores Total symptoms self-report IA symptoms self-report HI symptoms self-report Total symptoms informant IA symptoms informant HI symptoms informant.45.28* Note: Above diagonal, women (n = 80); below diagonal, men (n = 46). IA = inattention symptoms; HI = hyperactivity/impulsivity symptoms. For all correlations, women, p <.01; for all correlations men, except one, p <.05. *p >.05. of hyperactivity/impulsivity have stronger relationships within themselves than with ratings of inattention. Informant and self-report ratings for symptoms in adulthood were compared with repeated measures t tests. This was done for inattention symptoms, hyperactivity/ impulsivity symptoms, and symptoms overall. In all cases but one (inattention), self-ratings were significantly higher than informant ratings (p <.05). Prediction of ADHD Diagnoses According to the K-SADS interview, 10 participants fulfilled diagnostic criteria for ADHD in childhood (5 with ADHD combined type and 5 with the inattentive type). ROC curves were plotted to assess the ability of the questionnaires to predict diagnoses in childhood and adulthood. The numerical values are given in Table 5. In the assessment of the prediction of childhood diagnosis by the self-report questionnaire for childhood symptoms, the area under the curve (AUC) was.94 (95% CI =.87, 1.00). A cutoff of 25.8 points for childhood symptoms corresponded to a sensitivity of.80 and a specificity of.92. A ROC analysis was also conducted for the ability of the self-report questionnaire of current symptoms to predict a current diagnosis of ADHD. For this purpose, the DSM-IV diagnostic threshold that six out of nine symptoms of either or both inattention or hyperactivity/impulsivity should be present was lowered to five out of nine. According to this threshold, 5 participants were categorized as affected. The AUC was.95 (95% CI =.88, 1.00), and a cutoff score of 32.5 points gave a sensitivity of.80 and a specificity of.98. A similar analysis was conducted with informant ratings as the predictor. When

7 500 Journal of Attention Disorders Table 5 Sensitivity and Specificity of Childhood and Adulthood Self-Report and Informant Scales in Predicting Diagnoses of ADHD in Childhood and Adulthood Predictors and Diagnoses Cutoff Score Sensitivity Specificity Self-report ratings of childhood symptoms predicting a childhood diagnosis of ADHD Informant ratings of childhood symptoms predicting a childhood diagnosis of ADHD Self-report ratings of symptoms in adulthood predicting a diagnosis of ADHD in adulthood Informant ratings of symptoms in adulthood predicting a diagnosis of ADHD in adulthood ADHD diagnosis in childhood was predicted from informant childhood ratings, the AUC was.90 (95% CI =.82,.97), and a cutoff score 9.1 corresponded to a sensitivity of.90 and a specificity of.55. When current ADHD diagnosis was predicted from informant ratings of current symptoms, the AUC was.90 (95% CI =.82,.97), and a cutoff score of 14.1 corresponded to a sensitivity of.80 and a specificity of.85. Relationships Between Symptoms Over Time Within Method and Type of Informant To investigate the stability of ADHD symptoms over time, we calculated correlations between childhood symptoms and current symptoms for the interview scores, self-report, and informant ratings (see Table 6). For self-reported symptoms and symptoms based on the diagnostic interview, the relationships between current and childhood symptoms were strong. For symptoms rated by informants, the relationships were much weaker. This was especially true for men and symptoms of inattention. It is noteworthy that the pattern of correlations is consistent with at least some specificity in the ratings of symptoms of inattention and hyperactivity/impulsivity. Discussion The use of diagnostic interviews in research focusing on ADHD symptomatology is often cumbersome. Thus, it is very important if information gathered with rating scales is found to be sufficiently reliable and valid for initial screening. The aim of the present study was to investi-

