Trends and Changing Clinical Profiles in Adolescent Mental Health Inpatient Admissions: A Time-Series and Comparative Study Over the Period 2011–2024

Abstract

Background: This study analysed long-term trends and clinical characteristics of adolescents admitted to an Inpatient Mental Health Unit (IMHU), and examined whether the onset of the coronavirus disease (COVID-19) pandemic modified historical inertia.

Methods: An observational study of IMHU admissions among adolescents aged 11–17 was conducted from 2011 to 2024. Quarterly (Q) admissions were modelled using a pre-pandemic seasonal autoregressive integrated moving average (SARIMA) framework (Q1 2011 to Q1 2020) utilizing all IMHU admission episodes to generate counterfactual forecasts for the period from Q2 2020 to Q4 2024. Excess admissions (observed – expected) were then assessed using a one-sample t-test, an exact binomial test and the proportion of quarters falling outside the 95% forecast confidence intervals (CIs). Univariate and multivariable analyses were also performed on unique patients to compare sociodemographic and clinical characteristics in the pre- and post-pandemic periods.

Results: Between 2011 and 2024, a total of 338 admission episodes across 230 unique patients were recorded. Although hospitalisations had shown an upward pre-pandemic trend, post-pandemic admissions episodes exceeded SARIMA forecasts by an average of 2.71 per quarter (95% CI: 0.43–5.00; p = 0.023). Observed admissions were above the predicted value in 79% of post-pandemic quarters (p = 0.019), while 31.5% of quarters exceeded the upper limit of the 95% forecast CI. Overall, 200 admission episodes were observed compared with 147 expected, representing a relative increase of 36.1%. At the patient level, there was also a significantly higher proportion of adolescent female admissions, a rise in internalising disorders with suicidal behaviour, as well as shorter stays and a greater use of psychopharmacological treatment in the postpandemic period.

Conclusions: Against a background of increasing adolescent IMHU admissions over time, the pandemic period was associated with a significant excess of admissions episodes beyond expected levels, alongside a shift in their clinical profile.