Sleep-like slow waves in ADHD: Regional specificity in combined type.
Gong S, Lu X, Wang H, Wang Y • International journal of psychophysiology : official journal of the International Organization of Psychophysiology • 2026
Sleep-like slow wave activity during wakefulness was significantly elevated in both ADHD subtypes compared to healthy controls, with topographic analysis revealing that local frontal lobe abnormalities specifically distinguished ADHD-C from ADHD-I, and prefrontal SWA features were selectively associated with executive control and orientation deficits only in the combined type.
Key Findings
Results
Sleep-like slow wave activity (SWA) during wakefulness was present in all groups during task participation but was significantly elevated in both ADHD subtypes compared to healthy controls.
The study included 120 children divided into healthy controls (HC), inattentive-type (ADHD-I), and combined-type (ADHD-C) groups.
EEG recordings were collected during the Attention Network Test (ANT).
SWA was detected in all participants, indicating this phenomenon is not exclusive to ADHD.
Both ADHD subtypes showed elevated SWA compared to typical development.
Results
ADHD combined-type showed the most pronounced SWA abnormalities, with increased maximum negative peak amplitude, prolonged duration, and steeper slow wave slope.
Three specific SWA parameters were quantified: maximum negative peak amplitude, duration, and slow wave slope.
All three parameters were most abnormal in ADHD-C compared to both ADHD-I and HC.
The steeper slope in ADHD-C suggests more abrupt cortical downstates during wakefulness.
These global SWA parameters were sufficient to distinguish ADHD from typical development.
Results
Topographic analysis revealed that local frontal lobe SWA abnormalities specifically distinguished ADHD-C from ADHD-I, whereas global SWA parameters could not make this distinction.
Global SWA parameters distinguished ADHD (both subtypes) from healthy controls but could not differentiate between the two ADHD subtypes.
Only topographic (regional) analysis identified frontal lobe abnormalities unique to ADHD-C.
This finding highlights the importance of spatial/regional EEG analysis over global measures for subtype differentiation.
The frontal lobe specificity aligns with known frontal executive function deficits in combined-type ADHD.
Results
Prefrontal region SWA features were selectively associated with executive control and orientation deficits in ADHD-C but not in ADHD-I.
The Attention Network Test (ANT) was used to measure executive control and orientation network performance.
Correlations between prefrontal SWA and behavioral performance were subtype-specific.
No significant association between prefrontal SWA and behavioral deficits was found in the ADHD-I group.
This selective association suggests distinct neurophysiological underpinnings for the two ADHD subtypes.
Results
Moderation analyses demonstrated that ADHD subtype significantly modulated the relationship between SWA and behavioral performance.
Moderation analyses were conducted to assess whether the SWA-behavior relationship differed by ADHD subtype.
ADHD subtype was a significant moderator of the SWA–behavioral performance relationship.
This finding indicates that the functional significance of SWA is not uniform across ADHD subtypes.
Results support the utility of SWA as a subtype-specific neurophysiological marker rather than a general ADHD marker.
Conclusions
The study proposed that sleep-like slow wave dynamics during wakefulness reflect underlying differences in attentional processing between ADHD subtypes and could inform neurophysiological stratification.
SWA during wakefulness is conceptually linked to local sleep intrusion into conscious states, potentially impairing cognitive processing.
The authors suggest these findings could inform 'future efforts toward neurophysiological stratification and targeted intervention.'
The lack of objective neurophysiological markers was identified as a key challenge motivating this research.
SWA was framed as a candidate subtype-specific neural marker for ADHD diagnosis.
What This Means
This research suggests that brief episodes of brain activity resembling sleep — called slow waves — occur in the brains of children with ADHD even while they are awake and trying to pay attention. Using EEG (brainwave recordings) during a computer-based attention task, researchers studied 120 children: those with no diagnosis, those with the inattentive type of ADHD, and those with the combined type (both inattentive and hyperactive). They found that these 'sleep-like' brain waves were present in all children but were stronger and more intense in children with ADHD, especially those with the combined type, who showed larger, longer, and sharper slow waves.
Importantly, the location of these abnormal brain waves mattered. When researchers looked at the brain as a whole, they could tell ADHD apart from typical development, but they could not tell the two ADHD types apart. However, when they looked specifically at the frontal part of the brain — an area involved in planning, impulse control, and attention — they found abnormalities that were unique to the combined type of ADHD. Slow wave activity in this frontal region was also linked to poorer performance on tasks measuring executive control and the ability to orient attention, but only in children with the combined type, not the inattentive type.
This research suggests that these waking slow waves could serve as a measurable brain-based marker to help distinguish between ADHD subtypes, which is currently difficult to do objectively. This could potentially help clinicians better categorize children with ADHD and eventually tailor treatments more precisely to the specific brain patterns underlying each subtype.
Gong S, Lu X, Wang H, Wang Y. (2026). Sleep-like slow waves in ADHD: Regional specificity in combined type.. International journal of psychophysiology : official journal of the International Organization of Psychophysiology. https://doi.org/10.1016/j.ijpsycho.2026.113349