Revisiting the Factor Structure of the Strengths and Difficulties Questionnaire: United States, 2001

Revisiting the Factor Structure of the Strengths and Difficulties Questionnaire: United States, 2001 WAYNE C. DICKEY, PH.D.,

AND

STEPHEN J. BLUMBERG, PH.D.

ABSTRACT Objective: The Strengths and Difficulties Questionnaire is a 25-item instrument developed to assess emotional and behavioral problems. The current study attempted to replicate previous European structural analyses and to describe the latent dimensions that underlie responses to the parent-reported version of the Strengths and Difficulties Questionnaire for a representative sample of U.S. children and adolescents. Method: Parents/guardians of a national probability sample of 9,574 children and adolescents 4 to 17 years of age were administered the Strengths and Difficulties Questionnaire to assess emotional and behavioral problems within the past 1 month. A principal components analysis was performed for replication purposes, and exploratory and confirmatory factor analyses were performed to extract the underlying factors. Results: The predicted five-component structure (emotional, hyperactivity, prosocial, peer, conduct) was not entirely confirmed. Some items intended to assess conduct problems were more closely related to hyperactivity, and some items intended to assess peer problems were more strongly correlated with emotional or prosocial problems. Factor analyses revealed a stable three-factor model consisting of externalization problems, internalization problems, and a positive construal factor. Conclusions: The current analyses suggest that U.S. parents may construe conduct problems and peer problems differently than do European parents. These cultural differences may affect the assessment of psychopathology for children. J. Am. Acad. Child Adolesc. Psychiatry, 2004;43(9):1159–1167. Key Words: questionnaire, reliability, psychopathology, factor structure.

The Strengths and Difficulties Questionnaire (SDQ) is a brief 25-item emotional and behavioral assessment questionnaire (Goodman, 1997). It was developed to generate scores for five domains of psychological adjustment among children and adolescents: hyperactivity-inattention, emotional symptoms, prosocial behavioral, conduct problems, and peer problems. The Accepted April 12, 2004. From the Division of Health Interview Statistics, National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, MD. Funding for this study was provided in part by the National Institute for Mental Health, National Institutes of Health. Appreciation is extended to Dr. Robert Goodman, Dr. Ronald Kessler, Ms. Karen Bourdon, and three anonymous reviewers for their comments on earlier versions of this manuscript. This study was completed during Dr. Dickey’s Association of Schools of Public Health (ASPH) Public Health Fellowship, which was supervised by Dr. Blumberg. Dr. Dickey is now with ACS Federal Healthcare, Inc. Correspondence to Dr. Blumberg, National Center for Health Statistics, 3311 Toledo Road, Room 2112, Hyattsville, MD 20782; e-mail: sblumberg@ cdc.gov. 0890-8567/04/4309–1159©2004 by the American Academy of Child and Adolescent Psychiatry. DOI: 10.1097/01.chi.0000132808.36708.a9

items selected for each domain were based primarily on key symptoms for DSM-IV diagnoses (American Psychiatric Association, 1994), and their groupings were confirmed using multivariate structural analyses (Goodman, 1994, 2001). In general, the SDQ can be used as a screening tool for clinical assessment of mental disorders and for epidemiological research (Goodman et al., 2000a). Moreover, the instrument has been adapted for multiple informant reporting, including parent-report, teacher-report, and self-report. Additional information on the SDQ and copies of the instrument may be obtained on the Internet (www.sdqinfo.com). Research to date has supported the construct validity of the SDQ. For example, studies with European samples have found high correlations between the SDQ and the Rutter questionnaires (Elander and Rutter, 1995; Rutter, 1967), and the two sets of measures have been found to be comparable in discriminating psychiatric cases from noncases (Goodman, 1997). SDQ scores were also highly correlated with scores from the longer Child Behavior Checklist (CBCL)

