Is ADHD hereditary?

Sam - Possibly, up to 60% or 70% of the expression of ADHD has to do with genes. Probably, there's many genes that each confer a small risk of developing ADHD. So, if you have many of these genes, you might be at heightened risk. The kind of genes that we find to be involved are those involved in brain function such as genes involved in the noradrenaline system and genes involved in the dopamine system. These are two chemical systems in the brain that help to regulate our cognitive abilities such as our ability to concentrate on things or supress impulsive behaviours.