The question, "What causes ADHD?" has no simple answer. Nonetheless, the causes of ADHD are the same whether we are speaking of a child or an adult. Despite intensive research over the last 20 years, we still cannot say, with any precision, the exact cause(s) of ADHD. Most professionals agree that ADHD is a brain-based, or neurological, disorder. This means the brains of people with ADHD seem to work a little differently than that of other people. For example, people with ADHD may produce less of the neurotransmitter dopamine while also having more dopamine receptors. Researchers suspect that low dopamine levels are related to ADHD symptoms.
We do know ADHD has a large genetic component with numerous gene variations in people with ADHD, when compared to people without ADHD. In fact, ADHD has a heritability rate of 75%. Stated differently, this means only 25% of ADHD causes can be attributed to causes that are not genetic. It is important to highlight the ramification of this strong genetic component: Many of the parents of ADHD children most likely have ADHD themselves. A critical part of the treatment plan for these children is that their parents learn to manage their own symptoms. This empowers them to teach the children how to do the same.
Since the causes of ADHD are the same for children and adults, we direct you to our companion article on childhood ADHD for a more thorough discussion of this topic.