Despite the impact that the COVID-19 pandemic had on adolescents' mental health, there is a lack of studies comparing it pre- and postpandemic using consistent designs and measurements. Therefore, this study aimed to analyze changes in adolescent psychopathology, deliberate self-harm behavior, substance use, and help-seeking behavior pre- and post-COVID-19, with an identical study design.

The study included three repeated cross-sectional studies conducted in 2014, 2018, and 2023, including self-reported data from Finnish secondary school students in grades 7 to 9, aged 13 to 16 (n = 9,024). The survey measured demographic information, mental health using the Strengths and Difficulties Questionnaire (SDQ), deliberate self-harm behavior, substance use, and help-seeking behavior.

Comparing data in 2023 with 2018, there were significant increases among females in total SDQ score (OR 2.1, 98.33% CI 1.7–2.7), conduct problems (OR 1.7, 98.33% CI 1.1–2.7), emotional symptoms (OR 1.8, 98.33% CI 1.5–2.3), and hyperactivity symptoms (OR 2.8, 98.33% CI 2.2–3.6). Perceived severe overall difficulties (OR 2.8, 98.33% CI 2.0–3.7), weekly smoking (OR 2.7, 98.33% CI 1.5–4.9), and seeking help (OR 1.5, 98.33% CI 1.2–2.0) increased. For males, increases were noted only in hyperactivity symptoms (OR 2.5, 98.33% CI 1.2–1.9) and perceived severe overall difficulties (OR 1.5, 98.33% CI 1.0–2.1), along with a decrease in alcohol consumption (OR 0.7, 98.33% CI 0.5–0.9). By contrast, the period from 2014 to 2018 showed minimal changes.

The concerning rise in psychopathology after the COVID-19 pandemic, particularly among females, highlights the importance of early detection and effective interventions.