Mental Health Care Use Among Children and Adolescents With High Health Care Costs in Ontario, Canada

IMPORTANCE: Research on patients with high health care costs has examined mainly adults, with little focus on mental health care use. OBJECTIVE: To examine the characteristics and costs of children and adolescents with high health care costs who use mostly mental health care and whether and why they persist in the high-cost state. DESIGN, SETTING, AND PARTICIPANTS: This population-based, retrospective cohort study used health care records from Ontario, Canada, on all children and adolescents (age 0-17 years) covered under a universal health care system from January 1, 2012, to December 31, 2019. All children and adolescents in and above the 90th percentile of the cost distribution in 2012 for whom costs related to mental health care accounted for 50% or more of their costs were defined as patients with high mental health care costs. Data were analyzed from August 2019 to December 2022. EXPOSURES: High health care costs. MAIN OUTCOMES AND MEASURES: Patients with high mental health care costs were characterized in terms of their sociodemographic characteristics; chronic physical health, mental health, and behavioral conditions; and health care costs (in 2021 Canadian dollars) by health service and type of care (mental health care vs non–mental health care). Patients were followed up until 2019 to assess whether they persisted in the high-cost state and to examine factors associated with persisting in that state. RESULTS: In 2012, there were 273 490 children and adolescents with high health care costs (mean [SD] age, 6.43 [5.99] years; 55.8% male; mean cost, $7936.40; 95% CI, $7850.30-$8022.40). Of these, 20 463 (7.5%) were classified as having high mental health care costs (mean cost, $10 040.20; 95% CI, $9822.80-$10 257.50). Asthma (30.3%), attention-deficit/hyperactivity disorder (35.8%), and mood and/or anxiety disorders (94.9%) were the most common chronic physical, behavioral, or mental health conditions. Few patients with high mental health care costs persisted in the high-cost state beyond 3 years (19.0%). Mood and/or anxiety disorders (relative risk ratio [RRR], 6.17; 95% CI, 3.19-11.96) and schizophrenia spectrum disorders (RRR, 2.98; 95% CI, 2.14-4.14) were identified as the main factors associated with persistence in the high-cost state. CONCLUSIONS AND RELEVANCE: In this cohort study of children and adolescents with high health care costs, some patients had high levels of mental health care use and high costs of care, but few of these persisted in the high-cost state for 3 or more years. These findings may help inform the development of care coordination interventions and service delivery models, such as youth integrated services, to reduce costs and improve outcomes for children and adolescents.