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(Achenbach, 1991; Goodman and Scott, 1999; Koskelainen et al., 2000), and it was found to be better than the CBCL for identifying children with mental disorders (Klasen et al., 2000). Strong relationships were also observed between the SDQ self-report questionnaire and the Youth Self-Report (Achenbach and Edelbrock, 1987; Klasen et al., 2000; Koskelainen et al., 2000) and between individual subscales of the SDQ and independent clinical diagnosis in samples from England and Bangladesh (Goodman, 2001; Goodman et al., 2000b). Moreover, multi-informant SDQs were found to be relatively good screeners for conduct, hyperactivity, depressive, and anxiety disorders in a community sample from the 1999 British Child Mental Health Survey (Goodman et al., 2000a). A similar finding was observed within a Bangladeshi community (Mullick and Goodman, 2001). Like the Youth Self-Report, the SDQ contains several positively worded items assessing children’s strengths (e.g., “considerate of other people’s feelings,” “shares readily with other children”). The inclusion of these items helped to “modernize” this questionnaire by emphasizing desirable traits rather than focusing solely on deficits (Goodman, 1997). These items increased the acceptability of the instrument to parents. Relative to other related screening tools, the SDQ may also become more widely accepted by clinicians and researchers because it addresses contemporary issues such as impulsiveness, bullying, and having friends (Goodman, 1997). The five domains of psychological adjustment assessed by the parent-reported SDQ—four negative, one positive—were substantiated by Goodman (2001) using a nationwide sample of British children and adolescents. Similar analyses substantiating these five scales were reported for separate Swedish and German samples of children using the parent-reported SDQ (Smedje et al., 1999; Woerner et al., 2002). Yet, there are no published reports documenting the dimensional properties of the parent-reported SDQ for children and adolescents in the United States. With SDQ data for a large representative sample of U.S. children and adolescents, the current study first attempted to replicate the results of the structural analyses that substantiated the structural validity of the five scales. These previous structural analyses (Goodman, 2001; Smedje et al., 1999; Woerner et al., 2002) extracted 1160

five domains using principal components analysis (PCA). Principal components are weighted sums of the observed item-level data, and PCAs are generally used to identify a limited number of components that can best account for the total variance (including unique, common, and error variance) among a greater number of items. However, these linear composites of observed variables are not latent. That is, these composites do not necessarily reveal the unobserved attitudes or beliefs that hypothetically lead to the observed item-level responses. Exploratory factor analyses (EFAs) can be used to identify the limited number of underlying dimensions (i.e., factors) that best account for the variability in observed responses. EFA differs from PCA because the former is limited to the common or shared variance among the items (McDonald, 1985). In other words, with its focus on latent constructs that are presumed to be free of measurement error, EFA attempts to identify factors that explain only the interitem correlations rather than the total variance (including measurement error). The previous structural analyses used VARIMAX rotation to transform the component solution into a simpler structure that could be more easily interpreted. This rotation technique specifies that components must be orthogonal (i.e., uncorrelated). However, it is unlikely that the emotional and behavioral constructs underlying the SDQ data are uncorrelated. Indeed, Goodman (2001) reported cross-scale correlations (based on unweighted sums of the observed item-level data) that exceeded 0.5 in some comparisons. Rotation techniques have been developed that do permit components and factors to be correlated if those correlations produce a simpler, more interpretable structure. For example, PROMAX rotation (Hendrickson and White, 1964) is an oblique rotation technique that still maintains the VARIMAX goal of maximizing the extent to which the variance is spread among the factors but allows the factors to be correlated. Given these limitations in the previous analyses, the current study conducted further structural analyses to more closely examine the underlying structure of U.S. parents’ responses. EFAs were conducted using half of the U.S. sample, and the stability of the solution was explored using a confirmatory factor analysis (CFA) with the remaining half of the sample.

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METHOD

Statistical Analysis

Sample

All structural analyses were performed using SAS version 8.01. The first structural analysis was identical to previous analyses with the SDQ (Goodman, 2001; Smedje et al., 1999; Woerner et al., 2002). That is, the component structure of the SDQ was examined through the use of PCA of a matrix of correlations of all 25 items, with VARIMAX rotation to identify the simplest structure. The optimal number of components was selected based on the size of each eigenvalue; no eigenvectors with eigenvalues less than 1 were selected (Kaiser, 1960) because these components would represent less total variability than any single item in the scale. Next, the factor structure of the 25 SDQ items was examined using unweighted least-squares EFA and a polychoric correlation matrix. Unique variance was removed from the analysis by setting the diagonal of the correlation matrix to the estimated communality of each SDQ item (i.e., the squared multiple correlation of that item with all remaining items). PROMAX rotation was applied to the solution. The guidelines for selecting the optimal number of factors were the same as that used in the previous PCA. The child and adolescent sample data were randomly split in half, and the EFA was conducted on data from only one half of the sample (n = 4,773). Finally, the fit of the data to the model suggested by the EFA was explored using unweighted least-squares CFA with polychoric correlations. For the CFA, the factor structure was confirmed with the data from the half-sample not used for the EFA (n = 4,804). The CFA differed from the EFA in that standardized regression coefficients with an absolute value less than 0.3 in the EFA were fixed at zero in the CFA. The factors themselves, however, were permitted to correlate. Model fit was determined using the root-mean-square residual (RMR) and the Goodness of Fit Index (GFI) of Bentler and Bonett (1980). Because of the uncertain impact of using ordinal data, the commonly used χ2 statistic was not used to evaluate the overall fit of the model. The complex sampling design of the National Health Interview Survey includes clustering, stratification, and an oversample of African-American and Hispanic households. Sampling weights are critical for calculating prevalence rates. However, because the underlying structure of responses to a multi-item scale are less likely to be affected by the sampling procedures and because no fit statistics exist that account for sampling procedures, structural analyses were conducted using unweighted data. (It should be noted that ad hoc exploratory analyses with weighted data revealed no meaningful differences from the analyses with unweighted data.)

