Crossing the divide: Use of health services during the handover period from child and adolescent to adult mental health services, 2008-2021. A Norwegian National register study.

Background Adolescence and early adulthood represent periods of heightened vulnerability to mental health disorders. In Norway, mental health care shifts from child and adolescent mental health services to adult mental health services at age 18, which may result in fragmented transitions and treatment discontinuity. The aim of this study was to examine health service use and patterns between ages 15 and 21, with particular attention to the transition in specialist mental health services that typically occur around age 18. Methods We conducted a population-wide registry study including all Norwegians aged 15–21 between 2008 and 2021 (n = 1,313,077). Health service utilization was analyzed using Poisson regression. Subgroup analyses included individuals with established mental health needs, namely all adolescents with a GP-recorded mental health diagnosis (n = 372,109) and those with child and adolescent mental health service contact at age 17 (n = 71, 779). Results Specialist mental health service use peaked at age 16, declined sharply after 18, and reached its lowest levels around 20. In contrast, GP and out-of-hours GP consultations increased steadily, particularly after age 18, while somatic and acute somatic services remained stable. The same pattern appeared in both subgroup analyses, of youth with a GP-recorded mental health diagnosis and in those with recent contact with child and adolescent mental health services at age 17. Conclusion Specialist mental health service use declines sharply after the transition to adult care, while GP reliance increases. These findings suggest structural rather than clinical causes, highlighting the need for better continuity across the change in mental health service levels.