Cognitive deficits and ethnicity: a cohort study of early psychosis patients in The Netherlands

Incidence rates of psychotic disorders are higher in immigrant groups compared to native populations. This increased risk
may partly be explained by misdiagnosis. Neurocognitive deficits are a core feature of psychotic disorders, but little is
known about the relationship between migration and cognition in psychotic disorders. We examined whether immigrant patients
have cognitive deficits similar to non-immigrant patients, in order to investigate the plausibility of misdiagnosis as explanation
for increased incidence rates.

Patients who made first contact for non-affective psychotic disorder were assessed in the cognitive domains sustained attention,
immediate recall and delayed recall. Immigrant patients were compared to Dutch patients on cognitive performance.

407 Patients diagnosed with a non-affective psychotic disorder completed cognitive assessment (157 Dutch, 250 immigrants).
Both Dutch and immigrant patients showed large cognitive deficits. Between-subgroup comparisons revealed large cognitive deficits
for immigrants compared to Dutch, especially for immigrants from Morocco, Turkey and other non-Western countries.

These results indicate that immigrant status is associated with poorer cognitive functioning in early psychosis. The findings
argue against diagnostic bias as an explanation for the increased incidence of psychotic disorders in immigrants.