The dynamic interplay between loneliness and health behaviors from adolescence to midlife: A Norwegian population-based cohort study

BACKGROUND: Adverse health behaviors, such as physical inactivity and smoking, constitute a potential pathway connecting loneliness to poor mental and physical health. No prior study has investigated the dynamic interplay between loneliness and a broad range of health behaviors across the first half of life. METHODS: = 3,072) spanning 28 years from adolescence to midlife. Applying a propensity score-based causal inference approach, we examined bidirectional prospective associations between loneliness and health behaviors, comprising alcohol use, body mass index (BMI), smoking, and physical exercise. RESULTS: Loneliness in adolescence was associated with lowered physical exercise (mean difference: -14.13 minutes/week, 95% CI: -26.54 to -1.72), and loneliness during young adulthood was linked to increased BMI (0.37 points, 0.12-0.63). In the reverse direction, moderate alcohol use (-0.07 SD, -0.13 to -0.01 and - 0.19 SD, -0.33 to -0.05), smoking (-0.12 SD, -0.23 to -0.01), and moderate physical exercise (-0.16 SD, -0.26 to -0.07 and - 0.07 SD, -0.14 to -0.01) during adolescence and emerging adulthood were linked to reduced loneliness. All other associations were consistent with a null effect. CONCLUSIONS: Our results provide limited support for the causal effects of loneliness on health behaviors across the first half of life. By contrast, findings in the reverse direction suggest that health behaviors in young people - whether health-promoting or risky - are socially embedded and may facilitate socializing. To tackle youth loneliness, public health policies should promote equitable access to health-promoting behaviors.