Attention Deficit Hyperactivity Disorder: Overview and Risk Factors

Attention deficit hyperactivity disorder (ADHD) is characterized by difficulty maintaining attention, by hyperactivity and impulsive behavior, or by a combination of these symptom categories. It affects 5 to 10 percent of children, and up to 70 percent of cases continue into adolescence and adulthood. It may be associated with other psychiatric conditions, such as learning disabilities, anxiety, depression, and, later in life, substance abuse. About half of cases begin earlier than age 4.

The disorder is probably caused by a combination of genetic and environmental factors.

Risk Factors

• Male gender: ADHD appears to be two to three times more common in boys than in girls.
• Genetics: Some studies indicate that as much as 75 to 80 percent of risk may be genetic. Several genes have been identified as possible candidates.
• Environmental factors: Early lead exposure or head injury may increase the risk.