The effect of socio-demographic factors on mental health and addiction high-cost use: a retrospective, population-based study in Saskatchewan.

OBJECTIVE: A small proportion of the population accounts for the majority of healthcare costs. Mental health and addiction (MHA) patients are consistently high-cost. We aimed to delineate factors amenable to public health action that may reduce high-cost use among a cohort of MHA clients in Saskatoon, Saskatchewan. METHODS: We conducted a population-based retrospective cohort study. Administrative health data from fiscal years (FY) 2009-2015, linked at the individual level, were analyzed (n = 129,932). The outcome of interest was ≥ 90th percentile of costs for each year under study ('persistent high-cost use'). Descriptive analyses were followed by logistic regression modelling; the latter excluded long-term care residents. RESULTS: The average healthcare cost among study cohort members in FY 2009 was ~ $2300; for high-cost users it was ~ $19,000. Individuals with unstable housing and hospitalization(s) had increased risk of persistent high-cost use; both of these effects were more pronounced as comorbidities increased. Patients with schizophrenia, particularly those under 50 years old, had increased probability of persistent high-cost use. The probability of persistent high-cost use decreased with good connection to a primary care provider; this effect was more pronounced as the number of mental health conditions increased. CONCLUSION: Despite constituting only 5% of the study cohort, persistent high-cost MHA clients (n = 6455) accounted for ~ 35% of total costs. Efforts to reduce high-cost use should focus on reduction of multimorbidity, connection to a primary care provider (particularly for those with more than one MHA), young patients with schizophrenia, and adequately addressing housing stability.