It’s not known why some children develop ADHD. There could be a genetic predisposition, but no single gene or combination causes ADHD. It’s possible that problems during fetal development that affect your central nervous system (brain and spinal cord) could be responsible in some cases.
Your chances of developing ADHD are higher if you were exposed to certain toxins, such as lead, when you were a child. If your mother had substance abuse problems, that could also increase your risk of having ADHD.