Toxic exposures and psychiatric disease--lessons from the epidemiology of cancer.

Toxic chemicals such as lead, methyl mercury, organic solvents, manganese, kepone, and the organophosphates are recognized to cause psychiatric disease. Whether such associations are exceptional, or if in fact a high proportion of all psychiatric illnesses are of toxic environmental etiology, and therefore potentially avoidable, is not known. Epidemiologic studies of cancer, particularly analyses of geographic variations in mortality, of variations in incidence in migrant populations, of trends over time, and of induction by environmental agents suggest that extragenetic environmental factors (tobacco, alcohol, drugs, diet, radiation, air pollution, and industrial chemicals) may account for the majority of all human cancers. Similar application of epidemiologic techniques to the study of psychiatric illnesses might yield etiologic clues in relation to toxic environmental exposures and may also suggest approaches to disease prevention.