An exploratory study of psychosis risk factors in individuals who are referred but do not meet criteria for an early intervention in psychosis service.

Background: The 'at-risk mental state' (ARMS) for psychosis has been critiqued for its limited prognostic ability and identification of a limited proportion of those who will develop a first episode of psychosis (FEP). Broadening the search for high-risk groups is key to improving population-level ascertainment of psychosis risk.

Aims: To explore risk enrichment in diagnostic, demographic and socio-functional domains among individuals referred to an early intervention in psychosis (EIP) service not meeting ARMS or FEP criteria.

Method: A retrospective file review of 16 years of referrals to a tertiary EIP service in Ireland was undertaken. Diagnostic outcomes from standardised assessments (Structured Clinical Interview for DSM), demographic (age, gender, family history, nationality) and socio-occupational (relationship status, living status, working status) variables were compiled for those not meeting criteria. These were compared with individuals diagnosed with an FEP in the same period.

Results: From 2005 to 2021 inclusive, of 2025 index assessments, 27.6% ( = 558) did not meet either FEP or ARMS criteria, which is notably higher than the 5.4% ( = 110) meeting ARMS criteria. This group had high psychiatric morbidity, with 65.4% meeting criteria for at least one DSM Axis I disorder. Depressive, anxiety and substance use disorders predominated. Their functional markers were poor, and comparable to the FEP cohort.

Conclusions: This group is enriched for psychosis risk factors. They are a larger group than those meeting ARMS criteria, a finding that may reflect EIP service configuration. They may be an important focus for further study in the search for at-risk populations beyond the current ARMS model.