Associations Between Sleep Problems And Non-suicidal Self-injury In Adolescents And The Mediating Roles Of Depression And Externalizing Problems

BackgroundNon-suicidal self-injury(NSSI)is defined as direct and intentional bodily destruction without suicidal intent,the purpose of which is not socially acceptable.Deliberate self-harm includes NSSI and suicide attempt,and the two behaviors are different in presence of suicidal intent.NSSI has recently been proposed as a new diagnostic category within DSM-V considering the differences between the two behaviors,but previous studies mainly focus on suicide behavior or deliberate self-harm.NSSI does not usually lead to serious medical outcomes but tended to be repeated and increases the risk of a fatal outcome.Previous studies have found that NSSI is an important risk factor for suicide death.NSSI is particularly prevalent among adolescents,globally,the prevalence of NSSI in the past year among adolescents is about 19.5%.Hence,NSSI is an important public health issue.NSSI among adolescents is recognized gradually by more and more scholars both at home and abroad because of the high incidence,recurrence,and long-term clinical risk.There are only a handful of countries that have established hospital-based surveillance systems for self-injury,and most people who injure themselves don't present at a hospital because of the nonfatal medical outcomes and the social stigma of self-injury,so most cases are concealed and unreported,which may lead to an incomplete picture of self-injury just like the tip of the iceberg.Therefore,it is of great importance for public health to carry out epidemiological surveys in the community to explore the basic characteristics and associated factors of NSSI among adolescents.There are some studies on the prevalence,methods,and associated factors of NSSI in adolescents,but few studies focus on the age at onset,medical severity,age and gender differences of NSSI in adolescents.Previous cross-sectional studies have shown that NSSI is typically initiated at early adolescence with a low prevalence,peaks in mid-adolescence,and then gradually decreases at the end of adolescence.To accurately grasp the dynamic trend of the risk of NSSI in adolescents,that is how NSSI develops and changes during adolescence,longitudinal follow-up studies are still needed.Besides,exploring the heterogeneity of the dynamic trend of NS SI in adolescents over time may contribute insight into the different pathogenesis or prognosis of NSSI and to developing more targeted prevention and intervention measures.Despite multiple factors are associated with increased risk of NSSI,there is a paucity of evidence of effective interventions.Further investigation about modifiable risk factors of NSSI is required.Sleep patterns change significantly during adolescence.Good sleep quality provides important guarantees for adolescent growth and development and the realization of daytime functions.In the meanwhile,sleep problems are relatively easy to identify and intervene.However,studies associating sleep problems and NSSI in adolescents are limited and the results have been mixed due to differences in sample,measurement,study design,and focusing on different sleep problems.The process driving the sleep problems-NSSI link is not clear.Besides,sleep problems may be highly correlated or overlap,it is essential to examine which sleep variables are significant and independent predictors of NSSI after controlling for other sleep variables.ObjectivesBased on previous research and the basis of our previous work,there are three aims in the current study:1.Describe epidemiological characteristics of NSSI in adolescents such as onset age,medical severity,age-and gender-specific differences in characteristics of NSSI,the longitudinal trajectories,and the developmental heterogeneity of NSSI with the cross-sectional and longitudinal study design.2.After adjusting for demographics,psychological factors,physical and behavioral factors,and social factors,examine the independent effects of different sleep problems,including frequent nightmare,insomnia,sleep inefficient and daytime sleepiness,on NSSI and longitudinal trajectories of NSSI based on the cross-sectional and longitudinal study design.3.Investigate the longitudinal associations and potential mechanisms between sleep problems and NSSI with a three-wave longitudinal design,that is,the potential mediating role of depression and externalizing problems on the sleep problems-NSSI link,and the moderating role of gender and grade in each theorized path of the mediating model.Methods1.Data collectionThe participants were recruited from three counties of Shandong province(Zoucheng,Yanggu,and Lijin)by the convenient cluster sampling method.According to the number of students of each school,2-3 schools in each county were chosen to carry out the survey,including at least one senior high school and one junior high school.Demographic and sociological factors,physical and behavioral health factors,NSSI,sleep problems(frequent nightmares,insomnia,daytime sleepiness and sleep duration),and psychological factors were measured using the adolescent health questionnaire.In November-December of 2015,the baseline survey with a self-administered questionnaire was conducted among 7th-11th graders in target schools,and a total of 11831 valid questionnaires were collected.During the same periods in 2016 and 2017,a total of 6995 7th and 10th graders at baseline were followed up for the first and second time,respectively.2.Statistical analysisSPSS(version 24.0)and Mplus(version 8.3)were used for the following analyses:(1)The prevalence and epidemiological characteristics of NSSI and sleep problems were described.The overall development trajectory and the developmental heterogeneity of NSSI during the study period were examined respectively using the latent growth curve model and the latent class growth analysis.Based on model evaluation indexes such as the information criterion,likelihood ratio test,entropy value,and the practical significance of the model,the optimal number of NSSI developmental trajectories was determined.