8 Magnússon et al. / Validity of Adult Rating Scales 501 Table 6 Correlations Between Symptoms in Childhood and Adulthood for Interview Severity Scores, Self-Report, and Informant Scales Adult IA Adult HI Adult Total Women Men Women Men Women Men Interview Childhood IA Childhood HI Childhood total Self-report Childhood IA Childhood HI Childhood total Informant Childhood IA.53.22*.47.25*.54.27* Childhood HI.42.26* Childhood total.48.26* Note: IA = inattention symptoms; HI = hyperactivity/impulsivity symptoms. *p >.05 (two-tailed); all other correlations significant at p <.05 at least. gate the psychometric properties of self- and informantbased rating scales of DSM-IV defined ADHD symptoms, using a semistructured interview as a criterion of concurrent validity. In this study of relatives of probands diagnosed with ADHD, we addressed the consistency of ADHD symptomatology as measured with diagnostic interviews, self-report, and ratings of participants by other family members. This was done with regard to retrospective recall of childhood symptoms as well as ratings of symptoms in adulthood. Means for self-reported symptoms and informant ratings were somewhat higher than what has been observed in previous studies using similar instruments in normal adult populations (Murphy & Schachar, 2000). This is what might be expected given that our sample consisted of relatives of probands with ADHD. Means for self-reported symptoms in childhood were significantly higher than informant ratings. This is in accordance with results reported by Murphy and Schachar (2000) but in contrast with the results reported by Zucker, Morris, Ingram, Morris, and Bakeman (2002). Self-reported ratings of symptoms in adulthood were similarly higher than informant ratings for hyperactivity/ impulsivity and symptoms overall. This is in contrast with Murphy and Schachar and Zucker et al. In general, the psychometric properties of the interview severity scores, the self-reports, and the informant ratings were excellent. First, the alpha coefficients of internal consistency were high for all scales for both sexes and both childhood and current symptoms. The lowest values were around.80. Furthermore, the interrater reliabilities of the diagnostic interview scores for all scales based on a small subsample were satisfactory. Third, there was in general a fair consistency within scales across source of information and method, the lowest correlations between corresponding scales were around.45, and most of them were substantially higher. The lowest correlations were between interview ratings and informant ratings, that is, when both source of information and method were different. The correlations are in general slightly higher than for example in Zucker et al. (2002), who studied a sample of college students presenting with academic difficulties. There was some support for the divergent validity of measures of inattention and hyperactivity/ impulsivity as sample correlations for noncorresponding scales were almost in all cases lower than between corresponding scales. Finally, there was good consistency in ratings on corresponding measures across time frames (childhood/adulthood). Furthermore, some support for divergent validity was found as correlations across time for corresponding measures were in almost all cases higher than between noncorresponding measures. The validity of the rating scales was further supported by the fact that they predicted interview-generated diagnoses with a high degree of sensitivity and specificity. As to the limitations of the present study, the use of the diagnostic interview data deserves some comment. We summarized the scores on different items even though the items are rated on a rank order rather than an interval scale. This was done to avoid the limitations of a categorical, diagnosis-centered approach and thus to retain more of the potentially discriminating information in the interview data. Well aware of some possibly questionable assumptions involved in our approach, we do not think they compromise our interpretation of the relationships between the diagnostic interview data and self-report and informant rating scales as informative with regard to the validity of the rating scales. As already mentioned, these assumptions seem to be justified by the extremely high correlations between the interview scales and variables based on a count of symptoms present. It further supported the validity of the rating scales that they showed good prediction of ADHD diagnoses both in childhood and for the current situation, even though it must be taken into account that the number of participants satisfying DSM-IV criteria in the sample was rather slight. A possible reason is that the diagnostic thresholds determined on the basis of research on children and adolescents may be too high. Another possible reason is that in the diagnostic interviews the impairment criteria implicit in the scor-

