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What are the causes of ADHD?

Learn about the causes of ADHD.

Research points to various potential causes of ADHD. [©Shutterstock, 2010]
©Shutterstock, 2010
Research points to various potential causes of ADHD.

The causes of ADHD (attention deficit hyperactivity disorder) are not entirely avoidable. When a child is diagnosed with ADHD, parents sometimes blame themselves because the condition seems largely behavioral. For example, when a child acts out or misbehaves, it is all too easy to blame the parents. In fact, though, research suggests that genetic predisposition and biological differences play a significant part in determining who develops ADHD. Environmental factors also may contribute to ADHD, but this theory is still under investigation. Below is a breakdown of physical differences that individuals with ADHD show, as well as some potential causes for these differences.

Brain Structure and Activity

Studies of people with ADHD have shown that certain areas of the brain exhibit less activity or are slightly smaller than average. These differences are mainly seen in the prefrontal cortex, the basal ganglia and the cerebellum – the areas of the brain that inhibit behavior, sustain attention and control mood. National Institute of Mental Health (NIMH) scientists also have found that people with ADHD use less glucose in areas of the brain that control attention, which may contribute to attention problems.

Brain Chemistry

In people with ADHD, certain neurotransmitters (chemicals that help brain cells communicate with one another) seem to work differently than in other people. This is particularly true of the neurotransmitter dopamine, which is used widely throughout the brain. When neurotransmitters don’t work as they should, ADHD-related problems such as inattention, hyperactivity and impulsivity can result.


ADHD tends to run in families, and so genetics are likely a factor. Children who have ADHD usually have at least one close relative with the condition. In addition, at least one-third of all fathers with ADHD have children with the condition and the majority of identical twins share the ADHD trait.

Toxins in Utero

Research shows that a mother’s use of cigarettes, alcohol and other drugs during pregnancy can damage the fetus’s developing brain. Alcohol and nicotine may change developing nerve cells in important ways and lead to some of the behavioral problems associated with ADHD. Cocaine and crack use during pregnancy also seems to affect the development of brain receptors that control responses to the environment, which may lead to ADHD.

Toxins in the Environment

Toxins encountered in the environment after birth also can affect brain development and may lead to ADHD. Lead found in dust, soil and paint in areas where leaded gasoline or paint were once used can be a culprit. Some animal studies suggest a connection between lead and ADHD, but only a few human cases have been found.

Poor Nutrition and Food Additives

The role of nutrition in causing or exacerbating ADHD is under debate. Sugar and food additives have been suggested as possible spurs to the hyperactivity associated with ADHD. In 2007, the Food Standards Agency in the United Kingdom advised parents of children with hyperactivity that cutting certain artificial colorings from their diets might have a positive effect on behavior. A study by the U.S. National Institutes of Health showed, though, that a restricted diet benefitted only five percent of children with ADHD, mostly young children or those with food allergies.

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