Background: Attention-deficit/hyperactivity disorder (ADHD) occurs more frequently than expected in prevalent cohorts with epilepsy. The association has been attributed to the epilepsy or its treatment, although it is impossible to determine in previous studies which condition occurs first.
Objectives: To conduct a population-based case-control study of all newly diagnosed unprovoked seizures among Icelandic children younger than 16 years to address the question of time order.
Design: Children with seizures were matched to the next 2 same-sex births from the population registry. The Diagnostic Interview Schedule for Children was used to make a DSM-IV diagnosis of ADHD in a standardized fashion among cases and controls aged 3 to 16 years.
Results: A history of ADHD was 2.5-fold more common among children with newly diagnosed seizures than among control subjects (95% confidence interval [CI], 1.1-5.5). The association was restricted to ADHD predominantly inattentive type (odds ratio [OR], 3.7; 95% CI, 1.1-12.8), not ADHD predominantly hyperactive-impulsive type (OR, 1.8; 95% CI, 0.6-5.7) or ADHD combined type (OR, 2.5; 95% CI, 0.3-18.3). Seizure type, etiology, sex, or seizure frequency at diagnosis (1 or >1) did not affect findings.
Conclusion: Attention-deficit/hyperactivity disorder occurs more often than expected before unprovoked seizures, suggesting a common antecedent for both conditions.