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We write to respond to an erudite letter to the editor by Zachary J. Williams.1 that extended analyses presented in our recent publication2 investigating the latent structure of autism phenotypic symptoms. The letter by Williams reported results of a bifactor analysis using the standardized loadings and interfactor correlations derived from a Schmid-Leiman orthogonalization of the optimal correlated factor model that we identified. Williams examined the relative contributions of the general and three specific autism symptom factors (ie, social interaction [SI], communication [COM], and restrictive and repetitive behavior [RRB]) to the autism symptom indicators. Those analyses indicated that the majority of autism spectrum disorder (ASD) symptom covariation could be explained by a single general autism factor, whereas the three specific autism symptom factors accounted for minimal covariation among indicators. To pursue the intriguing points raised in the letter, we performed additional analyses using the original raw data.

Objective The two primary—seemingly contradictory—strategies for classifying child psychiatric syndromes are categorical and dimensional; conceptual ambiguities appear to be greatest for polythetic syndromes such as autism spectrum disorder (ASD). Recently, a compelling alternative has emerged that integrates both categorical and dimensional approaches (ie, a hybrid model), thanks to the increasing sophistication of analytic procedures. This study aimed to quantify the optimal phenotypic structure of ASD by comprehensively comparing categorical, dimensional, and hybrid models. Method The sample comprised 3,825 youth, who were consecutive referrals to a university developmental disabilities or child psychiatric outpatient clinic. Caregivers completed the Child and Adolescent Symptom Inventory−4R (CASI-4R), which includes an ASD symptom rating scale. A series of latent class analyses, exploratory and confirmatory factor analyses, and factor mixture analyses was conducted. Replication analyses were conducted in an independent sample (N = 2,503) of children referred for outpatient evaluation. Results Based on comparison of 44 different models, results indicated that the ASD symptom phenotype is best conceptualized as multidimensional versus a categorical or categorical−dimensional hybrid construct. ASD symptoms were best characterized as falling along three dimensions (ie, social interaction, communication, and repetitive behavior) on the CASI-4R. Conclusion Findings reveal an optimal structure with which to characterize the ASD phenotype using a single, parent-report measure, supporting the presence of multiple correlated symptom dimensions that traverse formal diagnostic boundaries and quantify the heterogeneity of ASD. These findings inform understanding of how neurodevelopmental disorders can extend beyond discrete categories of development and represent continuously distributed traits across the range of human behaviors.

Objective This study compared the differential severity of specific symptoms of schizophrenia spectrum disorder (SSD) in children with autism spectrum disorder (ASD) and child psychiatry outpatient referrals (controls). Each group was further subdivided into subgroups with and without co-occurring attention-deficit/hyperactivity disorder (ADHD). Method Children with ASD (n = 147) and controls (n = 335) were evaluated with parent and teacher versions of a psychometrically established DSM-IV -referenced rating scale. Results The two ASD groups (with and without ADHD) had a larger number of more severe SSD symptoms than their respective control groups (with and without ADHD), extending the observation of an association between ASD and SSD to subgroups with and without co-occurring ADHD. The ASD groups exhibited more severe schizoid personality symptoms than controls, but findings for schizophrenia symptoms were mixed. The ASD + ADHD group generally had more severe disorganized thought, disorganized behavior, and negative schizophrenia symptoms than controls (with and without ADHD); nevertheless, findings varied according to ADHD status (present versus absent), individual symptom (symptom specificity), and informant (informant specificity). Ratings of hallucinations and delusions indicated mild severity and few group differences. Negative symptoms such as inappropriate emotional reactions evidenced considerable group divergence. Conclusion Findings provide additional support for an interrelation between ASD and SSD symptoms and the differential influence of neurobehavioral syndromes on co-occurring symptom severity, underscore the multidimensionality of SSD in children with ASD, and suggest how symptom phenotypes may contribute to a better understanding of the etiology, nosology, and possibly clinical management.

Objective To examine differences in risk factors and comorbid conditions for oppositional defiant disorder (ODD) symptom groups in a sample of 248 elementary schoolboys (ages 6-10) recruited from 1994 to 1996. Method The boys and their mothers received multiple assessments of cognitive, behavioral, academic, and family functioning, including a clinic-based evaluation in Stony Brook, NY. ODD was defined using four different strategies for aggregating data from mother and teacher reports of DSM-IV symptoms. Results Source-specific ODD symptom groups had better internal validity and were more differentiated than groups defined using the other strategies. The mother-defined ODD symptom group (ODD/M) had higher levels of maternal detachment than the teacher-defined symptom group (ODD/T), and the ODD/T group had more social problems than the ODD/M group. The classification agreement group (ODD/M + T) evidenced higher levels of sensation-seeking, maternal control, and comorbid symptoms than the ODD/M and ODD/T groups. Controlling for co-occurring attention-deficit/hyperactivity disorder and conduct disorder symptoms altered some of the relationships among ODD, comorbid symptoms, and psychosocial correlates. Conclusions Patterns of co-occurring psychiatric symptoms and psychosocial correlates of ODD symptom groups varied depending on the rater(s) used to determine group membership. Results support continued research into source specificity for conceptualizing ODD.

