Depression as a mediator between frequent nightmares and non-suicidal self-injury among adolescents: a 3-wave longitudinal model

Background: Frequent nightmares and depression are associated with non-suicidal self-injury (NSSI) in adolescents. Little is known about the mediating role of depression in the nightmare-NSSI link. This study explores the longitudinal mediating effect of depression on the relationship between frequent nightmares and NSSI as well as the moderating effect of gender using a three-wave longitudinal design. Methods: Participants were adolescents from the Shandong Adolescent Behavior and Health Cohort who were surveyed at baseline, 1 year later, and 2 years later. A self-administered questionnaire was used to measure nightmare frequency, depression, and NSSI. Structural equation modeling and multiple-group analysis were used to test the mediating effect of depression and the moderating effect of gender. Covariates included demographics and earlier measures of depression and NSSI. Results: Among 6995 participants, 3399 (48.6%) were females, mean age was 14.86 (SD = 1.50) years at baseline. Frequent nightmares had a significant mediation effect on NSSI through depression (B_ab = 0.06, 95% CI = 0.02–0.10) after controlling for demographics and earlier measures of depression and NSSI. Gender had no significant moderating effect on the nightmare-NSSI association. Limitations: All data were collected by self-report. Conclusions: The association between frequent nightmares and NSSI in adolescents was partially mediated by depression. Frequent nightmares and depression should be assessed and treated to prevent self-harm in adolescents.