Attention deficit hyperactivi... Health Article

Genetic profile

There is good evidence to suggest that genetic factors play an important role in ADHD. From early studies to the present, it has been recognized that ADHD tends to run in families. Multiple studies have shown that patients who have first or second degree relatives with ADHD are at higher risk for developing ADHD then patients who do not have close relatives with the condition. It has also been shown that children who are adopted are at higher risk for ADHD if their biologic parents have the condition, rather than their adoptive parents. Children whose parents have ADHD have a 50% chance of developing the condition.

While genetics certainly plays a role in ADHD, the specific genes responsible for the condition have yet to be identified. In 1993, a study reported that ADHD was seen in 40% of adults and 70% of children in a rare thyroid autosomal dominant disorder located on chromosome 3. However, later studies have been unable to confirm this initial study.

More convincing research points to a particular form of a gene called DRD4-7, which codes for dopamine transport in the brain. Dopamine is one of several very important brain neurotransmitters, and a certain type, or allele of DRD4-7 is thought to decrease the amount of dopamine in the brain. Studies have shown that about 30% of patients with ADHD have this certain DRD4-7 allele. In people who do not have ADHD, this allele is only seen about 15% of the time.

Demographics

Studies on the occurrence of ADHD within different ethnic, racial, and sociological groups is somewhat limited. Early studies pointed to families on the lower end of the socioeconomic scale and minority racial groups as having a higher incidence of ADHD. However, later studies have not bore these studies out, and in fact there was obvious ethnic and racial bias built into these initial studies.

More recent studies have focused on possible enviromental factors in the development of ADHD. Childhood exposure to certain toxins, such as lead, alcohol, and cigarette smoke, seemed to be linked to a higher occurrence of ADHD. Other studies point to childhood hypersensitivity to certain food additives as a contributing factor in the development of ADHD. Nutritional deficiencies in iron, zinc, and essential fatty acids have also been implicated in ADHD, but studies in this area are limited.