The National Health Interview Survey is an annual multistage probability household survey that collects comprehensive healthrelated information from a large sample of households representing the civilian, noninstitutionalized household population of the United States. Conducted by the National Center for Health Statistics of the Centers for Disease Control and Prevention, the face-to-face survey interview is administered by trained field representatives from the United States Bureau of the Census. One child younger than 18 years of age was randomly selected from each family with children for a supplemental interview that, in 2001, included the SDQ for children and adolescents between 4 and 17 years of age. The respondent was the adult parent/guardian of the randomly selected child. The response rate for the supplemental child interview was 80.6%. Approximately 92.4% of the 10,367 selected children aged 4 to 17 years with complete interviews had complete SDQ data (n = 9,577) and are included in the current analyses. Strengths and Difficulties Questionnaire The SDQ includes 25 items intended to measure various attributes of emotional and behavioral problems and an extended set of items to measure perceived difficulties, impact, and burden associated with emotional and behavioral problems. The current analyses focus solely on the 25 attribute items. Responses to each of the 25 items consisted of three options: not true, somewhat true, or certainly true. Several items were modified from the British English to assist content understanding among U.S. respondents: • “often has temper tantrums or hot tempers” was changed to “often loses temper” • “tends to play alone” was changed to “prefers to play alone” • “generally obedient and usually does what adults request” was changed to “generally well-behaved and usually does what adults request” • “down-hearted” was changed to “depressed” • “volunteers to help others” was changed to “offers to help others” • “sees work through to the end” was changed to “sees chores and homework through to the end” In addition, slight changes in wording were required to accommodate appropriateness according to age groups (ages 4–11 versus ages 12–17). For older children: • “other children” was changed to “other youth” • “[shares] toys, treats, pencils” was changed to “[shares] CDs, games, food” • “rather solitary, prefers to play alone” was changed to “would rather be alone than with other teenagers” • “nervous or clingy in new situations” was changed to “nervous in new situations, easily loses confidence” This American English version has been referred to as the National Institute of Mental Health version of the SDQ (Goodman, 2001). Before statistical analyses, responses to the 15 items that were worded negatively were assigned scores of 2 for certainly true, 1 for somewhat true, and 0 for not true. Responses to the 10 items that were worded positively were scored in the reverse direction. Therefore, for all items, higher scores indicated more problematic attributes. As a result, the prosocial behaviors component that is usually presented positively (e.g., Goodman, 2001) was analyzed instead as a prosocial behavioral problems component.

RESULTS Principal Components Analysis

Five eigenvalues greater than 1 were observed (5.49, 2.13, 1.53, 1.10, and 1.07), suggesting that a fivecomponent solution would best explain the total variance. The standardized regression coefficients between each item and each component derived from a VARIMAX rotation of the first five principal components are given in Table 1. To ease interpretability, coefficients with an absolute value less than 0.3 are omitted. The results of the PCA reveal that the hyper-

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TABLE 1 Principal Components Analysis on Parent SDQ: National Health Interview Survey 2001

Total Variance Explained

Component 1 Hyperactivity-Inattention

Distractible Not persistent (persistent) Restless Fidgety Unreflective (reflective)

0.70 0.62 0.75 0.69 0.56

Component 2 Emotional Problems

Component 4 Conduct Problems

Component 5 Peer Problems

0.31

Fears Worries Clingy Unhappy Somatic

0.62 0.70 0.60 0.58 0.53

Unhelpful (helps out) Uncaring (caring) Inconsiderate (considerate) Unkind to kids (kind to kids) Selfish (shares) Lies Fights Temper Steals Disobedient (obedient)

