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Risk for schizophrenia and schizophrenia-like psychosis among patients with epilepsy: population based cohort study

BMJ 2005; 331 doi: (Published 30 June 2005) Cite this as: BMJ 2005;331:23
  1. Ping Qin (pq{at}, associate professor1,
  2. Huilan Xu, associate professor2,
  3. Thomas Munk Laursen, statistician1,
  4. Mogens Vestergaard, assistant professor3,
  5. Preben Bo Mortensen, professor1
  1. 1 National Centre for Register-based Research, University of Aarhus, Taasingegade 1, DK-8000, Aarhus C, Denmark
  2. 2 Department of Social Medicine and Health Management, School of Public Health, Central South University, China
  3. 3 Department of Epidemiology, Institute of Public Health, University of Aarhus, Denmark
  1. Correspondence to: P Qin
  • Accepted 29 April 2005


Objectives To investigate whether age at onset of epilepsy, type of epilepsy, family history of psychosis, or family history of epilepsy affect the risk of schizophrenia or schizophrenia-like psychosis among patients with epilepsy.

Design Comparison of population based data.

Setting Danish longitudinal registers.

Subjects The cohort comprised 2.27 million people.

Main outcome measures Epilepsy, psychosis, personal birth data.

Results We found an increased risk of schizophrenia (relative risk 2.48, 95% confidence interval 2.20 to 2.80) and schizophrenia-like psychosis (2.93, 2.69 to 3.20) in people with a history of epilepsy. The effect of epilepsy was the same in men and in women and increased with age. Family history of psychosis and a family history of epilepsy were significant risk factors for schizophrenia and schizophrenia-like psychosis, and the effect of epilepsy, both in cases and families, was greater among people with no family history of psychosis. In addition, the increased risk for schizophrenia or schizophrenia-like psychosis did not differ by type of epilepsy but increased with increasing number of admissions to hospital and, particularly, was significantly greater for people first admitted for epilepsy at later ages.

Conclusions There is a strong association between epilepsy and schizophrenia or schizophrenia-like psychosis. The two conditions may share common genetic or environmental causes.


  • Contributors All authors participated in discussions about study design, analysis, and interpretation of the data and contributed to revision of the manuscript. PQ, HX, and TML analysed the data. HX prepared the first draft of manuscript. PQ wrote the report, finalised the manuscript, and is guarantor.

  • Funding Stanley Medical Research Institute, USA, and the Danish Medical Research Council (grant No 22-02-0207). The National Centre for Register-based Research is supported by Danish National Research Foundation, Denmark.

  • Competing interests None declared.

  • Ethical approval Danish Data Protection Agency.

  • Accepted 29 April 2005
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