title: The Genetic Overlap of Attention-Deficit/Hyperactivity Disorder and Autistic-like Traits: an Investigation of Individual Symptom Scales and Cognitive markers.
abstract: Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASDs) frequently co-occur. However, due to previous exclusionary diagnostic criteria, little is known about the underlying causes of this covariation. Twin studies assessing ADHD symptoms and autistic-like traits (ALTs) suggest substantial genetic overlap, but have largely failed to take into account the genetic heterogeneity of symptom subscales. This study aimed to clarify the phenotypic and genetic relations between ADHD and ASD by distinguishing between symptom subscales that characterise the two disorders. Moreover, we aimed to investigate whether ADHD-related cognitive impairments show a relationship with ALT symptom subscales; and whether potential shared cognitive impairments underlie the genetic risk shared between the ADHD and ALT symptoms. Multivariate structural equation modelling was conducted on a population-based sample of 1312 twins aged 7-10. Social-communication ALTs correlated moderately with both ADHD symptom domains (phenotypic correlations around 0.30) and showed substantial genetic overlap with both inattention and hyperactivity-impulsivity (genetic correlation = 0.52 and 0.44, respectively). In addition to previously reported associations with ADHD traits, reaction time variability (RTV) showed significant phenotypic (0.18) and genetic (0.32) association with social-communication ALTs. RTV captured a significant proportion (24 %) of the genetic influences shared between inattention and social-communication ALTs. Our findings suggest that social-communication ALTs underlie the previously observed phenotypic and genetic covariation between ALTs and ADHD symptoms. RTV is not specific to ADHD symptoms, but is also associated with social-communication ALTs and can, in part, contribute to an explanation of the co-occurrence of ASD and ADHD.
authors.affiliation: King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology, and Neuroscience, De Crespigny Park, SE5 8AF, London, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Pinto
authors.affiliation: King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology, and Neuroscience, De Crespigny Park, SE5 8AF, London, UK.
authors.forename: Fruhling
authors.initials: F
authors.lastname: Rijsdijk
authors.affiliation: Department of Psychological Sciences, Birkbeck, University of London, London, UK.
authors.forename: Angelica
authors.initials: A
authors.lastname: Ronald
authors.affiliation: King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology, and Neuroscience, De Crespigny Park, SE5 8AF, London, UK.
authors.forename: Philip
authors.initials: P
authors.lastname: Asherson
authors.affiliation: King's College London, MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology, and Neuroscience, De Crespigny Park, SE5 8AF, London, UK. jonna.kuntsi@kcl.ac.uk.
authors.forename: Jonna
authors.initials: J
authors.lastname: Kuntsi
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology* / Q000235:genetics*; D000067877:Autism Spectrum Disorder / Q000453:epidemiology* / Q000235:genetics*; D002648:Child; D060825:Cognitive Dysfunction / Q000453:epidemiology* / Q000235:genetics*; D015897:Comorbidity; D004200:Diseases in Twins; D005260:Female; D006801:Humans; D008131:London / Q000453:epidemiology; D008297:Male; D010641:Phenotype
keywords: Attention-deficit/hyperactivity disorder (ADHD); Autism spectrum disorders (ASDs); Autistic-like traits (ALTs); Genetics; Reaction time variability (RTV)