New Finding Links ADHD to Increased Risk of Dementia

Researchers have found that adults with ADHD have elevated levels of iron in a specific region of the brain, which may be linked to neuronal damage. This accumulation of iron has been linked to neurodegenerative diseases such as Alzheimer’s, suggesting that adult ADHD may increase the risk of dementia later in life. More studies are needed to better understand this link.

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition characterized by difficulty sustaining attention, impulsivity, and hyperactivity.

The development of ADHD is influenced by a complex interplay of genetic and environmental factors. There is no single test to diagnose ADHD, and the diagnosis can be made in both youth and adults based on the presence of the characteristic behavioral syndrome.

Adult ADHD is often associated with an increased prevalence of cardiovascular risk factors, such as smoking, obesity, diabetes, and altered lipid profiles, all of which are well-established risk factors for age-related cognitive decline.

Although it is often diagnosed in childhood, it can persist into adulthood. Recent studies suggest that adults with ADHD may have a higher risk of developing dementia and Alzheimer's disease later in life, but the reasons for this association are not yet fully understood.

One hypothesis for this link involves the accumulation of iron in the brain. Iron is essential for several brain functions, but excess iron can be harmful, contributing to brain aging and neurodegenerative diseases such as Alzheimer's and Parkinson's.

Previous studies have shown that brain iron tends to increase with age and can affect cognition. However, little is known about how it behaves in adults with ADHD. To investigate this question, researchers analyzed the brains of 32 adults with ADHD and 29 healthy adults (control group) using a specialized MRI scan called quantitative susceptibility mapping (QSM).

This technique allows the amount of iron present in different brain regions to be measured. In addition, researchers from the University of Geneva (UniGE), Geneva, evaluated the levels of a protein called neurofilament light chain (NfL) in the blood.

This protein is a biomarker of neuronal damage and can indicate whether there is any degeneration in the nervous system. Elevated levels of NfL have been observed in people with Alzheimer's and other neurodegenerative diseases.

Participants also underwent standardized tests to assess their cognitive function and were assessed for lifestyle factors such as smoking, obesity and diabetes, which are known to affect dementia risk.

The results showed that adults with ADHD had higher iron levels in the right precentral cortex, a region of the brain involved in motor control and attention regulation. This difference was statistically significant when compared to healthy participants.

In addition, the researchers observed that the higher the amount of iron in this region of the brain, the higher the levels of the protein NfL in the blood, suggesting possible neuronal damage associated with excess iron.

These findings suggest that adults with ADHD may have altered iron distribution in the brain, which may be related to neuroaxonal damage (injury to neurons).

Since iron accumulation has been linked to the development of diseases such as Alzheimer's and Parkinson's, these results raise the possibility that adult ADHD may increase the risk of neurodegenerative problems later in life.

The researchers note that this study had a relatively small number of participants and that more research is needed to confirm these findings.

Future studies should investigate whether these brain changes observed in adults with ADHD are directly linked to an increased risk of dementia and whether medical interventions or lifestyle changes can reduce this risk.

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Brain iron load and neuroaxonal vulnerability in adult attention-deficit hyperactivity disorder

Jatta Berberat, Sonja M Kagerer, Claudia Späni,  Jun Hua, Francesco Bavato, Philipp Gruber, Peter CM van Zijl, Nader Perroud, Xu Li, Philipp Stämpfli, Erich Seifritz, Karl-Olof Lövblad, Boris B Quednow, and Paul G Unschuld

Psychiatry and Clinical Neurosciences. 27 February 2025

https://doi.org/10.1111/pcn.13806

Abstract: 

Adult attention deficit hyperactivity disorder (ADHD) may be associated with an increased risk of dementia in old age. Here, we investigated the liability for neurodegenerative brain disease in adult ADHD, possibly reflected by increased brain iron content and associated neuroaxonal vulnerability.

Thirty-two adults with ADHD (35 ± 10 years) and 29 age- and sex-matched controls (32 ± 12 years) underwent magnetic resonance imaging (MRI), standardized psychometric testing and assessment of lifestyle factors. Quantitative susceptibility mapping (QSM) was used to assess magnetic abnormalities indicating local alterations of iron deposition in the brain. By calculating QSM-maps, local iron deposition was tested for statistically significant differences between ADHD and healthy controls. Plasma neurofilament light chain (NfL) levels were measured as an indicator of neuroaxonal integrity by using a fourth-generation ELLA immunoassay.

Brain iron content differed in persons with ADHD, with strongest effects observable in the right precentral cortex (healthy controls: 0.0033 ± 0.0017ppm; ADHD: 0.0048 ± 0.0016ppm; t(59) = 3.56, P < 0.001). Moreover, right precentral cortex iron in persons with ADHD was associated with increased blood NfL levels (F(1.57) = 13.2, P = 0.001, r2 = 0.19). Our results indicate altered regional iron content in the brains of adults with ADHD. The observed association between increased precentral magnetic susceptibility and increased NfL suggests a connection between local excess of brain iron and neuroaxonal damage in ADHD. Given the limited sample size of the current study and the naturalistic medication plan, further longitudinal studies are needed to establish whether altered brain iron distribution in adults with ADHD may be associated with an increased risk of dementia at old age.