Demographics information of the Healthy Brain Network sample.

Final analysis tree illustrating all included analytical specifications.

Each node represents a distinct analytical parameter in the multiverse analysis. Note that due to space limitations, not all parameter nodes are displayed in this visualization. Information on comorbid diagnoses and medication status was available only in the HBN sample, and these factors were therefore investigated exclusively in this dataset. HC = Healthy Control, IAF = Individual Alpha Frequency.

Overview of sample characteristics and variable distributions.

Density plots show the distribution of (A) age, (B) IQ, (C) IAF, (D-F) and SWAN scores (Inattention, Hyperactivity, and Total) across the three groups. (G-I) Scatter plots display the relationship between (G) IAF and age, (H) between TBR and age, (I) and TBR and IAF across all participants. The regression line is shown with standard error bands. Note. IAF = Individual Alpha Frequency. TBR = Theta Beta Ratio. HC = Healthy Control.

Neurophysiological data from the Healthy Brain Network sample.

(A) Scalp topographies, (B) power spectra and (C) aperiodic signal for HC, ADHD-Combined, and ADHD-Inattentive groups. The figure displays aperiodic-adjusted power during EO condition, computed using a canonical frequency range (theta: 4-8 Hz; beta: 13-30 Hz) and TBR. Electrodes highlighted on the topographies correspond to the six regions of interest derived from literature used across different branches of multiverse analysis. The power spectra and aperiodic signal were computed by averaging across all electrodes within each respective region of interest. Note. TBR = theta-beta ratio. HC = healthy controls. Comb = Combined. In = Inattentive.

Results of the multiverse analysis in the HBN sample showing the proportion of significant effects across 576 universes.

Specification curve representing all universes for the healthy control ADHD-Inattentive contrast.

The top panel shows regression estimates for each specification, sorted by regression estimate, with 95% confidence intervals. Statistically significant positive estimates are shown in green, negative estimates in red, and non-significant estimates in gray. The bottom panel indicates which analytical choices were associated with significantly positive (i.e., higher TBR for ADHD compared to HC) or negative (i.e., lower TBR for ADHD compared to HC) effects across specifications. Note. CI = confidence interval. f = female. EC = eyes closed. EO = eyes open. AVG = average reference. LM = linked mastoid reference. canonical = canonical frequency range. relative to IAF = bandwidth relative to individual alpha frequency.

Possibility space of regression estimates from the subset of analytical choices yielding the highest number of significant results.

(A) ADHD-Inattentive * IAF interaction: Significant effects (46 significant out of 48 possibilities) were predominantly observed when using frequency bands relative to IAF, the aperiodic signal, and including children with comorbid diagnoses. (B) ADHD-Inattentive * Age * IAF interaction: This positive effect emerged almost exclusively when TBR was computed using canonical frequency bands, aperiodic-adjusted power, and analyses included participants with comorbidities (37 out of 48 significant). (C) ADHD-Inattentive * Gender * IAF interaction: The effect was found exclusively under frequency bands relative to IAF, primarily in the aperiodic signal, and when children with comorbid diagnoses were included (28 out of 48 significant). Note. The significant estimates are highlighted in red and non-significant in grey.

Specification curve representing all universes for the healthy control ADHD-Combined contrast.

The top panel shows regression estimates for each specification, sorted by regression estimate, with 95% confidence intervals. Statistically significant positive estimates are shown in green, negative estimates in red, and non-significant estimates in gray. The bottom panel indicates which analytical choices were associated with significantly positive (i.e., higher TBR for ADHD compared to HC) or negative (i.e., lower TBR for ADHD compared to HC) effects across specifications. Note. CI = confidence interval. f = female. EC = eyes closed. EO = eyes open. AVG = average reference. LM = linked mastoid reference. canonical = canonical frequency range. relative to IAF = bandwidth relative to individual alpha frequency.

Possibility space of regression estimates from the subset of analytical choices yielding the highest number of significant results in the ADHD-Combined vs. healthy control comparisons.

(A) ADHD-Combined * Age interaction: Significant effects (24 out of 96) were primarily observed when using frequency bands relative to IAF and the aperiodic signal. (B) ADHD-Combined * IAF interaction: A negative effect emerged almost exclusively under frequency bands relative to IAF, predominantly in the aperiodic signal, and in analyses excluding children on medication (47 out of 48 significant). (C) ADHD-Combined * Gender interaction: This positive effect appeared almost exclusively in the EC condition, with frequency bands relative to IAF and 1/f-uncorrected power (27 out of 48 significant). (D) ADHD-Combined * Age * Gender, (E) ADHD-Combined * Gender * IAF and (F) ADHD-Combined * Age * Gender * IAF interactions: These effects appeared mainly in the EC condition, almost exclusively when comorbidities were included and medication excluded (26, 35 and 31 out of 72 significant, respectively). Note. Significant estimates are highlighted in red and non-significant estimates are shown in grey.