Abstract Background Elevated loneliness experiences characterise young people. While loneliness at this developmental juncture may emerge from age‐typical upheaval in social relationships, there is little data on the extent to which young people experience high and persistent levels of loneliness, and importantly, who is most vulnerable to these experiences. Using the widespread social restrictions associated with the COVID‐19 pandemic, which precipitated loneliness in many, we aimed to examine adolescents' loneliness profiles across time and the demographic predictors (age, sex, and country) of more severe trajectories. Methods Participants aged 12–18 years, recruited into a multi‐wave study (N = 1039) across three sites (UK, Israel, and India) completed a 3‐item loneliness measure fortnightly across 8 timepoints during the pandemic. Results Latent class growth analysis suggested 5 distinct trajectories: (1) low stable (33%), (2) low increasing (19%), (3) moderate decreasing (17%), (4) moderate stable (23%), and (5) high increasing (8%). Females and older adolescents were more likely to experience persistently high loneliness. Conclusions These findings indicate a need for interventions to reduce loneliness in adolescents as we emerge from the pandemic, particularly for those groups identified as being at highest risk.
