ABSTRACT
The scientific literature on causal and risk factors in schizophrenia is now so immense that even a summary based only on studies whose design and methods are adequate by the standards of their time would run into volumes. Problems in comparing incidence rates arising from variations between the denominators are most clearly demonstrated in studies involving countries whose population statistics are of doubtful reliability, and where estimates of the population size and indices such as birth and death rates may be seriously inaccurate. The risk factor most securely associated with schizophrenia is genetic. The disorder, whether broadly or narrowly defined, occurs more commonly among the first degree relatives of those afflicted than in control groups or the general population. Genetic studies of schizophrenia have not been carried out as thoroughly, or to the same extent, in Third World compared with developed countries.
