Environmental and Hereditary Factors in the Schizophrenias of Old Age (“Late Paraphrenia”) and their Bearing on the General Problem of Causation in Schizophrenia

The paraphrenias raise a number of problems common to many other disorders in the field of psychiatry, and their solution might therefore advance knowledge in a number of directions. The relationship between paraphrenic, paranoid and schizophrenic illness has long been disputed, and no view at present commands general acceptance. It has seemed to us that these controversies have often turned upon unacknowledged assumptions as to whether clinical, prognostic or genetic criteria, or all of these, were to be employed to decide the issue.