title: Correlation between epilepsy and attention deficit hyperactivity disorder: a population-based cohort study.
abstract: BACKGROUND
  This study presents an evaluation of the bidirectional correlation between attention deficit hyperactivity disorder (ADHD) and epilepsy using 2 cohorts from the same population database.
  
  
  METHODS
  We used data from the Taiwan National Health Insurance Research Database to establish 2 separate cohort studies with participants <19 years old. We subdivided Cohort 1 in 2 groups: (1) 2468 patients initially diagnosed with epilepsy during the period 1999-2008, and (2) 9810 randomly selected sex- and age-matched non-epileptic controls. We subdivided Cohort 2 into 2 groups: (1) 3664 patients with newly diagnosed ADHD and (2) 14 522 sex- and age-matched non-ADHD patients. We evaluated the risk of subsequent ADHD in relationship to epilepsy and vice versa in the 2 cohorts at the end of 2008.
  
  
  RESULTS
  The ADHD incidence in Cohort 1 was 7.76 in patients with epilepsy and 3.22 in those without epilepsy (per 1000 person-years) after a median follow-up of 7-7.5 years. The adjusted hazard ratio (HR) for ADHD was 2.54 (95% CI 2.02-3.18) in the epilepsy group compared to the non-epilepsy group. In Cohort 2, the incidence of epilepsy was 3.24 in patients with ADHD and 0.78 in those without ADHD (per 1000 person-years) after a median follow-up of 3-3.5 years and an HR of 3.94 (95% CI 2.58-6.03).
  
  
  CONCLUSIONS
  This study shows a bidirectional association between ADHD and epilepsy in the 2 cohort studies. Causative factors may be common between these 2 disorders, leading to a cascade of transcriptional changes in the brain that alter behavior or cognition prior to seizures.
authors.affiliation: Children's Medical Center, China Medical University Hospital, Taichung, Taiwan.
authors.forename: I-Ching
authors.initials: IC
authors.lastname: Chou
authors.forename: Yu-Tzu
authors.initials: YT
authors.lastname: Chang
authors.forename: Zheng-Nan
authors.initials: ZN
authors.lastname: Chin
authors.forename: Chih-Hsin
authors.initials: CH
authors.lastname: Muo
authors.forename: Fung-Chang
authors.initials: FC
authors.lastname: Sung
authors.forename: Huang-Tsung
authors.initials: HT
authors.lastname: Kuo
authors.forename: Chang-Hai
authors.initials: CH
authors.lastname: Tsai
authors.forename: Chia-Hung
authors.initials: CH
authors.lastname: Kao
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications* / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003710:Demography; D004827:Epilepsy / Q000150:complications* / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D016016:Proportional Hazards Models; D012307:Risk Factors; D013624:Taiwan / Q000453:epidemiology