Birth Order and Schizophrenia

Abstract
Characteristics which are wholly genetically determined are distributed at random among all the members of a sibship. Dependence of the distribution on birth rank (i.e. maternal parity at the birth of the subjects) or on position within the sibship provides presumptive evidence of non-genetic causes and may give some indication of their nature (McKeown and Record, 1956). Investigations on the birth order of schizophrenics (Tables VI and VII) have to date given no clear and consistent results, and further study appears to be indicated.