Trajectories of loneliness in Canadian adolescents over the COVID-19 pandemic.

Increases in adolescent loneliness were a significant concern during the lockdowns of the COVID-19 pandemic. We use longitudinal survey data from the Cannabis Use, Obesity, Mental Health, Physical Activity, Alcohol Use, Smoking, and Sedentary Behavior study from 2017 to 2023 to assess whether increases in loneliness correspond to lockdowns, whether different cohorts differ in the trajectories of loneliness ratings and whether social support and relationships impact the course of loneliness throughout secondary school. We compared linear latent growth models and latent basis growth models of annual repeated measures of loneliness from three 4-year cohorts of Canadian high school students (N = 5,237, female = 3,166, 80.42% White). For the 2017-2021 cohort, a linear model fit best, while nonlinear models were the best fit for the 2018-2022 and 2019-2023 cohorts. Ratings of loneliness were highest at the beginning of the COVID-19 pandemic across all three cohorts and stabilized in the years following. Growth mixture models identified groups with differing trajectories of loneliness where lowest loneliness was associated with positive relationship quality of family and friends. Overall, the study demonstrated heterogeneity in loneliness trajectories across time between and within cohorts. The patterns were consistent with increases during COVID-19 lockdowns and a return to typical levels as social restrictions eased. (PsycInfo Database Record (c) 2026 APA, all rights reserved).