Epidemiology in neurobiological research: Exemplified by the influenza-schizophrenia theory

Abstract

Background: During recent years the strategy for aetiological research in schizophrenia has been to concentrate on two closely connected directions: the search for the genetic element and the search for environmental factors. Damage to the immature brain during pregnancy and delivery has given us the most interesting results from recent environmental research. Aims: To examine the validity of the influenza-schizophrenia hypothesis. Method: A review of register-based epidemiological studies in Denmark conducted over a 10-year period. Results: The studies reviewed provided strong inferential evidence in favour of the hypothesis, but some methodological problems are unresolved and not all replication studies have been positive. Conclusions: The brain-damage hypothesis points to possibilities for identifying high-risk individuals at an early stage of life and perhaps establishing specific preventive programmes. There is, however, a great need for closer international collaboration in future research. Declaration of interest: None.