Data for this cross-sectional study were drawn from the Youth Risk Behavior Surveillance System (YRBSS) between 2013 and 2019. The YRBSS is a publicly accessible database that was developed in 1990 by the Centers for Disease Control and Prevention (CDC) to monitor health risk behaviors established in childhood and early adolescence that are associated with death, disability, and social problems among youth and adults in the United States (available at: https://www.cdc.gov/healthyyouth/data/yrbs/overview.htm). The YRBSS uses a three-stage cluster sampling design with a target population of students in grades 9 through 12, and these surveys are conducted every two years. A self-administered computer-scanned questionnaire was used for the survey that was anonymous and voluntary and had parental permission. The protocol of YRBSS were approved by the institutional review board of the CDC and is publicly available. Participants aged 14-18 years old with complete information on suicide behaviors, digital device use, self-perceived weight, and body mass index (BMI) were included. Participants with missing information on important covariates, such as physical activity, drinking alcohol, cyber bullying, and school bullying, were excluded.

The outcome of this study was the suicidality of adolescents. Suicidality includes considered suicide, made a suicide plan, attempted suicide, and injurious suicide attempt. Adolescents were considered to have suicidality if they had any of these four suicidalities. Suicidality was measured through the YRBSS questionnaire (https://yrbs-explorer.services.cdc.gov/#/). The type of “considered suicide” was measured by the survey question, “During the past 12 months, did you ever seriously consider attempting suicide?”. The type of “made a suicide plan” was measured by the survey question, “During the past 12 months, did you make a plan about how you would attempt suicide?”. The type of “attempted suicide” was measured by the survey question, “During the past 12 months, how many times did you actually attempt suicide?”. The type of “injurious suicide attempt” was measured by the survey question, “If you attempted suicide during the past 12 months, did any attempt result in an injury, poisoning, or overdose that had to be treated by a doctor or nurse?”.

The characteristics of participants were collected including age (≤16 years and >16 years), sex (female and male), race (Hispanic/Latino and others), BMI, screen time (<3h and ≥3h), self-perceived overweight (yes and no), smoking (yes and no), drinking alcohol (yes and no), physical activity (yes and no), illegal drug (yes and no), cyber bullying (yes and no), school bullying (yes and no), school safety concern (yes and on), early sexual intercourse (yes and no), and sadness or hopeless (yes and no).

Weighting factors from the YRBSS database (PSU, Stratum, Weight) were applied to each student’s record to adjust for non-response and the oversampling of black and Hispanic students in the sample. The statistical description was performed based on the study outcomes of suicidality, considered suicide, made a suicide plan, attempted suicide, and injurious suicide attempt. Weighted prevalence rates of suicidality, considered suicide, made a suicide plan, attempted suicide, and injurious suicide attempt were reported. Weighted chi-squared test was used to analyze the differences in prevalence rates of suicidality, considered suicide, made a suicide plan, attempted suicide, and injurious suicide attempt by different characteristics. Multivariable logistic regression model was used to investigate the associations between screen time, overweight/obesity, self-perceived overweight, and suicidality, and the results were expressed as odds ratio (OR) and 95% confidence interval (CI). In analyzing the associations between screen time and overweight/obesity and self-perceived overweight, the logistic regression model was adjusted for sex, race, smoking, school bullying, and sadness or hopeless. In analyzing the associations of overweight/obesity, self-perceived, and screen time with suicidality, the logistic regression model was adjusted for sex, race, smoking, drinking alcohol, illegal drug, cyber bullying, school bullying, school safety concern, early sexual intercourse, and sadness or hopeless.

The mediation of the association between screen time and suicidality by overweight/obesity and self-perceived overweight was assessed using the “RMediation” and “jtools” packages in R software (23). The relationship of screen time with overweight/obesity and self-perceived overweight was represented by “Effect A”. The relationship of overweight/obesity and self-perceived overweight with suicidality was represented by “Effect B”. The indirect effect was “Effect A × Effect B”. The relationship between screen time and suicidality was represented by “Effect C” (total effect). Moreover, the relationship between screen time and suicidality was represented by “(Effect C’)” (direct effect) after adjusting for overweight/obesity or self-perceived overweight. Standardized coefficients were utilized to show the estimates for each pathway. The percentage of mediation effect was calculated as: [exp(Effect C) - exp(Effect A)] ×100/[exp(Effect C)-1].

All statistical analyses were performed by R 4.2.0 software (Institute for Statistics and Mathematics, Vienna, Austria). P-values (two-sided) less than 0.05 was considered statistically significant.

