You misplace your keys, waver between work assignments and YouTube, and daydream during conversations. Some of it’s normal—life can get pretty hectic—but how do you know if you have a more serious problem? For adults who have attention deficit hyperactivity disorder (ADHD), this chronic inattentiveness becomes debilitating.

“We see an influx of adults being diagnosed around age 38,” says Timothy Wilens, M.D., an associate professor of psychiatry at Harvard Medical School. “That’s right around the time people start multitasking more, juggling jobs, families, a home, and other personal obligations—and problems focusing and staying alert seem to get worse,” he says.

But not everyone who slacks on work or forgets appointments has ADHD; there are plenty of other reasons you may be losing focus. Here are five things that could be sucking your attention span dry. Plus: When you should consider seeing your doctor.

Technology overload

Your BlackBerry, computer, cell phone, and iPod all compete for your attention—no wonder you're distracted! To a certain point, your brain can act as secretary, keeping you organized and helping with time management. But the more multitasking you try to do, the harder it is for you to stay focused on any single task, research shows. Learning basic organizational skills, like writing down responsibilities and maintaining a day planner, can help alleviate these problems. So can taking a break from constant television, Internet, and e-mail inundation—or setting house rules about technology-free times after dinner or before bed, for example.

See your doc if: You consistently find yourself being pulled away from important tasks and not being able to get back to them, and you can remember being this way for most of your adult life—with or without the help of the Internet or a cell phone. When the brain's not functioning properly, you can't bounce from task to task without being easily distracted by thoughts or background activities, says Dr. Wilens.

Lack of sleep

If you’re missing out on sufficient shut-eye—most likely seven to eight hours a night—you’re probably irritable, dealing with mind fog, and have difficulty managing daily tasks. That’s a normal reaction, says Dr. Wilens. “By getting adequate rest, like hitting the sack earlier, you should get your focus back,” he says.

See your doc if: You or your partner have sleep problems or constantly wake up unrefreshed, suffer from constant moodiness, and have attention issues, such as a lack of focus or ability to stay alert. You could have an undiagnosed sleep disorder or might benefit from basic sleep hygiene tips. For adults with ADHD, missing out on sleep can make symptoms worse—and simply improving nighttime habits won’t fully eliminate them.

Poor job satisfaction

Sure, everyone’s unhappy at work from time to time—maybe your client presentation flopped or your boss gave you a poor performance review. And if a disorganized work environment or a boring project make it difficult to focus, that's completely normal. But if you find that you consistently can't complete projects—to the extent that you're missing deadlines or getting in trouble for it—you probably need medical attention. Or a new job.

See your doc if: You have severe problems with procrastination, wander aimlessly at work, and have a past history of poor work performance or switch jobs a few times a year. Adults with ADHD consistently have difficulties completing tasks and are often considered the “weak link” on the team. “They struggle with a constant feeling of underachievement and with self-esteem issues,” says Dr. Wilens. Across the board, they report more job changes, less tenure, and not as much enjoyment at work.

Too much stress

Stress takes a toll on concentration, says Dr. Wilens. “It competes with your cognitive centers—the areas in the brain that are responsible for quick, sharp thoughts—so being anxious or stressed drags focus down even further,” he says. Consider meditation: Researchers at the University of Wisconsin-Madison found that the relaxation technique can increase your ability to block out distractions. Another study, from researchers at UCLA, suggests that in adults with ADHD, meditation improves attention and eases symptoms of anxiety and depression.

See your doc if: You have other mood disorders related to stress, such as anxiety and depression, which often coincide with ADHD. Also, consider it if stress is making inattention or distraction worse, which, in turn, is negatively impacting your job, relationships, or academics. Taking this ADHD self-screening quiz, and discussing the results with your doctor, may help quantify how you're feeling.

Too little exercise

Mounting evidence suggests that regular exercise can keep your mind sharp and increase learning and memory capacity. It’s even more crucial in adults with ADHD, who battle mental restlessness. “My patients who exercise all report that they see improvement in attention,” says Dr. Wilens. Working up a sweat can also help you burn off the extra energy that causes you to feel fidgety, and it can help you sleep better at night.

See your doc if: You have a difficult time sitting still (like during a meeting or at your desk) and have an urge to constantly get up and move around the office. Or seek help if you’re self-medicating by exercising too much—say, two to three hours a day—just to keep your restlessness at bay.

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