Attention-Deficit/Hyperactivity Disorder: Causes of ADHD
What brain changes occur with ADHD? continued...
One dopamine study focused on the genetics of ADHD -- specifically, on a particular variation of the DRD4 gene. This gene is associated with a dopamine receptor in the brain. What the study showed is that children with ADHD are more likely to have a certain variation of the DRD4 gene than children without ADHD. Interestingly, not all kids with ADHD in the study had the DRD4 gene variation. But those who did generally had higher IQ scores than other children with ADHD. Plus, the gene variation was most common in children whose ADHD improved over time.
Another dopamine study involving adults with ADHD showed that adults with ADHD had a sluggish dopamine system. The study helped explain why stimulant ADHD medications such as Ritalin and Adderall are beneficial. Stimulant ADHD medications increase dopamine by strengthening the weak dopamine signals in the brain. That counters the decreased brain dopamine activity in adults with ADHD. In addition, drugs of abuse, like nicotine and cocaine, temporarily increase brain dopamine activity. So the study authors hypothesized that the decreased dopamine activity associated with ADHD may help explain why people with ADHD may have a greater risk of drug abuse.
What role do environmental toxins play in ADHD?
The presence of certain toxins in the environment, such as lead, PCBs, or pesticides, may also have a role in causing ADHD. Researchers believe that some toxins may interfere with the brain development of children. That, they say, could possibly lead to ADHD.
Can watching too much TV cause ADHD?
Past studies suggested the possibility that too much TV may be associated with ADHD. But some newer studies show that time spent watching TV may not affect young kids' risk of developing ADHD.
In one study, experts reviewed data from a national survey of parents, teachers, kindergarteners, and first-grade students. They concluded that kindergartener's TV time was not linked to the chance of having attention problems in first grade.
Are there prenatal risks associated with developing ADHD?
Studies show pregnant women who smoke or drink alcohol may have an increased risk of having a child with ADHD. Some studies also show that women who smoke during pregnancy are more likely to have ADHD themselves. Other studies conclude that alcohol or drug abuse during pregnancy can reduce the activity of dopamine transmission between nerve cells in brain areas that regulate attention
In addition, ADHD is higher in children who had a low birth weight or whose mothers had difficult pregnancies.