Research Design
This study utilized a cross-sectional research design to investigate the relationships among SE, CS, SQ, and DS in adolescents. The analysis specifically examined the correlations between these variables, with a particular focus on the potential mediating effects of CS and the moderating effects of SE on the relationship between SQ and DS.
Study Population
Data were gathered from 1,200 junior high school students enrolled in three middle schools within a single province in China, between January and June 2023. After excluding responses that did not meet the study’s rigorous criteria, 1,132 valid questionnaires were retained for subsequent analysis. Inclusion criteria mandated that participants demonstrate good mental health, possess normal literacy and comprehension abilities, be free from serious physical illnesses, and provide informed consent from both themselves and their guardians, thereby ensuring voluntary participation.
Data Collection and Quality Assurance
To uphold the integrity of the data collection process, all investigators underwent standardized training prior to questionnaire distribution. Each questionnaire was collected using anonymous numbering to ensure that no identifying information about participants was recorded or identified. The questionnaire was accompanied by a separate consent form that participants were asked to take home and have their guardian read and sign before completing the questionnaire. If the guardian did not consent, the participant would not complete the questionnaire. The consent form was only used to ensure that participants' participation in the study was voluntary, and the questionnaire itself was anonymized for data collection and did not contain any personally identifiable information. Completed questionnaires were collected by investigators the following day. To ensure data accuracy, a two-person data entry and verification process was implemented, complemented by a third person who randomly checked 20% of the questionnaires to further validate the accuracy and reliability of the data entry process.
Research Tool
The Self-Rating Depression Scale (SDS)
The SDS is a widely utilized tool for assessing depressive symptoms, encompassing emotional, somatic, and psychological dimensions(20). This instrument comprises items rated on a 4-point Likert scale, ranging from 1 ("never") to 4 ("often"), with higher scores indicating more severe depressive symptoms. A score of 53 or above serves as the threshold for identifying the presence of depressive symptoms. In this study, the SDS functioned as the dependent variable for evaluating DS in relation to SQ and CS, exhibiting a Cronbach's alpha of 0.836, indicating good internal consistency.
The Pittsburgh Sleep Quality Index (PSQI)
The PSQI is a standardized measure for assessing sleep quality(21). It evaluates seven components: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction. Each component is scored from 0 to 3, yielding a total score between 0 and 21, where higher scores signify poorer sleep quality. In this study, the PSQI was employed as the independent variable to explore the association between SQ and DS, with a Cronbach's alpha of 0.902, reflecting excellent reliability..
The General Self-Efficacy Scale (GSES)
The GSES assesses an individual's belief in their capability to navigate challenging situations(22). The scale consists of items rated on a 4-point Likert scale, with higher scores denoting stronger self-efficacy. In this study, the GSES was used as a moderating variable to examine its influence on the relationship among CS, SQ, and DS. The GSES exhibited a Cronbach's alpha of 0.908, demonstrating high reliability.
The Simplified Coping Style Questionnaire (SCSQ)
The SCSQ evaluates coping mechanisms and comprises two dimensions: active response (SCSQ.AR) and negative coping (SCSQ.NC)(23). Each item is scored on a 4-point Likert scale, ranging from 1 ("never") to 4 ("often"). SCSQ.AR is generally associated with improved mental health outcomes, whereas SCSQ.NC is linked to heightened psychological distress. In this study, the SCSQ served as a mediating variable to assess its impact on the relationship between SQ and DS, achieving a Cronbach's alpha of 0.866, indicating of good internal consistency.
Data Analysis
Data analysis was conducted using IBM SPSS 25 and the PROCESS macro developed by Hayes, incorporating a comprehensive array of statistical techniques. These techniques included descriptive statistics, correlation analysis, partial correlation analysis, regression analysis, mediation analysis, and moderated mediation analysis.
Descriptive statistics were employed to summarize the sample characteristics, calculating medians and interquartile ranges. Non-parametric tests were also utilized to compare differences between depressive symptom subgroups, providing preliminary insights into the distribution and characteristics of the study variables.
Spearman's correlation coefficients were calculated to explore the relationships among key variables, including SDS, PSQI, SCSQ, and GSES. To account for potential confounders, partial correlation analyses were performed while controlling for demographic variables such as academic performance and family income.
Spearman's correlation coefficients were calculated to explore the relationships among key variables, including SDS, PSQI, SCSQ, and GSES. To account for potential confounders, partial correlation analyses were performed while controlling for demographic variables such as academic performance and family income.
Utilizing the PROCESS macro (Model 4) established by Hayes, mediation analysis examined the roles of SCSQ and GSES in the relationship between PSQI and SDS. A bootstrap sample of 5,000 iterations was employed to estimate the indirect effects, with significance tests and bootstrap confidence intervals (CIs) determining whether SCSQ.AR, SCSQ.NC, and GSES partially or fully mediated the impact of PSQI on SDS.
The PROCESS macro (Model 8) was employed for moderated mediation analysis to investigate whether GSES moderated the mediating effect of SCSQ in the PSQI-SDS relationship. Path coefficients were assessed at varying levels of GSES to elucidate its moderating role within these mediational pathways. The moderation effect was analyzed by evaluating how the interaction between GSES and PSQI influenced the indirect effects via SCSQ on SDS.