Loneliness is a well-established correlate of adolescent suicidal ideation, yet prior cross-national studies have mainly quantified average associations with suicidal behavior. Less is known about whether loneliness occupies the same position within broader suicide-risk networks across societal contexts. Using cross-sectional data from the public World Health Organization Global School-based Student Health Survey from 87 countries (N = 439,026; 52.1% female), we examined cross-national variation in the network position and predictive role of loneliness. Stage-specific samples were 317,141 adolescents from 64 countries for network estimation, 333,940 adolescents for prediction transfer, 42 countries for feature-importance screening, 296,863 adolescents from these countries for multilevel models, and 38 countries for edge analyses. Suicidal ideation was consistently among the most central nodes, but prediction models transferred poorly across regions, with a 17.3 percentage-point loss in area under the curve. Loneliness showed the greatest cross-context variation among predictors. Across 11 macro-level indicators, national urbanization had the strongest association with loneliness's model-based importance (Spearman r = .655, p < .001 after false discovery rate correction). Individual-level models indicated a stronger association between loneliness and suicidal ideation in more urbanized countries (odds ratio = 1.096, 95% confidence interval [1.053, 1.140]), and country-level network models revealed stronger loneliness-suicidal-ideation edges where urbanization was higher (Spearman r = .639). These findings suggest that loneliness may become more tightly connected to adolescent suicide risk in more urbanized social contexts.

Adolescent suicide;Network analysis;Urbanization;Cross-cultural comparison;Loneliness; Global School-based Student Health Survey