9 502 Journal of Attention Disorders ing of the K-SADS requiring moderate to severe effect on functioning for many behavioral symptoms were applied quite strictly. Many of the participants had developed strategies to contain the negative effects of their symptoms, such as the extensive use of daily planners and reminder systems, and were able to function quite adequately with the aid of such supportive devices. It is concluded that the rating scales investigated are reliable and valid at least in at-risk populations. Reliable and valid self-report questionnaires may be especially important in data collection for research purposes, but it should be noted that in clinical work, where decisions need to be made about individual cases, nothing can supplant thorough clinical interviews and information collected from several sources. References American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author. Applegate, B., Lahey, B. B., Hart, E. L., Biederman, J., Hynd, G. W., Barkley, R. A., et al. (1997). Validity of the age-of-onset criterion for ADHD: A report from the DSM-IV field trials. Journal of the American Academy of Child and Adolescent Psychiatry, 36, Barkley, R. A. (1998). Attention deficit/hyperactivity disorder: A handbook for diagnosis and treatment. New York: Guilford. Barkley, R. A., & Biederman, J. (1997). Toward a broader definition of the age-of-onset criterion for attention-deficit hyperactivity disorder. Journal of the American Academy of Child and Adolescent Psychiatry, 36, Barkley, R. A., Fischer, M., Smallish, L., & Fletcher, K. (2002). The persistence of attention-deficit/hyperactivity disorder into young adulthood as a function of reporting source and definition of disorder. Journal of Abnormal Psychology, 111, Biederman, J., Wilens, T., Mick, E., Milberger, S., Spencer, T. J., & Faraone, S. V. (1995). Psychoactive substance use disorders in adults with attention deficit hyperactivity disorder (ADHD): Effects of ADHD and psychiatric comorbidity. American Journal of Psychiatry, 152, Endicott, J., & Spitzer, R. L. (1978). A diagnostic interview: The Schedule for Affective Disorders and Schizophrenia. Archives of General Psychiatry, 35, Faraone, S. V., Biederman, J., Feighner, J. A., & Monuteaux, M. C. (2000). Assessing symptoms of attention deficit hyperactivity disorder in children and adults: Which is more valid? Journal of Consulting and Clinical Psychology, 68, Henry, B., Moffitt, T. E., Caspi, A., Langley, J., & Silva, P. A. (1994). On the remembrance of things past : A longitudinal evaluation of the retrospective method. Psychological Assessment, 6, Kaufman, J., Birmaher, B., Brent, D., Rao, U., Flynn, C., Moreci, P., et al. (1997). Schedule for Affective Disorders and Schizophrenia for School-Age Children Present and Lifetime version (K-SADS- PL): Initial reliability and validity data. Journal of the American Academy of Child and Adolescent Psychiatry, 36, Lahey, B. B., Applegate, B., McBurnett, K., Biederman, J., Greenhill, L., Hynd, G. W., et al. (1994). DSM-IV field trials for attention deficit hyperactivity disorder in children and adolescents. American Journal of Psychiatry, 151, Lewandowski, L., Codding, R., Gordon, M., Marcoe, M., Needham, L., & Rentas, J. (2000). Self-reported LD and ADHD symptoms in college students, The ADHD Report, 8(6), 1-4. Mannuzza, S., Klein, R. G., Klein, D. F., Bessler, A., & Shrout, P. (2002). Accuracy of recall of childhood attention deficit hyperactivity disorder. American Journal of Psychiatry, 159, Mehringer, A. M., Downey, K. K., Schuh, L. M., Pomerleau, C. S., Snedecor, S. M., & Schubiner, H. (2002). The assessment of hyperactivity and attention: Development and preliminary validation of a brief self-assessment of adult ADHD. Journal of Attention Disorders, 5, Murphy, K. R., & Adler, L. A. (2004). Assessing attention deficit/ hyperactivity disorder in adults: Focus on rating scales. Journal of Clinical Psychiatry, 65(Suppl. 3), Murphy, K., & Barkley, R. A. (1996). Prevalence of DSM-IV symptoms in adult licensed drivers: Implications for clinical diagnosis. Journal of Attention Disorders, 1, Murphy, K., Gordon, M., & Barkley, R. (2000). To what extent are ADHD symptoms common? A reanalysis of standardization data from a DSM-IV checklist. The ADHD Report, 8(3), 1-5. Murphy, P., & Schachar, R. (2000). Use of self-ratings in the assessment of symptoms of attention deficit hyperactivity disorder in adults. American Journal of Psychiatry, 157, O Donnell, J. P., McCann, K. K., & Pluth, S. (2001). Assessing adult ADHD using a self-report symptom checklist. Psychological Reports, 88, Spencer, T. J., Biederman, J., Faraone, S. V., Mick, E., Coffey, B., Geller, D., et al. (2001). Impact of tic disorders on ADHD