There is no single cause of ADHD; rather, there are a range of factors relating to people’s genes, neurobiology (the structure and function of the brain) and environment that increase their chances of developing ADHD.
Genes
There appears to be a strong genetic component to ADHD. ADHD runs in families and having a relative with the disorder is one of the strongest risk factors.
Neurobiological factors
In adults with ADHD, research has found some differences in areas of the brain and brain activity that relate to short term memory, the ability to focus, and the ability to make choices.
Differences have also been found in brain activity associated with attention and self-regulation, that is, the ability to focus attention, as well as manage emotions, thinking and behaviour.
Environmental factors
Certain environmental factors might also play a role in the development of symptoms of ADHD. These include:
• Pregnancy and birth factors: Maternal smoking, alcohol and substance misuse, and stress during pregnancy, as well as low infant birth weight and prematurity are all factors linked to ADHD.
• Certain environmental toxins: Toxins such as lead can affect brain development and behaviour and have been linked to ADHD.
• Dietary factors: For some people (even without ADHD) attention and concentration might be affected by nutritional deficiencies (e.g., zinc, magnesium, polyunsaturated fatty acids) and sensitivities to certain foods (e.g., sugar, artificial food colourings). There is no evidence however that these cause ADHD and a medical practitioner should be involved to evaluate these issues if they are considered of possible concern.