In order to investigate the validity of Foulds' hierarchical model of psychiatric illness a cross-cultural study was carried out. The DSSI, a self-report symptom inventory, was administered to 100 English psychiatric patients and a translated version was administered to 100 Turkish psychiatric patients. The report of symptoms in both nationality groups conformed to Foulds' hierarchy principles in 93 per cent and 87 per cent of cases respectively.
When the reporting of symptoms within classes was investigated, nationality effects were observed to influence the self-reporting of ‘hysterical’ neurotic symptoms, irrespective of diagnostic class. Nationality was also observed to influence the reporting of ‘delusional’ symptoms, but in non-psychotic patients.
These results suggest that Foulds' model is a useful one in cross-cultural psychiatry, because it indicates both the universal features of hierarchical ordering of symptoms and the cultural influence on those symptoms which do not define the diagnostic class of the patient.