IMPORTANCE Information about longitudinal associations of attention-deficit/hyperactivity disorder (ADHD) diagnosis, symptom severity, pharmacotherapy, and incident nicotine and tobacco use, including e-cigarettes, among US youths is limited.

OBJECTIVE To evaluate whether ADHD diagnosis, symptom severity, and pharmacotherapy are associated with incident e-cigarette and tobacco use over a 9-year period.

DESIGN, SETTING, AND PARTICIPANTS This longitudinal cohort study followed up a nationally representative sample of US youths and their parents in the Population Assessment of Tobacco and Study via questionnaires from wave 1 (September 2013 to December 2014) to waves 2 to 7 (October 2014 to April 2023). Participants were representative of the US civilian noninstitutionalized population. Youths aged 12 to 17 years at wave 1 (N = 13 572) and their parents were interviewed.

EXPOSURES Time in years and history of ADHD diagnosis, symptom severity, and pharmacotherapy at wave 1 were used to construct 9 mutually exclusive subgroups of US youths, including those with ADHD diagnosis and pharmacotherapy, ADHD diagnosis without pharmacotherapy, and population controls without ADHD diagnosis; within each of these 3 subgroups, ADHD symptom severity was categorized as none, 1 to 2, or 3 to 4 symptoms.

MAIN OUTCOMES AND MEASURES Incident e-cigarette use, cigarette smoking, other tobacco use, and dual use (e-cigarette and cigarette and/or other tobacco use) in weighted percentages with 95% CIs.

RESULTS Of the 13 572 youths included in the analysis, 6967 (51.3%; 95% CI, 51.2%-51.5%) were male. An estimated 1881 participants (14.1%; 95% CI, 13.2%-15.0%) were diagnosed with ADHD. Multivariable logistic regression analyses indicated that the adjusted odds of incident e-cigarette use, cigarette smoking, other tobacco use, and dual use did not significantly differ between those with asymptomatic ADHD (with or without pharmacotherapy) compared with population controls. In contrast, all subgroups who had 3 or more ADHD symptoms (with or without pharmacotherapy) had significantly higher adjusted odds of e-cigarette use (adjusted odds ratio [AOR], 1.60; 95% CI, 1.34-2.04), cigarette smoking (AOR, 1.52; 95% CI, 1.22-1.89), other tobacco use (AOR, 1.61; 95% CI, 1.27-2.02), and dual use (AOR, 1.72; 95% CI, 1.38-2.14) compared with youths with asymptomatic ADHD or population controls. Among youths with ADHD, those with highly symptomatic ADHD were significantly more likely to initiate e-cigarette (AOR, 1.68; 95% CI, 1.16-2.44) and dual use (AOR, 1.82; 95% CI, 1.17-2.83) than youths without symptoms.

CONCLUSIONS AND RELEVANCE In this cohort study of US youths, ADHD symptoms were associated with the onset of nicotine and tobacco use. Findings highlight the importance of early diagnosis and effective treatment of ADHD to alleviate symptoms and reduce the risk of later nicotine and tobacco use.