To describe rates of service contacts for substance use (SU) and mental ill-health (MiH) among people released from Scottish prisons and to find subgroups with the highest service use within the prison-experienced population, to identify those most in need of post-prison support.

Retrospective cohort study using linked Scottish Prison Service (SPS) data and health data, including scheduled (inpatient and psychiatric hospitalisations, outpatient contacts, community prescribing, Scottish Drug Misuse Database records), and unscheduled and urgent care services (out-of-hours primary care contacts, NHS24 helpline contacts, accident and emergency admissions, ambulance callouts). Data for all individuals released from prison in 2015 were extracted for 4 years pre- and post- their release (index) date.

Data on 8,313 prison-exposed individuals were extracted and linked. In a comparison with a 1:5 matched general population sample (matched on age, sex, deprivation and geographical area), we found that prison exposure was associated with increased service use for all types of service (SU, MiH, or dual-diagnosis, DD), including after adjusting for prior service use, time spent in prison prior to release, post-index time in prison, and comorbidity. Service use in prison-exposed individuals will be analysed stratified by age, sex, comorbidity, deprivation, geographical area, ethnicity, sexual orientation, disability, veteran status, and gender identity, depending on data completeness in SPS records. Poisson regression models with robust standard errors will be used to model associations between service use and individual characteristics.

The results of this novel data linkage provide national-level estimates of service use for MiH and SU, which will serve as crucial evidence in future healthcare delivery for justice-experienced populations. Identifying subgroups with the highest support needs will enable better post-release interventions for SU and MiH.