As a putative risk for mental disorders, particularly for schizophrenia, migration has reached an increasing interest. There are some evidences of high incidence rates of psychotic disorders in migrant populations. Most of the studies focus on inpatient, first-admissions samples. The aim of this study is to compare the rates of treatment for mental disorders between native-born and migrant patients in an outpatient setting.

A retrospective analysis of all patients (n= 3619) attended throughout the latest 3 years at an outpatient resource involving and area of 92234 inhabitants was carried out. Demographic variables (age, sex, country of birth) and clinical data (diagnosis at first contact and at follow-up, DSM-IV criteria) were collected. Patients were divided in two groups: natives (n=3486) and immigrants (n=133). Comparisons between both groups for the rates of any mental disorder and for syndromic diagnoses were performed.

Compared to native patients, immigrant patients showed higher rates of psychotic disorders (15.2% vs 4.2%, p<0.001, chi square; OR=3.6, 95% CI=2.1-6). As a striking finding, all of the “not specified” diagnostic categories (psychotic disorder NOS, bipolar disorder NOS, depressive disorder NOS, anxiety disorder NOS) were significantly more prevalent in the migrant group.

Among the patients referred to an outpatient mental health resource, a higher prevalence of psychotic disorders in migrants compared to native patients was found. The higher rates of not specified diagnoses in immigrant patients underlines the hazard of misunderstanding their symptoms and, therefore, to overestimate the prevalence of severe disorders in this group.