The reporting of this study follows the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) guidelines [12] (Additional file 1)
Sample And Study Design
The study was a cross-sectional secondary analysis of data from the baseline survey in 2015 of Taiwan Adolescent to Adult Longitudinal Study (TAALS). The longitudinal nation-wide study employed a multistage, stratified area, probability sampling design to recruit participants from high schools. The methodology of the study has been described in detail elsewhere [13]. First-year students in junior high schools, senior high schools, vocational high schools were eligible for inclusion in the survey. Students who could not provide the informed consent form with their parents’ autographs were excluded from the survey. The TAALS final sample included 173 schools, 1473 class from which 6903 seventh graded students aged 13 years in junior high schools and 11742 tenth grade students aged 16 years in senior high schools and vocational high schools were selected. For this study, data on 18509 participants who fully responded to depressive symptoms questions was used to analyze. Chi-square tests for sample proportions were performed to confirm the representativeness and the similarity between respondents and non-respondents[13]. During an interview, information was collected on sociodemographic, lifestyle and physical activity, substance use, dietary behaviors, mental health, violence-related behaviors and experiences, sexual behaviors and attitudes, and social support. Ethics approval was approved by the Joint Institutional Review Board of Taipei Medical University, Taiwan (TMU-JIRB-201410043) [13].
Measures
Substance use
This study investigated adolescents’ binge drinking, cigarette smoking, e-cigarette smoking and betel chewing. We utilized the criterion of 5 drinks on one occasion for at least one day within the last 30 days to define binge drinking behavior in adolescents[14]. Cigarette and e-cigarette smoking was determined (yes/no) based on self-reported frequency of smoking during the last month[15]. Betel chewing behavior was dichotomously coded as betel chewers or never chewers based on the response “never chew betel nut ever”[16].
Depressive symptoms
Information on adolescent depressive sumptoms was collected during an on-site self-administered survey assisted with a class-based interview system. We analyzed responses to five questions from the Chinese version of the Center for Epidemiological Studies Short Depression Scale (CES-D) [13, 17], namely: How often have you felt this way during the past week (1) - I did not feel like eating; my appetite was poor; (2)- I had trouble keeping my mind on what I was doing; (3) - I felt depressed; (4) - I felt that everything I did was an effort.; (5)- I felt lonely (Cronbach’s α = 0.76). Each item rated a 4-point Likert-type scale ranging from 0:Rarely or none of the time (less than 1 day), 1:Some or a little of the time (1-2 days), 2:Occasionally or a moderate amount of time (3‐4 days), 3:All of the time (5‐7 days). The possible range is from 0 to 15, and a cutoff score of five or higher indicates the presence of depressive symptoms [17, 18].
Screen use
The question “How long have you spent watching TV, playing video games, using a computer, and playing with your mobile phone on average per day during the past seven days?” measured screen use. A cutoff value of two hours or more per day indicates the presence of screen use as “high”(≥ 2 hours per day) and “low” (< 2 hours per day) [8].
Controlling factors
We measured participants' weight (kg) and height (cm) to one decimal point by the digital scales to calculate BMI. The Taiwan Ministry of Health and Welfare classifies BMI status as "underweight" (BMI < 18.5), “normal” (18.5 ≥ BMI < 24), and “overweight or obese” (BMI ≥ 24) [19] according to a WHO Expert Consultation for Appropriate Body-Mass Index for Asian Populations [20]. We divided the frequency of skipping breakfast into two categories: "low" (0–2 times/week) and "high" (3 times/week) depending on how many times the participant reported these actions during the last week.
Socio determinants
Personal characteristics involved sex, age, and school type (junior high school, senior high school, or vocational high school) were determined using self-reported survey responses. The 4-point Likert-type responses to four statements, such as "My classmates/friends care about what happens to me" (range 4–16, cutoff value 8, Cronbach's = 0.90), indicated peer support. Responses to six items, such as "My school is a nice place to be" (range 6–24, cutoff value 12, Cronbach's = 0. 88), were used to determine school support. Being bullied experiences were determined based on responses to four items such as “A particular classmates/friends or group of students pushed, shoved, tripped, or picked fights with me”[21]. The highest education level attained by the parents was used to classify them as (1) junior high school graduate or below, (2) senior high school graduate, or (3) university graduate.
Statistical analysis
An analysis was performed in 2021. The TAALS study team assigned weights to weight variables in order to reduce bias caused by the survey design and differential non-response by individual participants[13]. Missing depressive symptoms records (136/18645 ~ 0.7%) were removed through selection, and no imputation was performed to replace a few missing values for other variables (Additional File 2).
We used the Chi-square tests for categorical variables to analyze the characteristics of participants, depressive symptoms, and substance use by sex and school type.
The logistic regression model was used to assess the association of depressive symptoms and screen use with substance use. Models stratified by sex and school type were employed to determine the associations in each population sub-group. Logistic regression models were mutually adjusted for BMI, skipping breakfast and socio determinants.
SPSS was used to conduct all of the analyses (version 25; IBM SPSS Statistic). To account for multiple testing, an alpha-level of 0.05 was employed throughout the study to test for statistical significance.