Lifestyle Factors Associated with Perceived Stress Among Adolescents: The Indirect Role of Mediterranean Diet Adherence in the Screen Time–Stress Association

Background: Lifestyle habits are critical determinants of psychological health. This study aimed to determine the association between lifestyle factors and perceived stress levels, examining the potential mediating role of Mediterranean diet adherence (MDA). Methods: A cross-sectional study was conducted with 1229 participants (50.04% female, mean age of 13.45 ± 1.97 years). Lifestyle factors, including MDA, screen time (ST), sleep duration, active commuting and physical activity, were assessed. A multiple linear regression and mediation analysis were performed, adjusting for age and sex. Results: Significant sex differences were found, with females reporting higher stress and lower MDA (p < 0.001). Regression models revealed that higher MDA (p = 0.001) and lower ST (b = 0.22, p = 0.014) were significantly related to reduced stress. Mediation analysis showed that MDA statistically (partially) mediated the association between ST and stress (Indirect effect = 0.025, 95%CI; 0.005, 0.054). Specifically, MDA accounted for 10.12% of the total effect of ST on stress, representing a modest indirect contribution. Conclusions: Elevated ST routines are positively associated with adolescent perceived stress, whereas higher MDA displays an inverse relationship with stress. Additionally, this association is structurally modulated by MDA, highlighting that the unfavorable correlates of excessive television viewing and video-game use are modestly linked to concurrent variations in dietary quality within school environments. Given the cross-sectional design, these findings should be interpreted as indirect associations rather than causal pathways, and reverse or bidirectional relationships cannot be ruled out.