Brains of Children with ADHD Show Protein Deficiency
New research on children with attention deficit/hyperactivity disorder has found a deficiency of a necessary brain chemical. Children with ADHD appear to have nearly 50 percent lower levels of an amino acid called tryptophan, a protein which helps in the production of dopamine, noradrenaline, and serotonin. It also is important for attention and learning.
Jessica Johansson of Orebro University in Sweden and her team set out to investigate whether children with ADHD show differences in the transport of the proteins tryptophan, tyrosine and alanine, since these amino acids are the precursors for brain chemicals which have already been implicated in the development of ADHD.
They analyzed connective tissue cells called fibroblasts from 14 boys ages 6 to 12, each of whom had ADHD. It turned out that the cells’ ability to transport tryptophan is lower in boys with ADHD than in other boys.
The finding could suggest greater biochemical disturbances in the brains of people with ADHD than previously realized, Ms. Johansson said. She commented, “This indicates that several signal substances are implicated in ADHD, and in the future this could pave the way for other drugs than those in use today.”
She explained that her work focuses on analyzing important signaling substances in the brain. Excessively low levels of these substances may lie behind the development of conditions such as ADHD.
The findings “probably mean that the brain produces less serotonin,” she said. “Thus far the focus has mainly been on the signal substances dopamine and noradrenaline in the medical treatment of ADHD. But if low levels of serotonin are also a contributing factor, other drugs may be necessary for successful treatment.”
Low serotonin could contribute to greater impulsivity, she added, which is a core symptom of ADHD. More investigation into serotonin in people with ADHD and disruptive behavior disorders is urgently needed, she believes.
The children in the ADHD group also had increased transport of the amino acid alanine in their fibroblast cells. It is unclear how this affects ADHD, the experts say, but they suggest it might influence the transport of other amino acids important for normal brain activity.