It’s hard for Tony to stay focused. He is easily distracted and has difficulty getting and staying organized. Often his choices look impulsive. Restlessness is his middle name. Nonetheless, he’s a highly successful attorney. He just figures he’s a classic Type A personality who always has to be working very hard and disciplining himself to get things done.

His new girlfriend isn’t so sure. She thinks she could fall in love with him but he’s driving her crazy. “Why can’t he even sit through a movie without fidgeting or getting up to get a snack or to straighten something he notices is out of order, or just to walk around the couch?” She wishes he would just settle down! Please! She’s gone on the web to see if she can make sense of his distractibility and agitation. Aha! The symptom list for ADHD is a perfect match. “Maybe you should see your doctor for some medicine,” she told him. “Maybe then we would be able to have a quiet dinner out. It would be wonderful to have a conversation that stayed on topic for more than a few minutes.”

That was six months ago. Much has happened since. Tony was fortunate. He liked his girlfriend enough to want to please her, so he did ask his doctor whether something could be done to help him be more relaxed. Rather than jump to conclusions based on Tony’s report of his behaviors and his girlfriend’s certainty that he had ADHD, his doctor took the opportunity to do a long-overdue physical exam and to run some tests. The result? A diagnosis of thyroid hormone resistance. Appropriate treatment followed.

Oh, Tony will always take pride in being a bit driven. But he is now able to concentrate. He doesn’t lose his keys or misplace files every day. Best of all, he is able to pay attention to his girlfriend — and his clients — in a way that they experience as more respectful and caring.

Adult ADHD is often underdiagnosed. Although as many as 8 million American adults have it, it has often been missed. For many years, it was thought that children with ADHD outgrew it. Sometimes being unable to control one’s behavior or focus one’s thoughts was seen as an issue of immaturity or refusal to grow up and get with the program. And sometimes the symptoms were seen simply as an eccentric and scattered personality type.

Over the last decade, though, the public has become more aware that ADHD often is carried into adulthood, and medical and mental health professionals have become more sophisticated in making the diagnosis. The result has been the classic pendulum swing, with patients coming in having diagnosed themselves with ADHD and requesting (sometimes even demanding) Adderall or Ritalin to help manage it. Doctors who are under pressure to see four patients an hour don’t always take the time to do a thorough workup and sometimes acquiesce rather than argue with an insistent patient. A consequence is that at least some of the time, people are being treated for ADHD while a perhaps more serious condition goes unrecognized.

The truth is that there are at least a dozen disorders and diseases that share the same symptoms as ADHD. Sleep disorders, mental illnesses like anxiety, depression, and bipolar disorder, neurological conditions like absence seizures or a brain tumor, and even allergies can account for hyperactivity, difficulties with short-term memory, and lack of focus. Medications, whether prescribed or over-the-counter, can produce unexpected or unrecognized side effects of agitation or problems with concentration. And sometimes what looks like ADHD is the way a person is compensating for undiagnosed learning disabilities.

If you or someone you care about passes an online test for ADHD, by all means take the symptom list seriously. But don’t accept the diagnosis as fact without first consulting your doctor to determine whether there is a medical or medication-related explanation. Proper diagnosis is the only way to ensure that symptoms get properly treated.