Physical disease and schizophrenia.

Researchers have long speculated about the existence of a relationship between physical disease and schizophrenia. Psychodynamic and life-stress theories offer opposing predictions about the nature of this relationship. Unfortunately, the empirical research on this topic is often contradictory and frequently plagued by various methodological inadequacies. Despite the theoretical controversy and methodological problems, the present review of the empirical literature suggests that patients with schizophrenia may be at increased risk for breast cancer and possibly for cardiovascular disease. On the other hand, patients with schizophrenia seem to be at reduced risk for developing either rheumatoid arthritis or lung cancer. The epidemiological investigations are worth pursuing since the convincing demonstration of a relationship between schizophrenia and a particular physical disease would yield valuable information about the pathogenesis of both disorders. Future research on this topic will need to consider the possible mediating effects of third variables, such as smoking habits, which may be associated with schizophrenia and which also are, independently, recognized as risk factors for particular physical disorders.