title: Birth order and sibling gender ratio of a clinical sample of children and adolescents diagnosed with attention deficit hyperactivity disorder.
abstract: OBJECTIVE
  It is not clear whether sibling's gender ratio is associated with attention deficit hyperactivity disorder (ADHD). This study examines whether inattentiveness severity and hyperactivity/impulsivity severity are associated with birth order of children with ADHD.
  
  
  METHODS
  Participants are a clinical sample of 173 children and adolescents with ADHD and 43 ones without ADHD. Diagnoses were made using Diagnostic and Statistical Manual of Mental Disorders forth edition-Text Revision (DSM-IV-TR), diagnostic criteria according to face-to-face interview with the children and their parents. ADHD DSM-IV checklist was used to measure inattentiveness and hyperactivity/impulsivity scores.
  
  
  RESULTS
  The association of birth order and diagnosis of ADHD was not statistically significant after adjusting for covariate factors. The gender ratio of siblings is not associated with ADHD.
  
  
  CONCLUSIONS
  Birth order and siblings gender ratio are independent of ADHD diagnosis. The results of this study support the fact that genetic factors rather than environmental factor of birth order is associated with ADHD. Moreover, contrary to autism, the current results do not suggest the androgen theory for ADHD.
authors.affiliation: Research Center for Psychiatry and Behavioral Sciences, 2Department of Psychiatry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Ghanizadeh
authors.forename: Marzie
authors.initials: M
authors.lastname: Abotorabi-Zarchi
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Mohammadi
authors.forename: Ali
authors.initials: A
authors.lastname: Firoozabadi
keywords: Attention deficit disorder with hyperactivity; Birth order; Sex ratio