Attention deficit hyperactivity disorder, or ADHD, affects approximately 5 percent of the population. The 1994 edition of the American Psychological Association's "Diagnostic and Statistical Manual of Mental Disorders" retired the term ADD, or attention deficit disorder, and uses the term ADHD exclusively to define the condition. People suffering from this affliction show an inability to pay attention, excessive daydreaming, irritability, hyperactivity and impulsive behavior, and often exhibit school- and work-related behavioral problems.
Genetics
Studies of twins and families with ADHD reveal that the disorder has a very strong genetic basis, according to MyADHD.com, which cites the following: In a study published in the "Journal of the American Academy of Child and Adolescent Psychiatry" in 1990, Dr. Joseph Biederman of Massachusetts General Hospital found that a person with ADHD has a 25 percent chance of having an immediate family member with ADHD. Australian researcher Dr. Florence Levy and her colleagues published a study in the "Journal of the American Academy of Child and Adolescent Psychiatry" in 1997 that found that if one identical twin has ADHD, the other has an 82 percent chance of also having it. While family members of an ADHD patient may not qualify for a diagnosis of the disorder, they will exhibit some symptoms of ADHD.
Toxic Substances
In a study published in 2006 in the journal "Environmental Health Perspectives," J. M. Braun and colleagues found that exposure to lead correlates with ADHD diagnosis. They also found that maternal smoking during pregnancy increases the risk of a child's developing ADHD.
Premature Birth and Low Birth Weight
Children born prematurely and with a low birth weight have a higher rate of ADHD, according to Dr. Karen Linnet and colleagues at the Perinatal Epidemiology Research Unit in the Department of the Obstetrics and Pediatrics at Denmark's Aarhus University Hospital. Aaron Levin reported in the Aug. 4, 2006, issue of "Psychiatric News" that their study found children with a gestation period of less than 34 weeks to be three times more likely to be diagnosed with the disorder later on. Children born four to six weeks early were 80 percent more likely to have ADHD. Those whose births followed normal gestation periods but who had low birth weights also showed higher risk for the disorder.
Nutrition
"The idea that refined sugar causes ADHD or makes symptoms worse is popular, but more research discounts this theory than supports it," according to the National Institute of Mental Health. Dr. John E. Huxsahl, writing at MayoClinic.com, says, "There's no evidence that food additives cause attention-deficit/hyperactivity disorder, but an increasing number of studies show that certain food colorings and preservatives may cause or worsen hyperactive behavior in some children." On the other hand, "Some preliminary studies suggest that deficiencies of certain nutrients, including iron, zinc, magnesium, and vitamin B6, are associated with ADHD-like symptoms," according to Dr. Carl Sherman in the Feb.-Mar. issue of "ADDitude" magazine.
Brain Anatomy
People with ADHD have anatomically distinct differences in their brains compared with normal people's. In a study published in "The Lancet" in 2003, a team of neuroscientists at UCLA led by Dr. Elizabeth Sowell, discovered that ADHD patients showed a reduced size in the frontal lobe, an area of the brain that plays an important role in planning, organizing and monitoring behavior. Children with ADHD have smaller temporal lobes and an overall brain size 3 to 4 percent smaller than normal children's.