Component 3 Prosocial Problems

0.31 0.63 0.66 0.55 0.61 0.56

0.30

0.64 0.53 0.31 0.66

0.47 0.37

0.47

Lacks a good friend (good friend) Unpopular (popular) Best with adults Solitary Bullied

0.51 0.56 0.74 0.59 0.34

Note: Rotated VARIMAX five-component solution. Coefficients less than ±0.3 were omitted. Maximum coefficient for each item in boldface type. Item names in parentheses reflect item wordings before reverse coding of the items. SDQ = Strengths and Difficulties Questionnaire.

activity-inattention, emotional symptoms, and prosocial problems components are identified by the items that were intended to represent those domains. However, the components representing conduct problems and peer problems were represented by fewer than the intended five items. Although the majority of conduct items were related to the conduct dimension, a few items were also related to other components. Specifically, the lies and temper items were related to both the conduct component and the hyperactivity component, with the temper item related more strongly to the latter than to the former. The disobedient item, which is intended to relate to conduct problems, was instead related to the hyperactivity component and the prosocial problems component. 1162

The peer problems component was identified by only the best with adults and solitary items. The other items intended to represent peer problems were instead related to prosocial problems (lack of a good friend and unpopular) or to emotional problems (bullied). Exploratory Factor Analysis

Utilization of the eigenvalues greater than 1 rule revealed that three factors represented the optimal factor solution. The rotated matrix of standardized regression coefficients obtained from a PROMAX rotation of the first three factors revealed that one item (steals) was not related to any extracted factor. This judgment was based on the absolute values of the standardized regression coefficients, which were less than 0.3 with all three extracted factors. This suggests that answers to this

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item were not reliably associated with any of the three underlying factors that related to answers to the other SDQ items. As a result, data from that item were removed and the EFA was recalculated. Inspection of the eigenvalues from this final analysis still revealed a threefactor solution as optimal (eigenvalues for factors greater than 1 = 7.54, 2.02, 1.23). Table 2 presents the matrix of standardized regression coefficients for each SDQ item with each of the three factors after PROMAX rotation to ease interpretability. (Coefficients with an absolute value less than 0.3 were omitted.) Only one item (disobedient) had a regression coefficient greater than 0.3 with more than one extracted factor, which made interpretation easier. The prosocial problems items make up the bulk of the first factor, in addition to moderate relationships with the disobedient, lack of a good friend, and unpopular items. The second factor is moderately to strongly represented by all the hyperactivity items, and it has weak

to moderate relationships with the conduct items. Finally, the third factor has moderate to strong relationships with all the emotional problems items, and it has a weak to moderate association with the bullied, best with adults, and solitary items. Altogether, these factors may be interpreted as prosocial problems, externalization problems, and internalization problems. Factor scores based on these three factors were related. With correlated factors, some of the common variance explained by one factor will also be explained by another factor. Table 3 presents the correlations between the factors and the variance explained by each factor, computed with and without taking the other factors into account. Confirmatory Factor Analysis

The fit indices for the CFA confirmed the structure identified by the EFA. The RMR for the three-factor solution was 0.06, which is below the maximum value

TABLE 2 Exploratory Factor Analysis on Parent SDQ: National Health Interview Survey 2001 Factor 1 Prosocial Problems Distractible Not persistent (persistent) Restless Fidgety Unreflective (reflective)

Factor 2 Externalization Problems 0.72 0.64 0.80 0.72 0.64

Fears Worries Clingy Unhappy Somatic Unhelpful (helps out) Uncaring (caring) Inconsiderate (considerate) Unkind to kids (kind to kids) Selfish (shares) Lies Fights Temper Disobedient (obedient) Lacks a good friend (good friend) Unpopular (popular) Best with adults Solitary Bullied

Factor 3 Internalization Problems

0.63 0.68 0.48 0.65 0.48 0.67 0.75 0.58 0.72 0.59

0.49

0.44 0.31 0.48 0.38

0.64 0.67 0.36 0.45 0.49

Note: Rotated PROMAX three-factor solution. Coefficients less than ±0.3 were omitted. Item names in parentheses reflect item wordings before reverse coding of the items. SDQ = Strengths and Difficulties Questionnaire.

