title: Association between Attention-Deficit Hyperactivity Disorder in childhood and schizophrenia later in adulthood.
abstract: OBJECTIVE
  To estimate the risk of schizophrenia in adulthood among children and adolescents with ADHD compared to the background population.
  Two hundred and eight youths with ADHD (183 boys; 25 girls) were followed prospectively. Diagnoses of schizophrenia were obtained from The Danish Psychiatric Central Register. The relative risk (RR) of schizophrenia for cases with ADHD, compared to the normal population, was calculated as risk ratios. Hazard ratios (HR's) by Cox regression were calculated in the predictor analyses.
  
  
  RESULTS
  Mean age for ADHD cases at follow-up was 31.1years. Schizophrenia diagnoses were given to 3.8% of these cases. Compared to the general population, RR of schizophrenia in cases with ADHD was 4.3 (95% CI 1.9-8.57).
  
  
  CONCLUSIONS
  This prospective follow-up study found children with ADHD to be at higher risk of later schizophrenia than controls. If replicated, these results warrant increased focus on the possible emergence symptoms of schizophrenia or schizophreniform psychosis during clinical follow-up of patients with ADHD.
authors.affiliation: National Centre for Register-based Research, Department of Economics and Business, School of Business and Social Sciences, Aarhus University, Aarhus, Denmark; Center for Child and Adolescent Psychiatry, Aarhus University Hospital, Aarhus, Denmark; Department for Child and Adolescent Psychiatry, Hospital of Telemark, Kragerø, Norway; The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus and Copenhagen, Denmark. Electronic address: sdalsgaard@ncrr.dk.
authors.forename: S
authors.initials: S
authors.lastname: Dalsgaard
authors.affiliation: National Centre for Register-based Research, Department of Economics and Business, School of Business and Social Sciences, Aarhus University, Aarhus, Denmark; The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus and Copenhagen, Denmark.
authors.forename: P B
authors.initials: PB
authors.lastname: Mortensen
authors.affiliation: Section of Biostatistics, Department of Public Health, University of Aarhus, Aarhus, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Frydenberg
authors.affiliation: Psychiatric Center Copenhagen, University of Copenhagen, Copenhagen, Denmark.
authors.forename: C M
authors.initials: CM
authors.lastname: Maibing
authors.affiliation: The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus and Copenhagen, Denmark; Psychiatric Center Copenhagen, University of Copenhagen, Copenhagen, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Nordentoft
authors.affiliation: Center for Child and Adolescent Psychiatry, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: P H
authors.initials: PH
authors.lastname: Thomsen
mesh_terms: D000293:Adolescent; D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012306:Risk; D012559:Schizophrenia / Q000209:etiology*
keywords: Attention-Deficit/Hyperactivity Disorder (ADHD); Methylphenidate; Pharmacoepidemiology; Prevalence; Psychotic disorders; Schizophrenia