title: Evidence for shared susceptibility to epilepsy and psychosis: a population-based family study.
abstract: BACKGROUND
  There is emerging evidence of an etiological overlap between a range of neurodevelopmental disorders, including schizophrenia and epilepsy. Here we investigate shared familial vulnerability to psychotic illness and epilepsy in a family-based study.
  
  
  METHODS
  The study population consisted of parents and their children born in Helsinki between 1947 and 1990. The Finnish Hospital Discharge Register was used to determine psychiatric and neurological outcomes in adulthood for all offspring. Parental history of psychosis and epilepsy was determined by linking the Hospital Discharge Register and the Finnish Population Register.
  
  
  RESULTS
  Our total sample comprised 9653 families and 23,404 offspring. Individuals with epilepsy had a 5.5-fold increase in the risk of having a broadly defined psychotic disorder, an almost 8.5-fold increase in the risk of having schizophrenia, and a 6.3-fold increase in the risk of having bipolar disorder. There was strong evidence of clustering of the association between epilepsy and psychosis within families. Individuals with a parental history of epilepsy had a 2-fold increase in the risk of developing psychosis, compared with individuals without a parental history of epilepsy. Individuals with a parental history of psychosis had, reciprocally, a 2.7-fold increase in the risk of having a diagnosis of generalized epilepsy, compared with individuals without a parental history of psychosis. Post hoc analyses showed that these associations were not driven by the comorbidity of epilepsy and psychosis in the parents.
  
  
  CONCLUSIONS
  These findings support recent evidence of overlapping etiological factors between epilepsy and schizophrenia, especially recent evidence of a genetic overlap between these disorders.
authors.affiliation: Department of Psychiatry, Royal College of Surgeons in Ireland, Dublin, Ireland. maryclarke@rcsi.ie
authors.forename: Mary C
authors.initials: MC
authors.lastname: Clarke
authors.forename: Antti
authors.initials: A
authors.lastname: Tanskanen
authors.forename: Matti O
authors.initials: MO
authors.lastname: Huttunen
authors.forename: Maurice
authors.initials: M
authors.lastname: Clancy
authors.forename: David R
authors.initials: DR
authors.lastname: Cotter
authors.forename: Mary
authors.initials: M
authors.lastname: Cannon
mesh_terms: D001714:Bipolar Disorder / Q000150:complications / Q000453:epidemiology / Q000235:genetics; D004827:Epilepsy / Q000150:complications / Q000453:epidemiology / Q000235:genetics*; D005192:Family Health / Q000706:statistics & numerical data*; D005387:Finland / Q000453:epidemiology; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D044382:Population Groups / Q000235:genetics; D011618:Psychotic Disorders / Q000150:complications / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology; D012307:Risk Factors; D012559:Schizophrenia / Q000150:complications / Q000453:epidemiology / Q000235:genetics