ADHD and Genetics

Attention Deficit Hyperactivity Disorder (ADHD) affects between three and five percent of American children. It is more common in boys than girls, and often persists into adulthood. Children with ADHD may also have other learning disorders and behavioral problems such as anxiety, defiance or tics. ADHD is characterized by:

• impulsivity
• inattention
• hyperactivity.

All children show these behaviors at one time or another. If these symptoms continue over time, a health professional should be consulted for a possible ADHD diagnosis.

Types of ADHD

ADHD can present itself in a variety of ways. There are three main subtypes of ADHD:

• predominantly hyperactive-impulsive: Children are hyperactive and impulsive, but not inattentive. These children are constantly running around, fidgeting and touching everything they can get their hands on. To be diagnosed with this condition, symptoms must be severe enough to be disruptive and have persisted at least six months.
• predominantly inattentive: Children with this subtype have been disruptively inattentive (but not hyperactive) for at least six months. These children often appear to be daydreaming and have difficulty processing oral or written instructions.
• combined: Children with combined ADHD have disruptive symptoms of both inattention and hyperactivity which have persisted for at least six months.

Causes of ADHD

No one knows the exact cause of ADHD, and it is important for parents not to blame themselves if their children have this learning disorder. ADHD is complex and may have a number of causes, both environmental and genetic. Here are some environmental factors which may contribute to ADHD:

• brain injury (pre or post-natal), especially to the frontal lobe
• lead exposure
• maternal smoking
• nutritional deficiencies such as lack of omega-3 oils.

Research has found a genetics linking to ADHD. Many current studies focus on the brain chemical dopamine, which has been found at lower than normal levels in those with ADHD. Some ADHD genes have already been identified, including the dopamine genes DAT1 and DAT4.

ADHD Genetics Family Studies

Families are often studied to determine if a condition is genetically caused. Dr Joseph Biederman conducted a study of families with ADHD and learned that more than a quarter of first degree relatives of children with ADHD also had ADHD. In control groups, the rate was only 5 percent.

Adoption studies by Dr. Dennis Cantwell further support the evidence that ADHD is genetically influenced. His research compared hyperactive children with both their adoptive and biological parents. The children's activity levels were found to be more similar to their biological parents than to their adopted ones.

Studying Twins

Twin studies have also been important in establishing the heritability of ADHD. Genetic conditions are more likely to appear in pairs of identical twins (who share an identical genetic profile) than in fraternal twins (who have close, but not identical profiles). A study of 1,938 families conducted in Australia by Dr Florence Levy found that ADHD had a concordance rate of 82 percent in identical twins, and 38 percent in fraternal twins, supporting a genetic cause.

Treatment of ADHD

ADHD is currently treated with stimulant medications such as Adderall and Ritalin, which normalize brain activity and help children focus. Other treatment options include:

• parent skills training to help manage ADHD behaviors in children
• social skills training
• support groups
• therapy (behavioral and psychological).

In the future, genetics for ADHD may be fully understood and lead to even more effective management of this challenging condition.

Resources

Grohol, John (2007).An Introduction To ADHD. Retrieved September 17, 2008, from the PsychCentral Web site: http://psychcentral.com/disorders/adhd/.

Grohol, John (2007).Symptoms Of ADHD. Retrieved September 17, 2008, from the PsychCentral Web site: http://psychcentral.com/disorders/adhd/adhd_symptoms.htm.

Martin, Ben (2007).Causes Of ADHD. Retrieved September 17, 2008, from the PsychCentral Web site: http://psychcentral.com/disorders/adhd/adhd_causes.htm.

Martin, Ben (2007). Future Directions In ADHD. Retrieved September 17, 2008, from the PsychCentral Web site: http://psychcentral.com/disorders/adhd/adhd_outlook.htm.

MyADHD (n.d.). Causes Of ADHD. Retrieved September 17, 2008, from the MyADHD Web site: http://www.myadhd.com/causesofadhd.html.