outcome across the life cycle: Findings from a large group of adults with and without ADHD. American Journal of Psychiatry, 158, Willoughby, M. T., Curran, P. J., Costello, J., & Angold, A. (2000). Implications of early versus late onset of attention deficit/ hyperactivity disorder symptoms. Journal of the American Academy of Child and Adolescent Psychiatry, 39, Zucker, M., Morris, M. K., Ingram, S. M., Morris, R. D., & Bakeman, R. (2002). Concordance of self and informant ratings of adults current and childhood attention deficit/hyperactivity disorder symptoms. Psychological Assessment, 14, Páll Magnússon trained as a clinical psychologist at the Université René Descartes-Sorbonne and the Hopital de la Salpetriere, Paris. He has been a clinical child psychologist in the Department of Child and Adolescent Psychiatry, Landspítali University Hospital, Reykjavík, since Research interests include the assessment and epidemiology of ADHD and autism spectrum disorders. Jakob Smári received a Ph.D. in psychology from the University of Stockholm in 1985 and has been professor of psychology at the University of Iceland since His main research interest is obsessive compulsive disorder. Dagbjörg Sigurðardóttir received her M.D. from the University of Iceland in She did her specialty training in general psychiatry and child and adolescent psychiatry at the University of Iowa Hospitals and Clinic, Iowa City, United States, graduating in She has served as a child and adolescent psychiatrist at the Landspítali University Hospital since 1999 and is a part-time teacher at the University of

10 Magnússon et al. / Validity of Adult Rating Scales 503 Iceland Faculty of Medicine. Research interests include the genetics of psychiatric disorders. Gísli Baldursson received his M.D. from the University of Iceland in He did his specialist training in general and child and adolescent psychiatry in Sweden and Reykjavík. He has been working at the Department of Child and Adolescent Psychiatry, Landspítali University Hospital, Reykjavík, since Research interests include the assessment, epidemiology, and treatment of ADHD. Jón Sigmundsson, M.D., is a pediatrician and a clinical geneticist (Diplomatee American Board of Pediatrics, 1998; Diplomatee as a clinical geneticist, American Board of Medical Genetics, 1999). Since 1999, he has worked in various hospitals and clinics in Iceland and at decode Genetics He is currently working in the Landspítali University Hospital, Department of Psychiatry, Reykjavík, Iceland. Kristleifur Kristjánsson is an M.D. from the University of Iceland since 1982 and subsequently did his training in pediatrics and molecular and clinical genetics at the Medical College of Georgia and Baylor College of Medicine, Houston, Texas, and , respectively. He is currently a clinical genetic consultant at the Children Hospital in Reykjavík, Iceland, and a senior director of medical informatics and clinical collaborations at decode Genetics Iceland. His research interest is in the field of the genetics of common disorders. Solveig Sigurðardóttir received the M.D. from the University of Iceland in Trained as a neurodevelopmental pediatrician at the Kennedy Krieger Institute in Baltimore in , Sigurðardóttir is a consulting pediatrician at the State Diagnostic and Counseling Center in Kopavogur, Iceland. Stefán Hreiðarsson received his MD from the University of Iceland in 1974 and was board certified by the American Board of Pediatrics in 1981 after three years of residency in USA. He was a fellow in developmental pediatrics and pediatric genetics at the Kennedy-Krieger Institute, Johns Hopkins Medical Institutions in Baltimore from 1979 to He has for the last 20 years been the medical director of the State Diagnostics and Counselling Center in Iceland. Steingerður Sigurbjörnsdóttir, M.D., M.P.H., is a pediatrician with a subspecialty in ambulatory pediatrics. She has been in private practice for 10 years where she has delivered special services to children and adolescents with developmental and behavioral difficulties. Ólafur Ó. Guðmundsson received his M.D. in 1986 at the University of Iceland, Faculty of Medicine. He did his specialist training in general and child and adolescent psychiatry in Lund, Sweden, and West Midlands, United Kingdom, and is head of the Department of Child and Adolescent Psychiatry, Landspítali University Hospital, Reykjavík, as well as locum lecturer in child and adolescent psychiatry, University of Iceland, Faculty of Medicine. Research interests include epidemiology and genetics of child psychiatric disorders.