title: Phenotype refinement for comorbid attention deficit hyperactivity disorder and reading disability.
abstract: Comorbidity between Attention Deficit Hyperactivity Disorder (ADHD) and reading disability (RD) is common; however, the heritability of this comorbidity is not well understood. This may be due to the complexity and heterogeneity of ADHD and RD phenotypes. Using alternative ADHD-RD sub-phenotypes instead of those arising from the DSM-IV may lead to greater success in the search for comorbid ADHD-RD susceptibility genes. Therefore, this study aims to refine ADHD-RD phenotypes into homogenous informative sub-phenotypes using latent class analysis (LCA). LCA was performed on 2,610 Australian twin families (6,535 individuals) in order to generate probabilistic genetically distinct classes that define ADHD-RD subtypes, including comorbidity, based on related symptom clusters. The LCA separated the phenotypes for ADHD and RD into nine classes. One class was unaffected; three classes demonstrated the three DSM-IV subtypes of ADHD, three subtypes showed different severities of RD, and two classes expressed a combination of RD and ADHD subtypes. LCA proved effective in refining the phenotypes of ADHD alone, RD alone, and ADHD-RD comorbidity, and its ability to classify them into homogenous groups based on clusters of symptoms, suggesting that the latent classes may be robust enough to use in molecular genetic studies.
authors.affiliation: School of Psychology & Speech Pathology, Curtin Health Innovation Research Institute, Curtin University, Western Australia, Australia.
authors.forename: Abdullah R
authors.initials: AR
authors.lastname: Sheikhi
authors.forename: Neilson
authors.initials: N
authors.lastname: Martin
authors.forename: David
authors.initials: D
authors.lastname: Hay
authors.forename: Jan P
authors.initials: JP
authors.lastname: Piek
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology*; D001315:Australia / Q000453:epidemiology; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D015897:Comorbidity; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004410:Dyslexia / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D010641:Phenotype; D015995:Prevalence; D011932:Reading; D012727:Sex Characteristics; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic