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Attention deficit hyperactivity disorder (ADHD) is a common behavioral disorder that can occur in both children and adults. Research suggests that there may be a link between a dopamine imbalance in the brain and the development of ADHD.
According to the Centers for Disease Control and Prevention (CDC), 6.1 million children living in the United States in 2016 had received a diagnosis of ADHD. The symptoms of ADHD can vary from person to person, but they typically include difficulties with concentrating, paying attention, and controlling impulses.
It is not clear what causes ADHD, but scientists believe that genetics, certain environmental factors, and brain changes may play a role in its development. Researchers have also investigated the role of neurotransmitters, such as dopamine.
Multiple factors are likely to contribute to ADHD. According to the National Institute of Mental Health, risk factors for ADHD may include:
genetics and family history of ADHD
low birth weight
premature delivery
alcohol, tobacco, or drug use during pregnancy
exposure to toxins, such as lead, during pregnancy or early childhood
brain injury
Scientists have also been studying the role of dopamine in the development of ADHD. Dopamine is a type of neurotransmitter that has several important functions in the brain and body. There is an association between dopamine levels and several psychiatric and neurological disorders, including Parkinson’s disease.
Dopamine levels can affect a person’s mood, attention, motivation, and movement. Dopamine also regulates the brain’s reward system, with its levels increasing in the brain when a person experiences something pleasurable, such as eating food or having sex.
Experts initially believed that ADHD occurs as a result of low levels of dopamine, but they have since realized that the relationship is a little more complicated.
According to the Gulf Bend Center, people with ADHD may have a higher concentration of dopamine transporters in the brain. These transporters remove dopamine from brain cells. When there are more transporters in one area of the brain, they do this too quickly, which means that dopamine has less time to exert its effects.
Reduced levels of the neurotransmitters serotonin and norepinephrine may also contribute to the development of ADHD.According to the DNA Learning Center, a small study in 16 children and adolescents with ADHD found that medications that increase the availability of dopamine in the brain lead to the inhibition of the motor cortex, the brain region that controls voluntary movement.
This effect was more significant in children with a genetic variation called DAT1, which is a gene that usually increases the activity of dopamine transporters. These results suggest that genetic factors that affect dopamine transporters may play a role in the development of ADHD.
The DNA Learning Center also report on another study that compared the MRI brain scans of children with and without ADHD. The researchers found that the children with ADHD had a thinner cortex in the areas of the brain responsible for attention control.
The researchers behind a small 2013 study found that methylphenidate (Ritalin) increased dopamine levels in the brain and improved attention in adults both with and without ADHD.
They also observed that both groups of participants had an equivalent availability of dopamine receptors in the brain. They concluded that their results suggest that dopamine dysregulation is unlikely to be the leading cause of ADHD in adults.
In a study from 2015, researchers identified an association between genetic changes in the DAT1 gene and mood instability in healthy adults. Mood instability tends to be a persistent symptom in people with ADHD.
The treatment of ADHD often involves a combination of therapies.
The American Academy of Pediatrics (AAP) recommend teacher- or parent-administered behavior therapy as the first line of treatment for children aged 4–5 years. For children over the age of 6 years, the AAP suggest that doctors prescribe a combination of behavior therapy and medication.
Medication options for ADHD include both stimulant and nonstimulant drugs that can help improve a person’s symptoms and enhance functioning. Stimulants, which contain forms of amphetamine and methylphenidate, help with focus and attention. Experts also believe that these medications increase levels of dopamine in the brain.
The Food and Drug Administration (FDA) have also approved three nonstimulant medications for treating the symptoms of ADHD: atomoxetine (Strattera), guanfacine (Intuniv), and clonidine (Kapvay). Doctors typically prescribe these drugs for people who have problems when taking stimulants.