About 4 percent of adults have attention deficit hyperactivity disorder (ADHD), and many others have never been diagnosed. (About half of kids with ADHD still have it in adulthood.)
A diagnosis can be important. Adults with ADHD tend to have lower incomes as well as higher rates of accidents, unplanned pregnancies, and substance abuse than those without it, says Dr. Martin W. Wetzel, an assistant professor of psychiatry at the University of Nebraska Medical Center, in Omaha.
Children with ADHD can be overly energetic, but adults may just feel edgy or restless.
"Adults don't show the more obvious signs such as running and jumping," says Colette de Marneffe, PhD, a clinical psychologist in Silver Spring, Md. "Hyperactivity presents more subtly in the form of restlessness."
However, you may recall a rambunctious childhood. Dr. Wetzel had a patient who recalled spending a lot of time in the school hallways because "he couldn't sit still." It's a "classic story," he says.
ADHD appears to have a genetic component. When one member of the family has it, there's a 25 percent to 35 percent chance that someone else in the family does, too, according to the Attention Deficit Disorder Association.
When a child is diagnosed with ADHD, some adults, who may have had the same symptoms when they were children, realize that they may have always had the condition without realizing it.
A newly minted relationship is often exhilarating, but the novelty can wear off in time.
"Oftentimes adults with ADHD really have a hard time with that transition," notes de Marneffe. "When the relationship becomes more stable and predictable, conflicts tend to emerge."
Being easily distracted or inattentive - symptoms of ADHD - can also sabotage existing relationships with family, friends, and significant others who view their loved one's behavior as self-centered, Dr. Wetzel adds.
About 40 percent of adults with ADHD smoke, versus only percent of the general population.
"Nicotine is very effective for a lot of ADHD symptoms and it's not uncommon for me to see someone for the first time after they quit smoking," says Dr. Wetzel. That's because they often start to have more problems with focus and concentration, he explains.
Adults with ADHD are also more likely to use alcohol and other drugs, and at earlier ages, than people without ADHD.
If you suspect you have ADHD as an adult, an early history of ADHD symptoms - difficulty sitting still, paying attention to the teacher, and focusing on your work, for example - can confirm the diagnosis.
"What adult patients will tell you over and over and over again is that they had to work twice as hard as their peers to get half as much done in school," Dr. Wetzel says.
"I can't tell you how many times a patient has told me, 'I'm the king of procrastination,' or 'I'm the queen of procrastination,' because they feel like no one else can put things off like they can," says Dr. Wetzel.
It makes sense, he adds, because when people with ADHD are under the gun and anxious, that's when they can focus. Constant anxiety, however, can be very stressful.
People with ADHD are often drawn to activities that are stimulating. They may engage in risky behaviors, like fast driving, gambling, and even extramarital affairs.
The key is to channel that desire for excitement and novelty into activities that don't jeopardize your work and family life, says de Marneffe. Parasailing or other high-adventure activities may be good outlets.
Everyone encounters some task he doesn't particularly enjoy, but most people are able to find a way to complete the boring aspects of their job, says de Marneffe. People with ADHD, however, have a hard time doing that.
Jobs with a lot of repetition tend to be a poor fit, she observes. Choose work that engages you and fulfills your need for novelty and variability.
Is your house cluttered with piles of laundry? Is your expense account still a work in progress? Failing to finish tasks can be a symptom of ADHD in adults.
Dr. Wetzel, author of the e-book "The Adult ADHD Handbook For Patients, Family & Friends," finds the most successful ADHD patients tend to be entrepreneurs who recognize this shortcoming and surround themselves with people who will focus on the details, finish the paperwork, and handle the mundane portions of a task.
Your spouse wants to catch a movie, but unless it's the thriller you've been dying to see, you may get up several times or have random thoughts that distract you from the plot.
Being calm requires a quiet mind, and that's tough for people with ADHD because "so many other things can take over their consciousness," Dr. Wetzel says. "People with ADHD will tell you it's almost impossible for them to meditate."
Here's the tip off: Your desk is a mountain of paper and you just wasted a half hour searching for an important legal document. Or maybe you failed to make appointments for your children to see the pediatrician, and the school wants their immunization reports - pronto.
If you have ADHD, getting and staying organized is a challenge for you. Breaking organizational tasks into smaller steps may help, according to the National Resource Center on ADHD, in Landover, Md.