(2)Using cross-sectional and longitudinal study data,the multivariate binary Logistic regression and the multivariate multinomial Logistic regression based on the three-step approach with adjustment for classification errors were carried out to explore the independent effects of different sleep problems on NSSI and the latent class of NSSI trajectories.In the regression analyses,the missing values and model parameters were estimated using full information maximum likelihood and robust maximum likelihood.(3)The hypothesis that T0 sleep problems(predictor)?T1 depression or externalizing problems(mediator)? T2 NSSI(outcome)was developed based on cross-lagged panel model with longitudinal study data.At the same time,considering the effect of time lag on causal inference,another hypothesis that T0 sleep problems(predictor)?T1 depression/externalizing problems(mediator)T1 NSSI(outcome)was also presented.Improved causal steps approach was used to verify the two hypotheses.Multi-group structural equation model was used to verify the moderating effect of gender and grade.Results1.At baseline,a total of 11831 students attended the survey,including 50.9%boys,and the mean age is 14.97±1.46 years.The prevalence of lifetime NSSI was 19.2%and 13.0%in the past year.Overall,the reporting rate of NSSI was higher in women than in men,but the reporting rate of NSSI was higher in men than in women for 11th graders.The reporting rate of NSSI in the past year increased gradually and then decreased by grade increase.The median onset age of NSSI was 13 years,ranging from 12 to 15.About 7%of cases required medical treatment,and the consultation rate in male cases was twice as much as the female cases(9.7%vs.4.4%).The average sleep hour of the participants was 7.2 hours,and 71.3%of the participants slept less than 8 hours.The prevalence of insomnia,frequent nightmares and moderate/severe daytime sleepiness were 14.7%,8.7%,and 21.7%respectively.2.Based on cross-sectional data analyses,insomnia(AOR=1.05,P<0.001),frequent nightmares(A OR=1.35,P=0.001),insufficient sleep(AOR=1.19,P<0.001)and daytime sleepiness(AOR=1.02,P<0.001)were all independent factors of NSSI after adjustment for demographic,physical and behavioral factors,and sociological factors.With additional adjustment for depression and externalizing problems,frequent nightmares(AOR=1.15,P=0.138)and daytime sleepiness(AOR=1.00,P=0.557)were no longer significantly associated with NSSI,however,insufficient sleep(AOR=1.20,P<0.001)and insomnia(AOR=1.02,P=0.003)were still significantly associated with NSSI.3.Using three waves data of baseline 7th and 10th graders,it was found that the overall risk of NSSI declined over time(B slope=-0.73,P<0.001)using latent growth curve model.The analysis by grade shown that the risk of NSSI was stable in grade 7(B slope=-0.36,P=0.194),and the initial risk level of NSSI was higher in grade 10 then significantly declined(B slope=-0.93,P<0.001).To further explore the heterogeneity of the development trajectory of NSSI,latent class growth analysis was performed and found that there were three potentially distinct subgroups in the NSSI developmental trajectory of the sample including the low risk group(72.7%),the moderate and significantly declined risk group(25.3%)and the moderate and significantly increasing risk group(1.9%).According to an analysis by grade,there were three potentially distinct subgroups in the development of NSSI risk in 10th graders:low risk group(84.0%),chronically low and moderate risk group(10.6%)and high and significantly declined risk group(5.4%).There were two potentially distinct subgroups in the development of NSSI risk in 7th graders:the low risk group(89.8%)and the moderate risk group(10.2%).4.To explore the influence of various sleep factors on the development trajectory of NSSI using three waves data of baseline 7th and 10th graders.Results showed that students with frequent nightmares(AOR=2.59,P=0.044)had a higher risk of following the moderate and significantly increasing risk group,students with insufficient sleep(AOR=1.45,P<0.001),insomnia(AOR=1.05,P<0.001)and daytime sleepiness(AOR=1.03,P=0.002)were at higher risk of entering the moderate and significantly declined risk group after adjustment for demographic factors,physiological and behavioral factors,and sociological factors.With further adjustment for depression and externalizing problems,the effect of insufficient sleep on the longitudinal development of NSSI in adolescents was still significant,that is,students with insufficient sleep were more likely to follow the moderate