What causes ADHD?

ADHD is a psychological disorder, common causes are 1, congenital genetic heredity. 2, pregnant women during pregnancy, often drink, smoke, or frequent exposure to ionizing radiation, causing damage to the fetus. 3, family relations are not harmonious. Children with ADHD, not only lead to slow growth and development of children, but also cause their self-confidence to decline, thus affecting future life and learning.