Up to 10 million American adults have attention deficit hyperactivity  disorder (ADHD)—also commonly referred to as ADD—so it’s no surprise that some  of America’s most acclaimed athletes, actors, and musicians make up part of that  mix. Left untreated, the disorder is characterized by poor concentration and  disorganization, and can lead to emotional and social problems.

About 60 percent of children diagnosed with ADHD will continue to experience  these symptoms well into adulthood. And some people with the disorder don’t  receive an official diagnosis until middle age.

See which celebs have suffered with an ADHD diagnosis since childhood, and  which have learned to manage their disorder as adults.

1. Michael Phelps The 25-year-old Olympic swimming sensation is  famous for his incredible focus in the pool, so it’s hard to believe he has  struggled with ADHD since childhood. His teachers complained about his inability  to sit still until, in fifth grade, the Phelps’ family physician formally  diagnosed him with ADHD. At age 9, Phelps went on Ritalin; his mother, Debbie,  later recalled in the New York Times that it seemed to help his hyperactivity.  After two years on medication, however, Phelps said he felt stigmatized (each  day at lunchtime he had to visit the school nurse to get his medicine) and asked  to be taken off the drug. After consulting with his doctor, Debbie agreed to let  him be med free.

Instead, Phelps used swimming to help him find focus. In fact, many children  with ADHD benefit from competitive sports. “I’m just different in the water,”  Phelps told Sports Illustrated. “I just feel at home in it.”

2. Solange Knowles The soulful songstress says she’s always been  full of energy, and claims that sometimes her sporadic speech and effervescence  led people to believe she was on drugs. The real culprit? ADHD.

Knowles, whose older sister is the popular singer and actress Beyoncé, said  she was diagnosed with the disorder twice before she believed it. “I didn’t  believe the first doctor who told me,” she has said. “I guess I was in  denial.”

Traditionally, ADHD was thought to be a male-oriented disease, and men were  once believed to account for the vast majority of cases. But recent research has  begun to focus on how the disorder affects females, so that ADHD may be  identified earlier in women’s lives.

3. Ty Pennington The energetic and upbeat star of ABC’s Extreme  Makeover: Home Edition said he was “uncontrollable” as a child unless he had  a crayon and piece of paper in hand. Pennington, 44, earned poor marks  throughout high school and college, until he was diagnosed with ADHD as an  undergrad.

“I’m about as ADHD as you can get,” Pennington told InStyle magazine.  He went on medication following his diagnosis and saw an instant improvement in  his schoolwork. “I immediately stared getting straight A’s. It changed my  life!”