Introduction: Over 1 billion smokers worldwide, one-third of whom have mental and behavioral disorders, exist. However, factors influencing mental and behavioral disorders due to use of tobacco remain unexplored. We aim to investigate the relationship between dietary iron intake and mental and behavioral disorders due to use of tobacco. Methods: Using large population cohort data from the UK Biobank, we employed logistic and Cox regression to explore the cross-sectional and longitudinal associations between dietary iron intake and mental and behavioral disorders due to use of tobacco. Additionally, we assessed the nonlinear relationship between dietary iron intake and mental and behavioral disorders due to use of tobacco using restricted cubic spline plots. Results: The cross-sectional analysis included 50,991 participants. The logistic regression results indicated that dietary iron intake was negatively associated with mental and behavioral disorders due to use of tobacco. A total of 50,921 participants were included in the cohort study. The Cox regression results supported the protective effect of increased dietary iron intake against mental and behavioral disorders due to use of tobacco. The stratified and sensitivity analysis results were consistent with the main results. The restricted cubic spline plots showed a nonlinear relationship between dietary iron intake and mental and behavioral disorders due to use of tobacco. The risk reduction rate initially accelerated and then slowed in the total sample, the two age, and the male groups. In contrast, it declined rapidly at first and then leveled off in the female group. Conclusion: This study found that dietary iron intake has a protective effect against mental and behavioral disorders due to use of tobacco, revealing a nonlinear association between the two. These findings offer valuable insights for the prevention and treatment of mental and behavioral disorders due to use of tobacco in the future.