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TABLE 3 Interfactor Correlations and Variance Explained: Rotated PROMAX Three-Factor Solution

Correlation with factor 1 Correlation with factor 2 Reference axis correlation with factor 1 Reference axis correlation with factor 2 Unique common variance explained Total common variance explained

Factor 1 Prosocial Problems

Factor 2 Externalization Problems

Factor 3 Internalization Problems

—

0.47 — 0.37 — 20.5% 54.3%

0.33 0.49 0.13 0.41 19.1% 43.8%

— 25.6% 49.7%

Note: Reference axis correlations are the partial correlations between two factors when the third factor is held constant.

still indicating relatively good fit of the factor solution to the data (0.08) (Hu and Bentler, 1999). The GFI was 0.97, which also indicates relatively good fit (Bentler and Bonett, 1980). Nearly identical fit statistics were also obtained from a maximum likelihood CFA using Pearson correlations (RMR = 0.04, GFI = 0.94), suggesting that the structure identified by the EFA is robust regardless of whether the SDQ response options are treated as ordered categories or as a continuous scale. DISCUSSION

Historically, rating scales of children’s behaviors (e.g., the Rutter questionnaires) have produced data on two correlated dimensions: emotional and behavioral problems (Boyle and Jones, 1985). The SDQ was designed, in part, to provide data on concentration, peer relations, and social competence for evaluations that include the standard emotional and behavioral components (Goodman, 1994, 1997). PCAs in Britain, Sweden, and Germany have confirmed that independent scores for each of these five components can be created based on parent reports with this new instrument (Goodman, 2001; Smedje et al., 1999; Woerner et al., 2002). The current PCA, performed on a representative U.S. child and adolescent sample, also revealed five components. However, the items that provide the SDQ measures of conduct problems and peer problems were, in some cases, better suited for measures of the other three components. Specifically, being disobedient, lacking a good friend, and being unpopular were more closely related to prosocial problems than to conduct or peer problems. Being the victim of bullies appeared as an indicator of emotional problems rather 1164

than peer problems, and losing one’s temper was more reflective of hyperactivity than conduct problems. Items on lying and being disobedient, which were intended as measures of conduct problems, also had strong subsidiary relationships with the hyperactivityinattention component. These results suggest that some items may have different meanings for American parents than for British, Swedish, or German parents. American parents may also conceptualize the constructs of conduct problems and peer problems differently than do European parents. For example, where European parents may think of these problems as separate from children’s hyperactivity or emotionality, American parents may see these problems as either symptomatic of or direct consequences of hyperactivity or emotionality. The differences could also be due to question wording differences between the American and British forms of the SDQ. Two of the items that were intended to measure conduct problems (“generally well-behaved and usually does what adults request” and “often loses temper”) had been changed from the British wording (“generally obedient and usually does what adults request” and “often has temper tantrums or hot tempers”). However, no modifications were made to the items intended to measure peer problems. EFAs and CFAs were conducted to further explore the dimensions that underlie American parents’ responses to the SDQ items. These analyses suggest that when parents are reporting on their children’s behaviors using the 25-item SDQ, they are likely to be reporting based on three separate, but correlated, underlying dimensions. One dimension was identified by the five items intended to measure hyperactivityinattention, with the addition of items on lying and losing one’s temper. Another dimension was identified

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by the five items intended to measure emotional problems, with the addition of items on being bullied, preferring to be alone, and getting along better with adults than with other children. In other words, the answers to the majority of the items on conduct problems were more closely associated with the same implicit dimension as the items on hyperactivity, and the answers to the majority of the items on peer problems were more closely associated with the same implicit dimension as the items on emotional problems. These two dimensions seem to be very similar to the behavioral and emotional problem concepts commonly assessed with rating scales of children’s behavior (Boyle and Jones, 1985) and can perhaps be labeled as externalizing problems and internalizing problems. The third dimension was identified by the five items intended to measure prosocial behaviors, with the addition of items on being obedient, having a good friend, and being popular. It is easy to interpret this factor as representing the original prosocial behaviors construct, but it should be recognized that these eight items are all positively worded (in contrast to all but two of the remaining items in the SDQ). Goodman (1994, 2001) noted that a factor consisting of these items could also represent a “positive construal” factor, indicating the general extent to which each parent is willing to attribute positive qualities to the child. Because answers to 8 of the 10 positively worded items were most strongly associated with this factor, the likelihood that this factor represents a methodological artifact is increasingly strong. It should be noted, however, that the removal of these items from the SDQ (e.g., to produce a shorter measure of problem behaviors) could result in decreased acceptability by parents and a decrease in the reporting of problem behaviors (e.g., due to a positivity bias in parents’ reports of their children’s behaviors). Such changes to the SDQ are not recommended.

