birth order and sibling gender ratio of a clinical sample of children and adolescents diagnosed with attention deficit hyperactivity disorder.

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.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.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.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.