He is the toddler in perpetual motion, his throttle wide open every waking moment of the day (and a good deal of the night). He runs, jumps, climbs, opens, closes, pushes, shoves, and bulldozes over playmates who seem nearly comatose by comparison.

He is the five-year-old whose kindergarten checkup is the major challenge of his doctor’s afternoon. If the appointment is delayed for only a few minutes, he will rapidly investigate every surface and piece of equipment within reach. Despite his haggard mother’s valiant efforts, permanent alterations of the room’s contents are likely.

She is the third grader who fidgets, squirms, and taps her fingers through most of the school day. Anything and everything – the hair ribbons adorning the girl in is front of her, the birds in the tree outside the classroom window, the sound of a passing truck, and a thousand other sights and sounds – distract her from whatever the teacher wants her to do. She can’t seem to listen to directions, finish any assignment, or cooperate in any game. Her list of friends is as short as her attention span.

He is the young adult who dropped out of school, just lost his job, and can’t maintain a relationship. His fuse is short (and he has a few scars to show for it), his moods are unpredictable, his apartment is a mess, and his calendar is empty. Depression and anger are his constant companions; drug and alcohol abuse could be waiting in the wings.

These vignettes illustrate variations on the theme called attention deficit/hyperactivity disorder (ADHD), which is estimated to affect at least 5 percent of American children. (This includes approximately 2 million school-age children, nearly one per classroom.) Boys with ADHD outnumber girls at least four to one – some experts state as much as nine to one. No statistics can remotely estimate the depths of frustration, disappointment, resentment, and guilt that the parents of these children feel, at least at times. Despite a common belief that this problem disappears during adolescence, it usually doesn’t go away, and millions of adults are probably affected as well. However, with help (and medication, when appropriate), adolescents and adults can learn to cope and live successfully with this condition.