A new study published in the Journal of emotional disorders noted that adults with attention / hyperactivity deficit disorder (ADHD) have signs of dysfunction of the glymphatic system, which can be linked to their cognitive difficulties. The results suggest that disturbances in the brain waste release system could help explain part of the persistent memory and attention problems observed in adults with the condition.
ADHD is a common neurodevelopmental disorder marked by symptoms of inattention, impulsiveness and hyperactivity. Although it is often diagnosed in childhood, many people continue to feel good symptoms in adulthood. In adults, ADHD can interfere with work, relationships and daily functioning, and is often accompanied by cognitive problems such as forgetting and difficulty supporting concentration. Although behavioral symptoms are widely studied, the biological mechanisms underlying adult ADHD are less understood.
An area of growing interest among scientists is the glymphatic system – a network that helps clean brain waste. This system works mainly during deep sleep and uses cerebrospinal fluid to eliminate harmful substances. Glymphatic function problems have been linked to other brain disorders, such as Alzheimer’s disease. However, little is known about its role in ADHD, especially in adults. The researchers behind this study wanted to explore whether changes in glymphatic function could help explain the cognitive deficiencies associated with the condition.
To do this, the team analyzed brain imaging and cognitive data from 41 adults diagnosed with ADHD and compared them to 108 healthy adults. The data come from the University of California of Los Angeles Consortium for the study of neuropsychiatric phenomic the 5C and included structural and functional magnetic resonance imaging (MRI), as well as the results of several cognitive tests. The researchers used advanced neuroimagery techniques to assess three indicators of the glymphatic function: the volume of the choroid plexus (part of the brain which produces cerebrospinal fluid), a measure known as the alps index (which reflects the way the fluid moves along the blood vessels in the brain), and the resistance of the connection between brain activity and brain activity and The flow of the brain fluid (the Gbold-CSF flow).
Participants also completed a range of assessments, including the adult ADHD self-assessment scale to measure the symptoms of ADHD and standardized tests to assess memory, attention and verbal learning. These included the Verbal learning test of California and the Wechsler memory scale.
The results have shown that adults with ADHD have lower alps index scores than healthy individuals, suggesting reduced glymphatic activity. This difference was observed in the two hemispheres of the brain. The decrease in alps scores was linked to a reduction in the movement of fluids along the specific fiber pathways in the brain, in particular those involved in communication between regions. These results indicate a possible alteration of the effectiveness of the brain able to clean waste.
Although the volume of the choroid plexus tended to be higher in the TDAH group, this difference did not reach statistical meaning. This may suggest a potential compensatory response or a marker of the altered cerebrospinal fluid, but more research is necessary to draw firm conclusions. Similarly, there were no significant differences between ADHD and the control groups in terms of GBOLD-CSF coupling, which reflects functional synchronization between brain activity and flow of fluid. This suggests that if structural glymphatic changes can be present, the overall coordination between brain activity and fluid remains intact in adults with ADHD.
Above all, the researchers found that the lower alps index scores were associated with less performance on memory tasks, including visual reproduction and delayed recognition. These correlations were stronger in the right hemisphere. The ALPS index has also shown links with higher scores on obsessive compulsive symptoms in ADHD participants, suggesting a broader relationship between glymphatic function and psychiatric characteristics.
In healthy participants, higher ALPS scores were also associated with better memory performance, which suggests that glymphatic activity can play a wider role in supporting cognitive health between individuals, not just those with ADHD.
These results open up the possibility that glymphatic dysfunction contributes to cognitive symptoms felt by adults with ADHD. Researchers propose that altered waste could lead to the accumulation of metabolic by-products that interfere with brain signaling, in particular in the ways involving dopamine and norepinephrine. These neurotransmitters are already known to play a role in the attention, motivation and treatment of rewards – all areas often affected in ADHD.
Another possible explanation is that the altered glymphatic function can contribute to low grade inflammation in the brain, which has been more and more recognized in ADHD research. Inflammation can disrupt brain development and affect how neurons communicate. Researchers also point out that sleep problems, which are common in ADHD, can worsen glymphatic dysfunction, as this system works most effectively during deep sleep.
At the cellular level, the authors suggest that astrocytes – appropriate brain cells that help regulate the glymphatic system – can play an important role. Astrocytes help manage the flow of fluids through the channels called aquaporins and also influence the development of cerebral circuits. The malfunction of these cells could create a cascade of problems affecting both waste clearance and neuronal communication.
Although this study is one of the first to examine the glymphatic function in adult ADHD, it has several limits. Because the data is transversal, researchers cannot determine whether glymphatic dysfunction causes cognitive problems or results. Longitudinal studies are necessary to better understand the direction of this relationship. The relatively small size of the sample also limits the generalization of the results, and future research should aim to reproduce these results in larger and more diverse groups.
Despite these limits, the study adds an important part to the ADHD puzzle. He suggests that biological systems beyond the signaling of neurotransmitters, such as waste clearance-perhaps play a significant role in the development and persistence of the disorder. These ideas could possibly lead to new therapeutic strategies. For example, improving the quality of sleep, promoting regular physical activity or reducing brain inflammation could support glymphatic function and potentially facilitate cognitive symptoms in adults with ADHD.
The study, “Dysfunction of the glymphatic system in adult ADHD: relationship to cognitive performance”, was written by Yan Fang, Juan Peng, Tiantian Chu, Feng Gao, Fei Xiong and Ye Tu.
