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

Background During recent years the strategy for aetiological research in sc hizophrenia has been to concentrate on two closely connected directions: th e 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 conduc ted 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 identif ying high-risk individuals at an early stage of life and perhaps establishi ng specific preventive programmes. There is, however, a great need for clos er international collaboration in future research. Declaration of interest None.