The total number of participants in the YRBSS surveys of 2013, 2015, 2017, and 2019 was 57,649. A total of 26,918 participants were excluded, including 568 participants aged <14 years, 14,530 participants with missing information on suicidality, 1,750 participants with missing information on screen time, 3,470 participants with missing information on overweight/obesity and self-perceived overweight, and 6,600 participants with missing important covariates. A total of 30,731 adolescents were included in the analysis ( Figure 1 ). Of these 30,731 adolescents, 6,350 (20.65%) had suicidality, including 5,361 (17.45%) with considered suicide, 4,432 (14.42%) with made a suicide plan, 2,300 (7.45%) with attempted suicide, and 677 (2.21%) with injurious suicide attempt ( Table 1 ). There were 13,579 (43.75%) adolescents with screen time ≥3h, 9,379 (38.45%) adolescents with overweight/obesity, and 10,000 (38.35%) adolescents with self-perceived overweight.

Table 2 presents the relationships between screen time, overweight/obesity, self-perceived overweight, and suicidality. Adolescents with screen time ≥3h were related to higher odds of overweight/obesity (OR=1.27, 95%CI: 1.19-1.38) and self-perceived overweight (OR=1.38, 95%CI: 1.30-1.48) after adjusting for sex, race, smoking, school bullying, and sadness or hopeless. Adolescents with overweight/obesity (OR=1.30, 95%CI: 1.19-1.43) and self-perceived overweight (OR=1.54, 95%CI: 1.39-1.70) were associated with higher odds of suicidality after adjusting for sex, race, smoking, drinking alcohol, illegal drug, cyber bullying, school bullying, school safety concern, early sexual intercourse, and sadness or hopeless. Moreover, adolescents with screen time ≥3h were related to higher odds of suicidality after adjusting confounders (OR=1.35, 95%CI: 1.23-1.46). When further adjusted for overweight/obesity (OR=1.32, 95%CI: 1.22-1.455) or self-perceived overweight (OR=1.31, 95%CI: 1.20-1.43), adolescents with screen time ≥3h were still associated with higher odds of suicidality. Specific suicidality, including considered suicide, made a suicide plan, and attempted suicide, also supported the above results except for injurious suicide attempt (all P<0.05) ( Table 2 ).

Table 3 and Figure 2 report the mediating effects of overweight/obesity and self-perceived overweight on the association between screen time and suicidality. In the analysis of the mediating effects between screen time, overweight/obesity, and suicidality, the direct effect was 0.28 (0.20, 0.37), the mediating effect was 0.06 (0.03, 0.09), and 4.67% of the association between screen time and suicidality was mediated by overweight/obesity. In the specific analysis of suicidality, the mediating effect of overweight/obesity was 0.07 (0.04, 0.10) and mediated 5.61% of the association between screen time and considered suicide, 0.06 (0.03, 0.09) and mediated 5.87% of the association between screen time and made a suicide plan, and 0.05 (0.01, 0.09) and mediated 4.57% of the association between screen time and attempted suicide, while no statistically significant association was found between screen time and injurious suicide attempt. In the analysis of the mediating effects between screen time, self-perceived overweight, and suicidality, the direct effect was 0.27 (0.18, 0.36), the mediating effect was 0.14 (0.10, 0.17), and 9.66% of the association between screen time and suicidality was mediated by self-perceived overweight. In the specific analysis of suicidality, the mediating effect of self-perceived overweight was 0.14 (0.11, 0.18) and mediated 10.79% of the association between screen time and considered suicide, 0.12 (0.09, 0.15) and mediated 11.57% of the association between screen time and made a suicide plan, and 0.12 (0.07, 0.16) and mediated 9.96% the association between screen time and attempted suicide. No statistically significant association was found between screen time and injurious suicide attempt (P>0.05).

Table 4 and Figure 3 present the mediating effects of overweight/obesity and self-perceived overweight on the association between screen time and suicidality based on sex. In the analysis of the mediating effect of overweight/obesity, 7.74% of the association between screen time and suicidality in females was mediated by overweight/obesity, whereas no mediating effect of overweight/obesity was found in males. In females, the proportion of mediating effects of overweight/obesity was 9.17%, 11.8%, and 4.52% for considered suicide, made a suicide plan, and attempted suicide, respectively. In the analysis of the mediating effect of self-perceived overweight, self-perceived overweight mediated the association between screen time and suicidality at 10.33% in females and 8.4% in males. In females, the proportion of mediating effects of self-perceived overweight was 11.87%, 18.04%, and 10.89% for considered suicide, made a suicide plan, and attempted suicide, respectively. In males, the proportion of mediating effects of self-perceived overweight was 9.00% and 6.22% for considered suicide and made a suicide plan, respectively. No association was found between screen time and injurious suicide attempt was found in females, nor between screen time and attempted suicide and injurious suicide attempt in males.