The association between exposure to perinatal risk factors and increased vulnerability for schizophrenia is now documented by a large body of epidemiologic studies. However, the diagnostic specificity of this association may be questioned, because subjects with a history of exposure to early environmental risk factors are at an increased risk for other psychiatric disorders with childhood or adult onset, such as autism, anorexia nervosa, or affective disorders. Because a given risk factor may be associated with several adverse health outcomes, these findings do not preclude the existence of a causal relationship between perinatal risk factors and schizophrenia. This lack of diagnostic specificity suggests that the clinical expression of the vulnerability induced by early risk factors depends on gene-environment interactions or interaction between this prenatally determined vulnerability and exposure to later environmental risk factors.