The exact cause of attention deficit hyperactivity disorder (ADHD) is not fully understood, although a combination of factors is thought to be responsible.
ADHD tends to run in families, and in most cases, genes inherited from parents are thought to be a significant contributor to the disorder.
Research shows that parents and siblings of people with ADHD are more likely to have ADHD themselves.
However, the way ADHD is inherited can be complex and is not thought to be related to a single genetic defect.
brain function and structure
Research has found that the brains of people with ADHD may have some differences from those of normal people, although the exact significance of these differences is unclear.
For example, studies involving brain scans suggest that some areas of the brain may be smaller in people with ADHD, while other areas may be larger.
Other research suggests that neurotransmitter levels in the brains of people with ADHD may be imbalanced, or these chemicals may not function properly.
groups at risk
Certain people are also thought to be more susceptible to ADHD, including:
- People who were born prematurely (before 37 weeks of pregnancy) or had a low birth weight
- have epilepsy
- Brain injury – occurs in utero or after a serious head injury later in life