There is little evidence that ADHD arises solely from social factors or child-rearing methods. Most substantiated causes appear to fall in the realm of neurobiology and genetics. Causes of ADHD include:
Environmental: Studies have shown a possible correlation between the use of cigarettes and alcohol during pregnancy and risk for ADHD in the offspring of that pregnancy. Environmental agent that may be associated with a higher risk of ADHD are lead and pesticide exposure.
Genetics: Attention disorders often run in families, so there are likely to be genetic influences. Studies indicate that 25% of the close relatives in the families of children with ADHD also have ADHD, whereas the rate is about 5% in the general population.
Food Additives and Sugar: It has been suggested that attention disorders are caused by refined sugar or food additives, or that symptoms of ADHD are exacerbated by sugar or food additives. In 1982, the National Institutes of Health held a scientific consensus conference to discuss this issue. It was found that diet restrictions helped about 5% of children with ADHD, mostly young children who had food allergies. A more recent study on the effect of sugar on children, using sugar one day and a sugar substitute on alternate days, without parents, staff, or children knowing which substance was being used, showed no significant effects of the sugar on behavior or learning.