A sex difference in the age of onset of schizophrenia was
noted by Kraepelin (1919). Subsequently epidemiological studies
of the disorder have consistently shown an earlier onset in men
than in women. One model that has been suggested to explain this
observed difference is know as the subtype model
which postulates two type of schizophrenia, one characterised by early
onset, typical symptoms and poor premorbid competence, and the
other by late onset, atypical symptoms, and good premorbid competence.
The early onset type is assumed to be largely a disorder of men
and the late onset largely a disorder of women.