Detecting loneliness among late adolescents: Validation and testing of a detection tool based on the UCLA Loneliness Scale

The high prevalence of loneliness among adolescents, combined with their tendency to conceal it, highlights the need for strategies that identify and support those youth who experience loneliness. This study aimed to validate and test a detection tool for late adolescents within educational settings in Denmark. The tool, which was based on nine items from the UCLA Loneliness Scale (UCLA-9), underwent a three-stage refinement and testing process. In Stage 1, psychometric analyses and cognitive interviews investigated the reliability, validity, and usability of the tool among adolescents ages 16–20 years; potential cut-off scores for identification of cases on the three-dimensional scale were explored. Stage 2 involved a feasibility test in three educational institutions. Field observations and qualitative interviews with participants offered insights and recommendations for implementation of the tool in educational settings. Stage 3 involved 1728 students engaged in the Danish Lift program run in three municipalities. Among those youth, the refined UCLA-9 demonstrated robust psychometric properties, identifying 9% of adolescents as cases with a cut-off score of ≥10 on each subscale. The UCLA-9 showed promise in identifying adolescents experiencing loneliness, which often co-occurred with poor mental health. Challenges remain in determining appropriate cut-off scores for the identification of cases.