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

## TL;DR

This study found that exposure to secondhand and thirdhand smoke is linked to ADHD symptoms and worse executive function in young adults.

## Contribution

The study is among the first to explore the association between SHS/THS exposure and ADHD/executive function in early adulthood.

## Key findings

- SHS exposure was associated with higher odds of ADHD symptoms and worse executive function scores.
- Higher frequency of SHS/THS exposure correlated with increased ADHD risk and poorer executive function.
- Adjustment for confounders confirmed significant associations between SHS exposure and ADHD/executive function.

## Abstract

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.

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.

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 <0.001).

SHS and THS exposure were related to the occurrence of ADHD symptoms and impaired executive function among young adults at a Chinese vocational college in this cross-sectional study. Further researches are warranted to validate these associations in more diverse populations.