There is no single cause of ADHD; rather, there are a range of factors relating to a person’s genes, neurobiology (the structure and function of the brain) and environment that increase the chance of developing ADHD.
Genes
There appears to be a strong genetic component to ADHD, and ADHD often runs in families. Research suggests a number of genes might be involved, rather than one single gene.
Neurobiological factors
In children with ADHD, research has found some differences in areas of the brain and in brain activity that relate to movement, information processing, learning, memory, attention, and the regulation of emotions, thoughts and behaviour.
Environment
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.