The trajectories and associations of insomnia symptoms with addictive behaviours in adolescents: A two-year longitudinal study.

Insomnia displays heterogeneous trajectories across adolescence, which may induce addictive behaviours, including internet gaming disorder and substance use. This study aimed to investigate the latent trajectory classes of insomnia symptoms over 2 years and to examine the associations between insomnia trajectories and these addictive behaviours. Participants were 910 adolescents from six middle schools in Shanghai, China (52.7% males; mean age = 13.17 years). The three-wave survey measured insomnia symptoms, internet gaming disorder, substance use, depressive symptoms, and sociodemographic characteristics from 7th to 9th grade. Latent class growth modelling was performed to identify the latent trajectory classes of insomnia symptoms. Then multivariable logistic regressions were conducted within the best-fitting latent class growth model to examine the associations of insomnia trajectories with internet gaming disorder and substance use. Two latent trajectory classes of insomnia symptoms were recognised: the non-insomnia group (71.8%) and the insomnia group (28.2%). In the multivariable analysis controlling for baseline demographic variables and depressive symptoms, the insomnia group had a higher risk of developing internet gaming disorder (OR = 2.203 [95% CI: 1.258-3.858]) and substance use (OR = 2.215 [95% CI: 1.324-3.705]) compared with the non-insomnia group. These findings add to a growing body of research on heterogeneous trajectories of insomnia symptoms during adolescence, suggesting that intervention strategies are needed to target the characteristics or developmental patterns of different insomnia subgroups. The ultimate goal is to mitigate the impact of insomnia symptoms on adolescent addictive behaviours.