Attention-Deficit/Hyperactivity Disorder (ADHD) is generally considered to be a developmental disorder, largely neurological in nature, affecting about 5% of the world's population. The disorder typically presents itself during childhood, and is characterized by a persistent pattern of inattention and/or hyperactivity, as well as forgetfulness, poor impulse control or impulsivity, and distractibility. Although often referred to in conjunction with Attention Deficit Disorder (ADD), ADD is, in fact, not a documented diagnosis, and this common misuse of the terminology actually refers to ADHD predominantly inattentive type.

ADHD is currently considered to be a persistent and chronic condition for which no medical cure is available. ADHD is most commonly diagnosed in children and, over

the past decade, has been increasingly diagnosed in adults. About 60% of children diagnosed with ADHD retain the disorder as adults. Studies show that there is a familial transmission of the disorder which does not occur through adoptive relationships however adoption-based studies are not reliable in this context.

Twin studies indicate that the disorder is highly heritable and that genetics contribute about three quarters of the total ADHD population, though such studies are have been criticized. While the majority of ADHD is believed to be geut 1/5 of all ADHD cases are thought to be acquired after conception due to brain injury caused by either toxins or physical trauma prenatally or postnatally.