Predictive validity of a culturally informed diagnosis of schizophrenia: a 30 month follow-up study with first episode psychosis

Previous research has shown discrepancies between a standard diagnostic interview for schizophrenia (CASH) and a culture sensitive version of this instrument (CASH-CS) in Moroccan patients. More specifically we showed that among Moroccan immigrants the CASH-CS resulted in fewer patients with a diagnosis of schizophrenia compared with diagnoses based on the CASH, whereas for Native Dutch patients there was no difference between the CASH and the CASH-CS. The aim of the current study was to compare the predictive validity of a diagnosis of schizophrenia according to the CASH and CASH-CS. Thirty months after referral, 26 Moroccan and 26 native Dutch patients with a suspected first psychotic episode were compared with regard to 30-month diagnostic stability, symptom development, psychosocial functioning, medication use and hospitalization using baseline diagnoses based on the two versions of the CASH. Moroccan patients who were diagnosed with schizophrenia using the standard CASH at baseline had a significantly better 30-month prognosis than native Dutch patients with the same CASH diagnosis. Prognosis of schizophrenia according to the CASH-CS was similar for Moroccans and native Dutch patients. Diagnostic stability according to the CASH was high for native Dutch (92%), but low for Moroccan patients (27%), whereas diagnostic stability according to the CASH-CS was high for both groups (85% and 81%, respectively). These data raise questions regarding the validity of the standard CASH in Moroccan immigrants in The Netherlands and support the validity of the CASH-CS. As a consequence, there are serious doubts about the validity of previous studies showing an increased incidence of schizophrenia in immigrants using standard diagnostic procedures