title: Autistic traits in children with ADHD index clinical and cognitive problems.
abstract: Traits of autistic spectrum disorders (ASD) occur frequently in attention deficit hyperactivity disorder (ADHD), but the significance of their presence in terms of phenotype and underlying neurobiology is not properly understood. This analysis aimed to determine whether higher levels of autistic traits, as measured by the Social Communication Questionnaire (SCQ), index a more severe presentation in a large, rigorously phenotyped sample of children with ADHD (N=711). Regression analyses were used to examine association of SCQ scores with core ADHD features, clinical comorbidities and cognitive and developmental features, with adjustment for putative confounders. For outcomes showing association with total SCQ score, secondary analyses determined levels of differential association of the three ASD sub-domains. Results suggest that increasing ASD symptomatology within ADHD is associated with a more severe phenotype in terms of oppositional, conduct and anxiety symptoms, lower full-scale IQ, working memory deficits and general motor problems. These associations persisted after accounting for ADHD severity, suggesting that autistic symptomatology independently indexes the severity of comorbid impairments in the context of ADHD. Sub-domain scores did not show unique contributions to most outcomes, except that social deficits were independently associated with oppositional symptoms and repetitive behaviours independently predicted hyperactive-impulsive symptoms and motor problems. It would be worthwhile for clinicians to consider levels of socio-communicative and repetitive traits in those with ADHD who do not meet diagnostic criteria for ASD, as they index higher levels of phenotypic complexity, which may have implications for efficacy of interventions.
authors.affiliation: Child and Adolescent Psychiatry Section, Institute of Psychological Medicine and Clinical Neurosciences, MRC Centre for Neuropsychiatric Genetics and Genomics, Cardiff University School of Medicine, Heath Park, Cardiff, CF14 4XN, UK, cooperml1@cardiff.ac.uk.
authors.forename: Miriam
authors.initials: M
authors.lastname: Cooper
authors.forename: Joanna
authors.initials: J
authors.lastname: Martin
authors.forename: Kate
authors.initials: K
authors.lastname: Langley
authors.forename: Marian
authors.initials: M
authors.lastname: Hamshere
authors.forename: Anita
authors.initials: A
authors.lastname: Thapar
mesh_terms: D000223:Adaptation, Psychological; D000293:Adolescent; D001007:Anxiety / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics; D001321:Autistic Disorder / Q000175:diagnosis* / Q000453:epidemiology / Q000235:genetics; D002648:Child; D003072:Cognition Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology; D015897:Comorbidity; D003863:Depression / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D010552:Personality Assessment; D010641:Phenotype; D011594:Psychometrics; D012044:Regression Analysis; D012720:Severity of Illness Index; D012917:Social Adjustment; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires