Parental socio-economic status and risk of first admission with schizophrenia - A Danish national register based study

Background We examined the relationships between measures of parental and personal socio-economic status and risk of first admission with schizophrenia in order to identify whether low socio-economic status in cases is a consequence of the illness process or is a familial risk factor. Methods A national population-based nested case-control study based on Danish longitudinal registers was conducted. The sample included 7704 first admissions with ICD-8 or ICD-10 schizophrenia admitted to a psychiatric facility in Denmark between 1981 and 1998 and 192 590 individually time-, age- and gender-matched population controls identified through national registers, and their parents and siblings. Socio-economic indicators measured in the year prior to admission and background factors for cases, controls, and parents were included. Results Risk of schizophrenia was associated with unemployment, low educational attainment, being single, lower wealth status, low income, and being childless. Increased risk was associated with a family history of psychiatric disorders, birth in urban areas, birth outside of Denmark, and having three of more siblings. Increased risk of schizophrenia was associated with parental unemployment and parental lower income, but was not associated with parental wealth. Risk for schizophrenia was associated with higher education in parents. Conclusions Increased risk of first admission was associated with socio-economic disadvantage in cases. Although we found some associations between parental unemployment and parental higher education and risk of schizophrenia, there was little evidence that low parental socio-economic status increases the risk of schizophrenia.