Psychiatric Emergency Service Use Trends: Adults Experiencing Homelessness in Massachusetts from 2005-2020.

Adults experiencing homelessness (AEH) have high rates of psychiatric conditions, face barriers to accessing psychiatric care, and are high emergency department (ED) utilizers, a setting often unable to address their complex health needs. This study assesses time trends and high frequency utilization by AEH in one psychiatric emergency services (PES) program. A retrospective review of electronic health records from 2005 to 2020 was conducted at an urban PES program serving uninsured and publicly insured adults. Of the 227,553 PES encounters examined, 75,127 (33%) involved AEH. The percentage of PES encounters involving AEH almost doubled from 23.3% in 2005 to 41.6% in 2020. The proportion of AEH using PES aged 55 and older more than tripled, from 4.2% to 15.4%. Adults experiencing homelessness had over six times the odds of being high frequency PES utilizers (10+ visits/year) as housed adults. These findings support interventions addressing housing access within PES encounters.