BOSTON -- In the average American classroom, it's estimated that at least one child has attention deficit disorder -- or ADD.

NewsCenter 5's Heather Unruh reported that a genetic link has a lot of parents getting diagnosed, as well.

Kelly Rehman was in her late 30s when her two sons were diagnosed with ADD.

"These guys were diagnosed, and I thought that's the problem -- it's me, too," Rehman said. "I remember feeling very restless and antsy, and I couldn't sit still."

Rehman and her sons are getting treatment at the ADD Health and Wellness Center in North Andover. Dr Theresa Cerulli said this case is very common because ADD runs in families.

"The genetics are strong. ADD is almost as inheritable as height. For families, what that means is that if there's a child with ADD, there is one parent with ADD,"

I think my brother and my dad are probably ADD," ADD Health and Wellness Center's Dr. Theresa Cerulli said.

Like Rehman, Cerulli said a lot of adults were never diagnosed with ADD as children. It's estimated that 8 million adults have it, but only 25 percent know it.

"Adults and children that don't have the hyperactive and compulsive symptoms, it goes unrecognized," Cerulli said.

"I wasn't really hyperactive," Rehman said.

"You're losing your keys, missing appointments, forgetting to pick up the milk," Cerulli said.

Adults with ADD can be forgetful, fidgety, have difficulty following through on instructions and, oftentimes, are distracted

"You'll be in a conversation with an adult with ADD, and they will repeat the same question they just asked you because their mind just jumped to something else, and they didn't actually hear the answer, so they'll repeat the question," Cerulli said.

But Cerulli cautions that just because you're easily distracted or just because your child has ADD, it does not mean you have the disorder.

"You cannot develop this as an adult. That's just called stress. Everyday life, responsibilities, it has to be since childhood that the person has struggled with these differences," Cerulli said.

The Greater Boston ADD Health and Wellness Center has a free evaluation program.