Early detection of psychosis is paramount for reducing the duration of untreated psychosis (DUP). One key factor contributing to extended DUP is service delay – the time from initial contact with psychiatric services to diagnosis. Reducing service delay depends on prompt identification of psychosis. Patients with schizophrenia and severe social impairment have been found to have prolonged DUP. Whether service delay significantly contributes to prolonged DUP in this group is unclear.

To examine and compare the course of illness for patients with schizophrenia who are homeless or domiciled, with a focus on service delay in detecting psychosis.

In this case–control study, we included out-patients with a schizophrenia spectrum diagnosis and who were homeless or domiciled but in need of an outreach team to secure continuous treatment. Interviews included psychosocial history and psychopathological and social functioning scales.

We included 85 patients with schizophrenia spectrum disorder. Mean service delay was significantly longer in the homeless group (5.5 years) compared with the domiciled group (2.5 years, P = 0.001), with a total sample mean of 3.9 years. Similarly, DUP was significantly longer in the homeless group, mean 15.5 years, versus 5.0 years in the domiciled group (P < 0.001). Furthermore, the homeless group had an earlier onset of illness than the domiciled group but were almost the same age at diagnosis.

Our findings point to the concerning circumstance that individuals with considerable risk of developing severe schizophrenia experience a substantial delay in diagnosis and do not receive timely treatment.