NIH: Brains of people with ADHD differ from those without disorder

Nov. 16 (UPI) -- People with attention deficit hyperactivity disorder have patterns of gene activity in their brains that differ from people without the condition, researchers from the National Institutes of Health said Wednesday.

NIH said this is the first study to use postmortem brain tissue to investigate ADHD, a condition in which a person may be hyperactive and have difficulty concentrating and controlling impulses.

The new study's findings, which were published in the journal Molecular Psychiatry, indicate how genomic differences might contribute to ADHD symptoms, NIH said in a news release.

Scientists found that people diagnosed with ADHD had differences in genes that code for neurotransmitters -- chemicals used by brain cells to communicate with one another. Specifically, they found differences in gene expression for glutamate neurotransmitters, which are important for brain functions such as attention and learning.

NIH described ADHD as "a highly heritable," or inherited, disorder since roughly 70% of the affected phenotype is explained by genetic factors.

Genomics, therefore, is at the core of understanding ADHD, NIH said.

In the United States, ADHD is one of the most common neurobehavioral disorders of childhood, the Centers for Disease Control and Prevention says.

The condition affects about 6 million children between ages 3 and 17, or 1 in 10 children, according to the CDC's latest available data.

While imaging via brain scans of people with ADHD allows researchers to examine the structure and activation of areas of the brain, NIH explained that such studies "lack information at the level of genes and how they might influence cell function and give rise to symptoms."

In other words, NIH said, researchers have been able to identify genes associated with ADHD, but unable to determine how differences in these genes act in the brain to contribute to ADHD symptoms -- until now.

The study, led by scientists at the National Human Genome Research Institute, a part of NIH, looked at the post-mortem brain tissue of 60 people, some with ADHD and some without.

The investigators used a genomic technique called RNA sequencing to explore gene expression -- how specific genes are turned on or off.

Their focus was on two connected brain regions associated with ADHD and critical in controlling a person's attention, the caudate and the frontal cortex, since previous research has found differences in the structure and activity of these brain regions in people with ADHD.

The study "allows us to inch closer to understanding how genomic differences alter gene expression in the brain and contribute to ADHD symptoms," Dr. Philip Shaw, senior investigator in the Social and Behavioral Research Branch in NHGRI's Intramural Research Program, who supervised the study, said in the release.

Gustavo Sudre, who led the study, said multiple types of genomic studies are "pointing towards the expression of the same genes" for ADHD.

Sudre, associate investigator in the Social and Behavioral Research Branch in NHGRI's Intramural Research Program, said that the gene-expression differences "were similar to those seen in other conditions, which may reflect differences in how the brain functions, such as in autism."