Associations of environmental tobacco smoke with ADHD and executive function in early adulthood: results from a cross-sectional study

Background Secondhand smoke (SHS) and thirdhand smoke (THS) have been shown to increase the risk of physical health and mental health. However, the impact of SHS and THS exposure on ADHD symptoms and executive function remain to be elucidated. Methods Online surveys were used to recruit participants at a Chinese vocational college. The frequency of contact with smokers or detecting tobacco odors in residential environments was used to define SHS exposure, whereas the frequency of contact with surfaces contaminated by smokers was used to define THS exposure. The associations of SHS and THS exposure with the risk of ADHD symptoms and the executive function (Behavioral Regulation Index, BRI; Metacognitive Index, MI; Global Executive Composite, GEC) scores were evaluated by logistic regression analysis or linear regression analysis. Results The rate of SHS and THS exposure was 87.7% and 76.9%, with 8.2% stating SHS exposure ≥15 min at least 1 day/week. After adjustment for confounding variables, SHS exposure (≥15 minutes on ≥1 day/week) had higher odds of ADHD symptoms (OR, 1.31; 95% CI, 1.02–1.67), and higher BRI score (β, 2.34; 95% CI, 0.95–3.73), higher MI score (β, 3.12; 95% CI, 1.29–4.95), higher GEC score (β, 5.46; 95% CI, 2.26–8.66). Additionally, the higher the frequency of SHS/THS exposure and the greater the number of surrounding smoker, the higher risk of ADHD symptoms and the poorer executive function ( P trend