Family history of psychiatric disorders and age at first contact in schizophrenia: An epidemiological study

BACKGROUND: The risk for schizophrenia has been associated with a family history of this and other psychiatric disorders. The relationship between age at first contact and family history of psychiatric illness is not certain. AIMS: To estimate the risks for schizophrenia associated with a range of psychiatric diagnoses in family members and to investigate the relationship between these risks and age at first contact for schizophrenia. METHOD: A nested case-control study design was employed. Psychiatric admission data and socio-economic data were available for 7704 cases admitted between 1981 and 1998 in Denmark, 192,590 gender- and age-matched controls, and for the parents and siblings of all subjects. RESULTS: Controlling for socio-economic factors, risk for schizophrenia was associated with a family history of all psychiatric disorders except substance misuse and independently with a family history of suicide. The risk for schizophrenia associated with a family history of psychiatric disorders decreased as age at first contact increased. CONCLUSIONS: Risk for schizophrenia is associated with a range of psychiatric disorders in family members and these risks are not constant across the risk period.