Resting low-frequency EEG correlates of adult ADHD trait symptoms beyond internalizing symptoms in young adults.

INTRODUCTION: Intrinsic EEG oscillations provide a non-invasive window into arousal- and attention-related individual differences, but resting low-frequency EEG correlates of adult attention-deficit/hyperactivity disorder (ADHD) trait symptoms remain incompletely characterized in non-clinical young adults. METHODS: We analyzed eyes-closed resting-state EEG from a cohort of 337 Chinese undergraduates with usable EEG data; the primary analysis included 334 participants. ADHD trait symptoms were assessed dimensionally with a 26-item adult ADHD self-report scale. The prespecified EEG family comprised log posterior-occipital delta power, log posterior delta power, log global delta power, and frontocentral log theta/beta ratio. The primary HC3 regression adjusted for age, sex, trait anxiety, depressive symptoms, and Beck Anxiety Inventory total score, with false-discovery-rate correction across the planned EEG family. RESULTS: Higher ADHD trait symptoms were associated with lower posterior-occipital delta power [β = 0.114, 95% CI (0.199, 0.029), p = 0.008]. Posterior delta, global delta, and frontocentral theta/beta ratio showed convergent negative associations after false-discovery-rate correction. The posterior-occipital delta association remained negative and statistically significant across extended covariate models and robustness analyses. Across 64 reasonable covariate specifications, all coefficients were negative and 65.6% reached p < 0.05. DISCUSSION: Adult ADHD trait symptoms were modestly associated with lower posterior-occipital and broader low-frequency resting EEG power after accounting for internalizing symptoms. The findings support a stable group-level dimensional association within this sample, but not individual-level screening, diagnostic support, risk classification, or causal inference.