Environmental influences in schizophrenia: the known and the unknown

Abstract

Despite much research, environmental influences that can be said to cause a schizophrenic illness remain elusive. When the effects of an (often prolonged) prodromal syndrome are taken into account, the first episode appears to come from nowhere. However, over the past couple of decades a number of factors have emerged that can be argued to influence, and not merely reflect, the illness onset. The possible effects of season and geography of birth, urbanisation, immigration, substance misuse, prenatal influenza, famine and other stresses, and obstetric complications are summarised. These varied findings, often of small effect and borderline significance, present a challenge to clinicians attempting to make sense of their patients' life experiences. Any hard conclusions still depend largely on how one formulates the illness.