A new study by the American Neurological Association has found that the condition can lead to neurodegenerative diseases like Alzheimer’s, Parkinson’s, and even Alzheimer’s disease.
A review of more than 300 published studies published between 1970 and 2015 found that at least one out of three patients with ADHD have symptoms of neurodegenesis, and some researchers are now beginning to suggest that the link may be genetic.
The first such study, published in the Journal of the American Academy of Neurology (JAAO), compared a group of ADHD patients and healthy controls in which some of the patients also had some form of neuropsychiatric disorders.
The results showed that the children of ADHD had significantly higher rates of neurogenesis in the brains of their unaffected siblings.
That finding has led some researchers to speculate that ADHD may be a result of genes that are related to neurogenes.
The JAAO review also found that ADHD was associated with a lower IQ and higher risk of cardiovascular disease, stroke, and other forms of cardiovascular diseases, including heart failure.
The study was the first to look at the neurogenetic basis for the ADHD-linked neurodegens, and it was published in Neurology.
“We believe the link between neurogenetics and ADHD is genetic,” lead author and JAAA director of neurology James H. Wigley told Ars.
“The relationship is not the result of environmental influences.
The relationship is genetic.”
Wigly and his colleagues conducted the study using data from more than 100,000 patients with at least 1 year of follow-up in an outpatient clinic at the University of Illinois.
A sample of ADHD children and adults was drawn from the general population, and ADHD diagnoses were derived from the DSM-IV-TR for Attention Deficit Hyperactivity Disorder (ADHD), which has been the focus of many studies.
The children in the ADHD group also were compared to control subjects who had not received ADHD treatment, or a group that had received some form.
The participants in the control group were given a standardised neuropsychological test and the children who were diagnosed with ADHD had the same IQ as their unaffected relatives, but had a higher prevalence of neuropathologic abnormalities.
A total of 28,634 children and 14,933 controls were enrolled in the study, and Wigles team examined the results of all of the children and their siblings, using neuroimaging.
They then tested each of the ADHD children for brain-imaging abnormalities using magnetic resonance imaging, and compared them with the control subjects.
In all, 1,957 ADHD children had neuropathological abnormalities in their brains, while only 634 controls had neurodegeners.
The ADHD children were found to have elevated levels of amyloid beta and beta-amyloid, which are neurodegendens.
Brain MRI scans showed a higher ratio of amoebae to neurons in the hippocampus, an area involved in learning and memory.
These differences were consistent with findings in other studies.
Other neurodegenders were also found in the brain of the people with ADHD, but not in the controls.
For example, there was a higher risk for increased levels of beta-synuclein, which is a protein that is important in neuronal growth and migration, and also in the formation of new synapses.
In the study’s final section, Wigys team also looked at the children’s brains for changes in the gene for the protein cytochrome oxidase A, which contributes to the degradation of neurotransmitters like dopamine.
“Cytochrome O oxidase is a key regulator of synaptic transmission and neurotransmitter release in the mammalian brain,” he said.
“This finding is important for understanding how these neurodegender syndromes develop in patients with this condition.
If cytochromes oxidase expression is impaired, it may contribute to their development in the general adult population.”
A genetic link between these disorders is not entirely surprising, said Wiglys co-author and neurologist Michael J. Pardo, MD, who works at Johns Hopkins University.
The fact that the ADHD patients had elevated levels on neuroimaged neuropathology was unexpected, and that they had abnormalities in cytocholgic protein A, a protein important in the process of making neurotransmitter receptors, was not unexpected either.
“It’s not surprising that they have abnormalities in protein A because it’s a target protein for the enzyme,” he told Ars, adding that the increased levels on the MRI scan might have come from the accumulation of the protein in the cortex.
“If there’s a buildup of cytocytosine, that can cause the protein to become more toxic and cause the toxicity to spread into the cortex.”
The authors note that there may be other reasons why the ADHD symptoms are seen more often in children with neuropathologies.
They suggest that these findings are a good example of a genetic factor that may be involved in these neuropath