(ISTOCKPHOTO)People with attention deficit disorder (ADHD) who aren't diagnosed in early childhood may begin to exhibit more obvious symptoms as they enter their teenage years. The increased demands of school, jobs, and new relationships may bring to the surface a teen's inability to stay focused, or his or her penchant for impulsive or irrational behavior.

A teenager with ADHD can have trouble adjusting to major life changes, says Adelaide Robb, MD, an associate professor of psychiatry and behavioral sciences at the George Washington University School of Medicine and Health Sciences.

"Any time the complexity of your life changes, it's tough for people with ADHD," she explains. "When you go off to college, for example, you have less of a support system; your parents aren't there. Your schedule is different every day, and a person with ADHD is going to have trouble remembering when they have class."

More about adult ADHD

At this age, adolescents may also want to be independent and rebel against their parents or society. When asked if she ever has patients who refuse to take medication, Dr. Robb replies, "Yes, all the time. They're called teenagers."

The following information from our A-Z Health Library discusses common symptoms and risks of ADHD in this age group.