Objective Two studies were conducted to examine the psychometric properties of a DSM-IV —referenced teacher-completed rating scale in children receiving special education. Method To assess reliability, teachers rated 74 students on two separate occasions (test-retest) using the teacher version of the Child Symptom Inventory-4 (CSI-4T), and teacher aides also rated the children on the first occasion (interrater). In a second study, teacher CSI-4T and Teacher's Report Form (TRF) ratings and consultant diagnoses were obtained for 101 students. Results Internal consistency reliabilities (0.72–0.94), 2-week test-retest reliabilities ( r = 0.61–0.88), and interrater agreement ( r = 0.19–0.56) for the CSI-4T major symptom categories were comparable with dimensional rating scales. CSI-4T ratings showed a consistent pattern of convergent and divergent validity with TRF scores and with consultant diagnoses. Conclusion Findings provide preliminary support for the reliability and validity of the CSI-4T as a measure of DSM-IV symptoms in children receiving special education.

To examine the prevalence of DSM-IV symptoms of attention-deficit/hyperactivity disorder (ADHD), oppositional defiant disorder, and conduct disorder and age, gender, and comorbidity differences between ADHD subtypes.Teachers completed a DSM-IV-referenced symptom inventory for 3,006 schoolchildren aged between 3 and 18 years.The screening prevalence rate of ADHD behaviors was 15.8%; rates for individual subtypes were 9.9% for inattentive, 2.4% for hyperactive-impulsive, and 3.6% for combined. The inattentive type was relatively uncommon in preschool children (3.9%), whereas the hyperactive-impulsive type was least common in teenagers (0.8%). Screening prevalence rates were higher for African-American (39.5%) than white (14.2%) students, but did not vary significantly (p.05) as a function of geographic region or socioeconomic status. ADHD subtypes were rated as more impaired than the non-ADHD group on most measures and were easily differentiated on the basis of comorbid symptoms, social skills impairment, and special education services.The findings of this and similar studies show relatively high convergence for the prevalence of ADHD behaviors and differences between ADHD subtypes.

This study used a parent-completed, DSM-IV-referenced rating scale to examine prevalence rates of attention-deficit/hyperactivity disorder (ADHD) behaviors and differences between subtypes in 10- to 12-year-old Ukrainian children.During 1997, a total of 600 parents and children residing in Kyiv, Ukraine, and their teachers participated in extensive clinical assessments using standard Western measures.The screening prevalence rate of ADHD behaviors was 19.8%: 7.2% for inattentive (I), 8.5% for hyperactive-impulsive (HI), and 4.2% for combined (C). Post hoc comparisons indicated a number of significant (p.05) group differences. Mothers of children with ADHD symptoms reported higher rates of disruptive behavior, negative mother-child interactions, and physical punishment than the non-ADHD group. Teachers rated children with ADHD as more hyperactive and inattentive, but only the HI subtype was rated more oppositional than non-ADHD students. The I subtype was less academically proficient and socially adept (but less likely to have behavior problems). The C subtype was the most behaviorally disruptive (mother ratings), and their fathers were more likely to be aggressive and abuse alcohol. The HI subtype also had problems with disruptive behavior but were less socially impaired.Although symptom prevalence rates are higher in Ukraine than the United States, this study provides additional evidence supporting DSM-IV ADHD subtypes as distinct clinical entities.

Objective To examine the relation between severity of tic disorder and comorbid psychopathology in 47 prepubertal children with tic disorder who were referred for clinical evaluation of and treatment for attention-deficit hyperactivity disorder (ADHD), oppositional behaviors, and aggressive behaviors. Method Parents and teachers completed the Child Behavior Checklist (CBCL) and Teacher's Report Form (TRF) for each child. Results Seventy-five percent of the sample was in the clinical range in at least two categories of psychopathology. When the children were divided into two groups on the basis of tic severity, significantly higher scores were obtained for children with more severe tics on the narrow-band Depressed, Uncommunicative, Obsessive-Compulsive, and Aggressive scales, and the broad-band Internalizing scale of the CBCL. The severity groups did not differ on TRF scores. Children who were more aggressive also received higher CBCL scores. Conclusions The findings from this study suggest that the severity of chronic tics is a clinical indicator of complex psychopathology in children with ADHD who are referred for psychiatric evaluation.

One of the least documented "known" effects of methylphenidate in hyperactive children is the suppression of peer aggression. In this study, 11 aggressive-hyperactive children received a low (0.3 mg/kg) and moderate (0.6 mg/kg) dose of methylphenidate and placebo for 2 weeks each under double-blind conditions. Children were observed in public school settings during classroom seatwork activities, lunch, and recess. Results showed that methylphenidate suppressed nonphysical aggression (p = 0.06) in the classroom, and a moderate dose decreased physical aggression (p less than 0.01) and verbal aggression (p = 0.07) on the playground. The effect on the rate of appropriate social interaction was variable. The majority of subjects exhibited either the same or higher levels of appropriate social interaction on the 0.6 mg/kg dose compared with placebo. In the classroom, both doses of methylphenidate also resulted in reduced levels of motor movement, off-task behavior, noncompliance, and disruptiveness. Teacher ratings of hyperactivity and conduct problem symptoms revealed drug effects, whereas parallel parent instruments did not.