adolescents in Finland (Koskelainen et al., 2001). When this analysis was restricted to a factor solution in which all eigenvalues were greater than 1, a three-factor solution emerged. As with the current results, one factor was defined primarily by items intended to assess hyperactivity and conduct problems, one factor was defined primarily by items intended to assess emotional and peer problems, and one factor consisted of the items intended to assess prosocial behaviors. The Finnish analyses used the self-reported SDQ and an orthogonal rotation, indicating that this factor structure may be invariant across translations, informants, and rotation strategies. Because of the rotation strategy, however, the Finnish study did not reveal the significant relationships between the factors that were observed in the current analyses. Such relationships can be due in part to the positive construal bias mentioned previously; that is, a parent’s willingness to attribute desirable or undesirable qualities to a child can have similar effects on all three factors. However, the partial correlation between the externalizing problems factor and the internalizing problems factor after the removal of the positive construal factor was still strong (0.41), suggesting that this response bias only minimally explains the relationship between the two problem factors. The correlation observed between the externalizing problems factor and the internalizing problems factor in the current analyses was higher than previously reported correlations between the emotional symptoms scale and both the hyperactivity-inattention and the conduct problems scales (Goodman, 2001; Goodman and Scott, 1999). In fact, it was closer in magnitude to the correlations reported by studies using the longer CBCL (Achenbach, 1991). These two factors, therefore, may provide a better assessment of externalization and internalization than do the component scales.

Externalization and Internalization

Relative to other behavioral screening tools, the SDQ requires less time to complete, may be completed by multiple informants, and discriminates children with behavioral problems and psychopathology from other children. As such, the SDQ is particularly useful for health surveys, epidemiologic investigations, and other mass screening procedures in which clinical interviews are not possible and administration time is limited. The current results, however, suggest that the

The current findings regarding the primacy of externalization and internalization dimensions may not be entirely unexpected. The SDQ was developed primarily from the Rutter questionnaires, and Rutter (1967) reported on an antisocial domain and a neurotic domain in his preliminary analysis. Externalization and internalization dimensions also emerged from a factor analysis of the SDQ based on data from a sample of

Conclusion

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component scales published and validated in Britain may not be entirely appropriate for a sample of American children. Three correlated factors—an externalizing dimension, an internalizing dimension, and a positive construal factor—provided better measures of the underlying structure of parents’ responses to the SDQ.

ternalization, internalization, and positive construal dimensions underlie American parents’ responses to the SDQ. Alternative scoring procedures for American children that better reflect these factors may improve the quality of the SDQ’s component measures. Whether these alternative scoring procedures can also improve upon the SDQ’s ability to screen for psychiatric disorders remains to be seen.

Limitations

This conclusion does not invalidate the use of the SDQ in the United States. Indeed, any debate about the relative validity of the three factors versus the five component scales is largely irrelevant to the debate about the validity of the SDQ itself. The recognized validity of the SDQ is based on its association with the presence or absence of psychiatric disorders (Goodman, 1997, 2001; Goodman et al., 1998). It is this discriminant validity that is paramount. Thus, the unidimensionality observed in the current analyses between, for example, the emotional problems items and the peer problems items would be immaterial if those two component scales have different associations with important psychiatric covariates such as the frequency of major depressive episodes (Cheong and Raudenbush, 2000). Clinical Implications

The current results suggest only that parents in the United States differ from their European counterparts in their construal of the domains that the SDQ was designed to assess. Being mindful of these differences, clinicians and researchers should exercise caution when using the SDQ to assess conduct and peer problems (rather than just the presence of any psychiatric disorder). These components are not reliably measured for American children, and additional research is needed to determine whether the use of these components to identify oppositional defiant disorder or conduct disorder, for example, is still valid. In contrast, the current analyses shed little doubt on the measurement reliability of the hyperactivity, emotional, and prosocial components. Presumably, these components still permit the identification of children with attention-deficit/hyperactivity disorder, anxiety disorders, and depression (Goodman, 2001); this discriminant validity was not addressed by the current analyses. The factor analyses, however, reveal that ex1166

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