Loneliness mediates the association between sleep deficiency and fighting in school-aged adolescents: a 2-year longitudinal study.

Sleep deficiency is becoming increasingly common among adolescents and may lead to aggressive behaviour. This study investigated the association between sleep deficiency and fighting among 1946 school-aged adolescents (mean age: 12.2 ± 0.47 years) in Ningbo city through a two-year longitudinal study and explored the mediating roles of loneliness, sadness, and nervousness. A total of 552 (28.3%) reported sleep deficiency at baseline. During the follow-up period, 347 (17.8%) adolescents engaged in fighting. Sleep deficiency was significantly associated with an increased likelihood of fighting (OR: 1.91, 95% CI: 1.45-2.52) after adjusting for confounders. Compared with boys, girls with sleep deficiency presented a greater risk of fighting (OR: 2.61, 95% CI: 1.44-4.73 for girls; OR: 1.74, 95% CI: 1.27-2.39 for boys). This association persists among adolescents with unhealthy lifestyles. Loneliness partially mediated this relationship (indirect effect β = 0.013, P < 0.05, effect ratio = 12.26%), whereas sadness and nervousness had no significant mediating effect. Studies have shown that sleep deficiency independently predicts adolescent fighting behaviour, with loneliness playing a key mediating role. Interventions that improve sleep hygiene, reduce loneliness, and address lifestyle likelihood factors may help reduce violent behaviour in adolescents.