title: Autistic-like traits and their association with mental health problems in two nationwide twin cohorts of children and adults.
abstract: BACKGROUND
  Autistic-like traits (ALTs), that is restrictions in intuitive social interaction, communication and flexibility of interests and behaviors, were studied in two population-based Swedish twin studies, one in children and one in adults: (1) to examine whether the variability in ALTs is a meaningful risk factor for concomitant attention deficit hyperactivity disorder (ADHD), anxiety, conduct problems, depression and substance abuse, and (2) to assess whether common genetic and environmental susceptibilities can help to explain co-existence of ALTs and traits associated with such concomitant problems.
  
  
  METHODS
  Two nationwide twin cohorts from Sweden (consisting of 11 222 children and 18 349 adults) were assessed by DSM-based symptom algorithms for autism. The twins were divided into six groups based on their degree of ALTs and the risk for concomitant mental health problems was calculated for each group. Genetic and environmental susceptibilities common to ALTs and the other problem types were examined using bivariate twin modeling.
  
  
  RESULTS
  In both cohorts, even the lowest degree of ALTs increased the risk for all other types of mental health problems, and these risk estimates increased monotonically with the number of ALTs. For all conditions, common genetic and environmental factors could be discerned. Overall, the phenotypic correlation between ALTs and the traits examined were less pronounced in adulthood than in childhood and less affected by genetic compared with environmental factors.
  
  
  CONCLUSIONS
  Even low-grade ALTs are relevant to clinical psychiatry as they increase the risk for several heterotypical mental health problems. The association is influenced partly by common genetic and environmental susceptibilities. Attention to co-existing ALTs is warranted in research on a wide range of mental disorders.
authors.affiliation: Institute of Clinical Sciences, Lund University, Malmö, Sweden. sebastian.lundstrom@med.lu.se
authors.forename: S
authors.initials: S
authors.lastname: Lundström
authors.forename: Z
authors.initials: Z
authors.lastname: Chang
authors.forename: N
authors.initials: N
authors.lastname: Kerekes
authors.forename: C H
authors.initials: CH
authors.lastname: Gumpert
authors.forename: M
authors.initials: M
authors.lastname: Råstam
authors.forename: C
authors.initials: C
authors.lastname: Gillberg
authors.forename: P
authors.initials: P
authors.lastname: Lichtenstein
authors.forename: H
authors.initials: H
authors.lastname: Anckarsäter
mesh_terms: D000293:Adolescent; D000328:Adult; D001008:Anxiety Disorders / Q000453:epidemiology; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology* / Q000235:genetics*; D015331:Cohort Studies; D015897:Comorbidity; D003866:Depressive Disorder / Q000453:epidemiology; D004200:Diseases in Twins / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology*; D012306:Risk; D019966:Substance-Related Disorders / Q000453:epidemiology; D013548:Sweden / Q000453:epidemiology