and significantly declined risk group(AOR=1.47,P<0.001).Frequent Nightmares(AOR=2.14,P-0.098),insomnia(AOR=1.02,P=0.080)and daytime sleepiness(AOR=1.01,P=0.546)had no significant effect on the longitudinal development of NSSI in adolescents.5.With adjustment for demographic factors,physical and behavioral health factors and sociological factors,T0 frequent nightmares and insufficient sleep were significant predictors of T1 NSSI(frequent nightmares:AOR=1.51,P=0.008;insufficient sleep:AOR=1.19,P=0.013)and T2 NSSI(frequent nightmares:AOR=1.67,P=0.009;insufficient sleep:AOR=1.15,P=0.007),however,there was no significant correlation between T0 insomnia and daytime sleepiness and T1 or T2 NSSI(Ps>0.05)after controlling for covariates.The mediation analysis showed that T1 depression played a significant mediating role between T0 frequent nightmares and T1 NSSI(?ab=0.009,95%CI=0.003-0.015)after controlling for covariates,and the ratio of mediation effect was 22%.The mediating effect of T1 depression between T0 frequent nightmares and T2 NSSI was also significant(?ab=0.005,95%CI=0.001-0.010)after controlling for covariates,and the ratio of mediation effect was 6.4%.Multi-group structural equation models results showed that the moderating effect of grade on the direct effect of T0 frequent nightmares?T2 NSSI was significant(?=-0.92,95%CI:-1.73,-0.11),with further adjustment for covariates,the moderating effect(?=-0.74,95%CI:-1.61,0.12)was not significant.The mediation effect of depression between insufficient sleep?NSSI and the mediation effects of externalizing problems between frequent nightmares?NSSI and insufficient sleep? NSSI were all not significant in different lag periods.Conclusions1.The prevalence of NSSI was high among adolescents and the onset age of NSSI was early.NSSI cases were often concealed due to most cases would not present to the hospital.It is necessary and urgent to prevent adolescent NSSI.Compared with the female,the onset age of NSSI for males was much earlier,the consultation rate of male NSSIs was lower and the prevalence of NSSI in later adolescence was higher,so attention should also be paid to NSSI among males.2.From a horizontal perspective,the prevalence of NSSI in 7th-11th graders increased gradually and then decreased.From a longitudinal perspective,the overall developmental trend of the NSSI risk decreased over time,and there were three discrete NSSI trajectories including low class,moderate and declined class,and moderate and increased class.The NSSI risk for 7th graders was stable during 2 years follow-up,and the NSSI risk for 10th graders was relatively high at the beginning.It suggested that great emphasis should be placed on individual heterogeneity,focusing on high-risk groups,and developing targeted prevention and control interventions.3.Frequent nightmares,insufficient sleep,insomnia,and daytime sleepiness were significantly associated with NSSI in adolescents.Adolescents with frequent nightmares were more likely to enter into moderate and increased class and frequent nightmares and insufficient sleep are independent risk factors of adolescent NSSI.Depression played a significant mediating role in the associations of frequent nightmares and NSSI.The moderating role of gender and grade in each path of the mediating model was not significant.The significant mediating role of externalizing problems in frequent nightmares/insufficient sleep-NSSI link was not founded in this study.The mechanism of insufficient sleep on NSSI in adolescents still needs to be further explored.It is suggested that assessing and intervening in sleep problems and depression may have important implications for preventing adolescent NSSI.SignificanceThis study analyzed the characteristics,development trajectory,and potential subgroups of trajectories of adolescent NSSI.The results enhanced understanding of adolescent NSSI and provided decision-making bases for assessing the risk of NSSI among adolescents with different characteristics or at different stages of development.By exploring the relationships between multiple sleep problems and NSSI,the mediating roles of depression and externalizing problems,and the moderating role of gender and grade,the findings can provide targets and evidence for society,family and schools to develop and carry out adolescent self-injury prevention and intervention project.Innovation1.Based on large-sample size cross-sectional and longitudinal surveys and the comprehensive consideration of demographic and sociological factors related to NSSI,this study systematically and comprehensively evaluated the effect of different sleep problems on NSSI,which ensured to obtain actual and reliable results.2.This study detected the longitudinal trajectories,the developmental heterogeneity,and related factors of NSSI trajectory heterogeneity of NSS in adolescents.The results provided important consults for understanding NSSI,identifying high-risk individuals,and taking personalized prevention measures from the developmental perspective.3.By constructing the longitudinal mediation model of sleep problems?depression/externalizing problems?NSSI and validating the moderating effects of gender and grade,this study revealed the mediating role of depression between frequent nightmares and NSSI.This finding had significant enlightenment for the intervention of adolescent NSSI.