The Cause of ADD/ADHD is Genetic
The scientific community now generally accepts that ADD/ADHD is a genetic disorder.
This is gratifying to me because, back in 1980, I studied eighteen families in which I diagnosed one parent to have ADD/ADHD but not the spouse. All of the ADD/ADHD parents were treated successfully with medication as were 22 of the children of these families. There was a total of 48 children in these 18 families. It was apparent from this pilot study that ADD/ADHD inheritance is best described as genetic and consistent with autosomal dominant inheritance. This conclusion was reasonable because approximately half of the boys and girls had ADD/ADHD when only one of their two parents had ADD/ADHD.
A search for the gene or genes that cause ADD/ADHD goes on. This search can be fruitful, however, only if is fully appreciated that there are people with ADD/ADHD brain chemistry and behaviors who live very functional lives in a forgiving environment and a second group with ADD/ADHD brain chemistry who live in an environment that is hostile to their behavioral characteristics. In the latter group, ADD/ADHD is properly considered a "disorder" and commonly treated medically. From a genetic point of view, however, both those with and those without significant dysfunction should be recognized as having ADD/ADHD brain chemistry.
While neuroscientists are still working on finding the gene or genes that cause ADD/ADHD brain behaviors, we can at least feel confident that such ideas as the stress of childbirth, exposure to illicit drugs, drinking alcohol while pregnant, emotional trauma to the mother or child, or other environmental and psychological influences do not "cause" ADD/ADHD.