There are some proxy risk factors, such as season- and place-of-birth, and migration, which are associated with schizophrenia. These proxies precede but are not directly causally related to the outcome of schizophrenia. They are ecological level variables which are though to reflect another more directly causal factor (or factors) which is, given current knowledge unknown or suspected - but whose evidence is inconclusive.

We now go on to examine some risk factors and indicators.