Attention-deficit/hyperactivity disorder occurs when a person experiences difficulties with maintaining attention or controlling physical energy and movement. In the United States, approximately 8.4 percent of children have attention-deficit/hyperactivity disorder (ADHD). Around 2.5 percent of adults have ADHD.In some children, ADHD symptoms begin as early as 3 years of age, according to the National Institute of Mental Health. However, many different life events, psychological disorders, and medical conditions can lead to certain characteristics of ADHD. Even if the individual receives a diagnosis, ADHD is manageable and treatment can be highly effective.It's normal for children to occasionally forget their homework, daydream during class, act without thinking, or get fidgety at the dinner table. But inattention, impulsivity, and hyperactivity are also signs of attention deficit hyperactivity disorder (ADHD), sometimes known as attention deficit disorder or ADD.ADHD makes it difficult for children to inhibit their spontaneous responses that can involve everything from movement to speech to attentiveness. We all know kids who can't sit still, who never seem to listen, who don't follow instructions no matter how you present them, or who blurt out inappropriate comments at inappropriate times. Sometimes these children are labeled as troublemakers, or criticized for being lazy and undisciplined. However, they may have ADHD.It can be difficult to distinguish between ADHD and normal "kid behavior." If you spot just a few signs, or the symptoms appear only in some situations, it's probably not ADHD. On the other hand, if your child shows some ADHD signs and symptoms that are present across all situations at home, at school, and play it's time to take a closer look. Life with a child with ADHD can be frustrating and overwhelming, but as a parent, there is a lot you can do to help control symptoms, overcome daily challenges, and bring greater calm to your family.