Many adults believe that Attention Deficit and Hyperactivity Disorder (ADHD) is a behavioral problem caused by permissive parents or misbehaved children. This is however not the case, according to the National Resource Centre on ADHD no strong evidence exists connecting bad parenting with ADHD. Although circumstances and parenting styles can mitigate or aggravate the behavioral problems, the cause of ADHD is thought to be a combination of genes and environmental factors. Diet was once also considered a possible cause, but most of the suspected dietary causes have been ruled out.
ADHD sufferers have a problem with the way the neurotransmitters in their brains work. Neurotransmitters are chemicals in the brain that make it possible for nerve cells to communicate with one another. In ADHD sufferers, there are insufficient neurotransmitters in the area of the brain that are responsible for regulating attention and behavior.
Research into brain volume
In the biggest study that they have ever carried out, Radboud University Medical Centre in the Netherlands studied 1713 ADHD sufferers and 1529 non-sufferers between the ages of two and sixty-three. Sufferers and non-sufferers were all subjected to MRI scans to measure brain volume. Researchers found structural differences between the brains of sufferers of ADHD and non-sufferers. The sufferers had smaller brain volumes than non-sufferers. Smaller areas were located in five different regions of the brain, pointing to the fact that ADHD is neurobiological in origin.
The biggest weight difference was in the amygdala, the area of the brain that controls emotions. The areas believed to cause ADHD are located in the basal ganglia, which controls emotion, perception, and voluntary movement. The differences in brain volume are very small, but similar differences are seen in the brains of people suffering from other psychiatric disorders. There was a much bigger difference in volume between the children than the adults, suggesting that ADHD is caused by a delay in development in these areas of the brain A recent study published in the Lancet Psychiatry has suggested that ADHD should be regarded as a brain disorder because it is associated with delayed development in five areas of the brain.
Differences in DNA
In 2010 scientists at Cardiff University studied the genomes of 366 children who had been diagnosed with ADHD and 1000 children who did not have the condition. They hoped to discover whether there was any difference in the DNA of children with the condition. What they found was that the children with ADHD had missing or duplicated pieces of DNA. They also found that there was a significant overlap between these segments and those of children suffering from schizophrenia and autism. The scientists found that these discrepancies in DNA were twice as common in children with ADHD than in those who did not have this condition, proving that ADHD is a neurodevelopmental problem. This was the first direct genetic link. ADHD is considered as one of the most common mental disorders in children.
Prior to this research project, scientists were already aware that there were genetic links to ADHD. Tests had shown that when one identical twin had ADHD, the other would almost certainly show symptoms. It was also known that a parent who had been diagnosed with ADHD was on average more likely to have a child diagnosed with the same disorder.
There are other factors that are known to cause ADHD. It can result from injury to the brain either at birth or after. Environmental factors are seldom the cause of ADHD but a stressful environment can cause symptoms that mimic the behaviors. The use of drugs, alcohol, and cigarettes by the mother during pregnancy is also known to be a cause. Research suggests that smoking in pregnant mothers can increase the incidence of ADHD 2.4 fold. Premature delivery and low birth weight are also possible causes of ADHD.
ADHD may be a psychiatric disorder that is most likely to be inherited. If a child has a parent with ADHD, he has a 50% chance of having it. Those who have severe ADHD may have smaller brains and may have different neural pathways in areas that control impulse control, concentration and motor activity. Environmental factors such as poor home environment or conflict in the home can influence the severity of symptoms, but they do not give rise to the disorder.