"I just like the way it feels," Capel says. "It's a habit."
It's such a habit, in fact, that Capel shows off a thick callous on the underside of the middle joint of her right thumb.
Signs of ADHD in adults such as Capel often can be subtle and misconstrued, experts say. In children, the preponderance of symptoms are related to hyperactivity and impulsive behavior. In adults, the symptoms are often inattentiveness or a combination of impulsiveness and inattentiveness.
Of the 10 million U.S. adults (4.4 percent of the population) diagnosed with attention deficit disorder, only 11 percent have sought treatment in the past year, and only 25 percent were ever diagnosed with the psychiatric condition before age 18, according to survey data from the World Health Organization.
As late as the mid-1990s, despite a spate of best-selling books on the subject, hardly any adults were diagnosed. The reason, says Dr. David W. Goodman, director of the Adult Attention Deficit Disorder Center in Luthersville, Md., is that the manifestations mirror other conditions, such as anxiety and depression.
"Children are typically diagnosed because of disruptive behavior," Goodman says. "(Adults) that have inattention often get missed until their academic or life demands exceed their ability to compensate. They get diagnosed later in life because of disorganization, inattention, inefficiency and difficulty juggling multiple responsibilities."
The consequences stemming from a late diagnosis in adults are many: negatively affecting relationships, family and work life. A WHO report released earlier this year found that adults with ADHD on average miss more than three weeks per year in workplace productivity due to forgetfulness, lack of concentration and impulsiveness.
"They also are twice as likely to get divorces, three times as likely to be involved in criminal activity," Goodman says. "They are highly impulsive, and half have or have had a history of alcohol or substance abuse."
Yet many mental-health practitioners will not immediately think of ADHD as the cause, says Dr. Julie Schweitzer of the University of California-Davis M.I.N.D. Institute in Sacramento.
"We have to assess for anxiety, depression and every other potential psychiatric disorder," she says. "It takes a lot of work. We have to have some evidence it was prevalent since childhood."
It can take some detective work. Capel, diagnosed at age 37 in 1991, says she has her husband, John, to thank. Capel says her life wasn't in a shambles before then. But she hadn't reached her potential.
She wanted to be a psychologist since her undergraduate days at the University of Florida but could never muster the discipline to follow through on it. At the time she met John in the late 1980s, she had a master's degree and was working as an adolescent counselor at a residential treatment center in the Sacramento area.
When she and John, a psychologist, started dating, he had his suspicions.
"The ADD person can start anything. They just can't finish it," he says. "That was her. So I started looking into her background."
Adds Cass: "Back then, John would ask me, 'Were you a hyper kid?' I'd say, 'No, why?' Two months later, he'd ask again. I told him my mom yelled a lot. He asked what she yelled every day. I told him it was, 'Why can't you sit down and shut up?' I was driving her crazy."
The clincher, Capel recalls, is when John first saw her disheveled apartment.
"He went, 'Ugh!'"
Staging something of an intervention, John invited Cass to a monthly meeting of the support group CHADD (Children and Adults with Attention-Deficit/Hyperactivity Disorder) in Roseville, Calif.
"It was amazing. I sat in a group with 25 people and kept thinking, 'That's my story,' " she says.
Eventually, a doctor confirmed her condition. But she said the doctor at first balked at prescribing Ritalin, the stimulant often given to children with the disorder. Eventually, she was given a prescription for 5 milligrams -- a small dosage.
She remembers that day, Nov. 16, 1991, as a life-changing one.