Between January 2018 and January 2019, a total of 1700 young adults, aged 18–35 years, were enrolled in the online national survey using a convenience sampling method. A popular online survey platform in China was utilized, that is, Wenjuanxing (http://www.wjx.cn). The survey recruitment information was posted to six administrative regions in China, including the northeast, eastern, north, south central, southwest, and northwest areas, and the link for the online survey was provided. Participants with a diagnosis of mental illness, such as major depressive disorder, bipolar disorder, psychotic disorders, and others, were excluded from participating. The sample size was determined by the subject to item ratio of 5–10:1 , and the total number of survey items was 166.
2.2.1. Cognitive reactivity
The modified Chinese version of the Leiden Index of Depression Sensitivity (LEIDS-RR-CV) is a 26-item self-report measure of cognitive reactivity to sad mood . Participants are asked to imagine the last time they felt a mild state of dysphoria, and then to indicate the degree to which a list of statements describes their typical cognitions and behaviors in response to a sad mood. The LEIDS-RR-CV contains 26 items from five subscales, including hopelessness/suicidality (HOP), acceptance coping (ACC), aggression (AGG), control/perfectionism (CTR), and avoidant coping (AVC). All of the items are rated using a 5-point Likert-scale (0=not at all to 4=very strongly). Items are all positively worded for CR, and the total score is obtained by summing the scores of all items. A higher total score indicates stronger CR. In this study, the Cronbach’s α coefficient was 0.95 for the overall scale. Huang et al. identified a cut-off score of 60 for LEIDS-RR-CV to screen for healthy individuals at risk for depression in China .
2.2.2. Social support
The Multidimensional Scale of Perceived Social Support (MSPSS) is a 12-item self-report scale used to measure perceived social support from family, friends, and significant others [21,22]. The scale employs a 7-point rating scale ranging from 1 (very strongly disagree) to 7 (very strongly agree). The total scores of the scale range from 7–84, with higher scores indicating greater levels of social support. The social support is classified into low, middle, and high support levels according to the cut-off score ranges of the MSPSS, that is, 12–36, 37–60, and 61–84, respectively . In this study, the Cronbach’s α coefficient was 0.97 for the overall scale.
The Neuroticism Subscale of the Chinese Big Five Personality Inventory (NEO-CBF-PI) I is the most comprehensive self-report questionnaire measuring the five dimensions of personality, including neuroticism. The CBF-PI consists of 40 items and has been extensively validated . The 8-item neuroticism subscale of the CBF-PI is rated on a 6-point Likert scale (1–6), with the total score ranging from 8 to 48. Higher scores are indicative of a higher level of neuroticism. Based on previous studies , levels of neuroticism are classified into high and low according to the cut-off score of 36 for the CBF-PI. In this study, the Cronbach’s α coefficient was 0.87 for the NEO-CBF-PI.
The Chinese version of the 14-item Resilience Scale (RS-14) developed by Wagnild and Young is one of the most reliable tools in measuring resilience in various age groups and different conditions [24,25]. It is composed of 14 items representing the “Personal Competence Factor” and “Acceptance of Self and Life Factor.” Each item is graded from 1 (strongly disagree) to 7 (strongly agree). Graded items are summed to provide a total score, in which lower scores indicate less resilience. According to the cut-off value of 74, resilience levels are classified into high and low . The Cronbach’s α of the RS-14 was 0.96 in this study.
The Self-Compassion Scale (SCS) is the most commonly used scale to measure self-compassion at times of perceived difficulty . It is composed of 26 items and six subscales, including self-kindness, self-judgment, common humanity, isolation, mindfulness, and over-identification. Each item rated on a 5-point Likert-type scale for frequency (1=almost never; 5=almost always). The total score is calculated through the average of the individual subscales, and all negatively scored items are transformed. Levels of self-compassion are classified high and low according to the 75% of total scores of SCS (130*0.75) as based on a previous study , that is, a score of 98. In this study, the Cronbach’s α of the scale was 0.77.
2.2.6. Life events
The 48-item Life Events Scale (LES) is used to evaluate negative and positive life events that have occurred during the previous year or longer, including family, work or study, social related events . Each of the 48 life event items was anchored to four questions: (i) when it happened, measured by “never,” “in the past 1 month,” “in the past 1 year or longer”; (ii) whether it was positive or negative for the target person; (iii) the impact on the target person’s mental health, measured by a 5-point scale ranging from “no impact” to “very severe impact”; (iv) the duration of the event, measured by a 4-point scale ranging from “3 months,” “6 months,” “≤1 year” to “longer.” The intensity of each life event is calculated by the impact multiplied by the duration and then by the timeframe in which it happened. The total intensities of positive and negative life events are summed by the score of each positive or negative life event. Based on the 75% of this score (Fang et al., 2013), the total intensities of positive and negative life events are further classified into high and low levels. In this study, the Cronbach’s α of the scale was 0.94.
2.2.7. Socio-demographic characteristics
Participants were asked about their residential area and location, age, sex, marital status, educational level, religion, monthly household income (Yuan, RMB), employment status, smoking status, living status, BMI, family history of mental illness, whether they had previously experienced depression, the frequency of sad mood in the past month, and their sleep quality.
All procedures were approved by the ethical committee of Fujian Medical University (NO: FMU2017024), and informed consent was obtained from all participants. The study adhered to the STROBE (Strengthening the Reporting of Observational studies in Epidemiology) statement . All measures were completed via the Wenjuanxing platform. The Questionnaire completion time was approximately 20 min, and the questionnaire could not be effectively submitted when less than half complete or with repeated answers. Participants who completed the survey were remunerated with a RMB 10 gift card.
2.4. Statistical analysis
Data analyses were conducted using SPSS 24.0 (IBM, Armonk, NY, USA). Missing data were replaced using mean value substitution, and p<0.05 was considered statistically significant. The data meet the assumptions of normality as the one sample Kolmogorov-Smirnov tests were not statistically significant. Continuous variables are expressed as means and standard deviations (SDs). Categorical variables are expressed as proportions or percentages.
Young adults with a LEIDS-RR-CV total score <60 were considered the normal group (NG), while those with a score ≥60 were considered the risk for depression group (RDG).
We took three analysis steps to determine the influencing factors of CR. First, univariate analyses were employed; chi-square and independent t-tests were used to compare the differences in socio-demographic variables, self-compassion, resilience, social support, neuroticism, and life events between the two groups. Second, the collinearity of the independent variables was examined by the variance inflation factor (VIF) before conducting binary logistic regression. The VIF of the 11 variables ranged from 0.45–2.63 (which should ideally be <4.0), suggesting no violations of the regression assumptions . Third, the binary logistic regression with a forward conditional method was conducted to determine the influencing factors associated with CR. The dependent variable was whether the young adults were at risk for depression. The variables shown to be statistically significant in the independent t-test or chi-square test were input as independent variables.