Cross-national research on the mental health of adolescents is essential for understanding the unique challenges they face, identifying trends and risk factors, and ultimately promoting positive mental health outcomes on a global scale during this critical stage of development. The thesis aims to broaden the knowledge of mental health problems among adolescents with a specific focus on perceived school safety, help-seeking behavior for mental health problems, cyberbullying and suicide attempt in a large-scale international study of 13 countries in Asia and Europe.

First, a systematic literature review was conducted to synthesize the findings of the existing literature on perceived school safety. The following three studies were part of the school-based cross-national Eurasian Child Mental Health Study. This cross-national study included 21,688 adolescents aged 13–15 (50.8% girls) from 13 Asian and European countries (China, Finland, Greece, India, Indonesia, Iran, Israel, Japan, Lithuania, Norway, Russia, Singapore, and Vietnam) who completed self-administered surveys between 2011 and 2017. Logistic regression analyses were used to estimate odds ratios and 95% confidence intervals.

The systematic review, including 43 papers, revealed that 6.1–69.1% of students felt unsafe at school, and it was associated with various factors such as victimization and mental health issues. The cross-national study showed that 31.4% of adolescents felt unsafe at school. Strong associations were found between feeling unsafe and bullying victimization, mental health problems, and lack of teacher support. The use of formal help among adolescents was notably low, particularly in lower-income countries. Girls were generally more likely to seek help than boys. The prevalence of suicide attempt was 4.8%, and the rate was higher among girls. Victims of both cyber and traditional bullying had the highest suicide attempt risk, and emotional symptoms moderated the association.

The thesis reveals the important cross-national differences in the mental health and related behavior of adolescents. The findings highlight the need for global efforts to address adolescent mental health needs. Possible approaches to tackle the issue are a stepped-care model including school-based mental health promotion programs, anti-bullying interventions and digitalized mental health interventions.