A century of delusions in south west Scotland.

Two groups of patients admitted to psychiatric hospital in Dumfries were studied, drawn from the periods 1880-1889 and 1970-1979. Feighner criteria were applied to make three diagnostic categories - depression, mania and schizophrenia - and the occurrence and content of delusions were noted for each. A significant decline in the prevalence of delusional depressive illness was found between the two periods, and a similar trend was noted for delusional manic illness. In contrast, the prevalence of delusional schizophrenic illness was stable. This decline is taken to reflect a change in the phenomenology of affective illness since last century in South West Scotland. The content of delusions is also discussed.