I had just completed my evaluation of 11-year-old Timmy. His parents had brought him to me because of behavior problems and his teacher?s concern that Timmy was underachieving in school. I determined that Timmy had attention deficit hyperactivity disorder, often referred to as ADHD or ADD. After I inform families of my diagnosis, one frequent remark parents make is, "We don?t understand how he has attention deficit disorder; he can pay attention when he wants to." Timmy?s parents then gave me examples about his being able to sit for hours playing computer games or watching television. "But he just won?t sit and do his homework." This is a typical remark from parents. From a parent?s point of view, their son or daughter doesn?t seem to have a disorder; they see a child who just doesn?t seem to care. As a child psychiatrist, I welcome parents? questions and comments. Their questions give me an opportunity to educate them as to what ADHD is. Lots of people don?t really understand this disorder. But the better they do understand ADHD, the more likely they will be to make appropriate decisions on how to guide a child like Timmy. The Search for Stimulation One of the problems in understanding attention deficit hyperactivity disorder is the limitations of its name. It?s a pretty good name, better than the earlier names we used, such as "minimal brain dysfunction" and "hyperkinetic syndrome." Using attention deficit hyperactivity disorder is better because it reaches closer to the core of the disorder: the difficulty in sustaining attention to tasks, rather than simply the hyperactivity. But even this name falls short in helping families understand the disorder, as in Timmy?s case. Saying Timmy has attention deficit hyperactivity disorder sounds like Timmy has two problems: an inability to pay attention and hyperactivity. Let?s examine the term, taking on the second part of it first. Hyperactivity is just one symptom. And as with any disorder people don?t necessarily have all the symptoms. Timmy, for example, is not hyperactive. Secondly, regarding "attention deficit." Timmy?s parents do not see their child as having an attention problem, but rather an attitude problem. To his parents, Timmy seems not to care. If he only had a better attitude, they reason, he would do his work and he would not get into so much trouble. Timmy?s parents were certain he could pay attention if he wanted to. If I was in charge of renaming ADHD?and I?m not?I would call it the "search for stimulation disorder." To explain this, let?s look at the problem of Timmy?s attention. Timmy has difficulty sticking to tasks such as homework or other relatively less interesting chores, such as cleaning up his room. To Timmy?s parents, it wasn?t that he couldn?t do his chores, but that he just didn?t want to do them. Timmy?s parents are partially right. Timmy can do things that he is interested in, but he has trouble with jobs that require more sustained effort. It?s not because he doesn?t care; it?s because, more than most other people, he needs to find something interesting for it to hold his attention. Timmy searches for stimulation. That often gets him into trouble because he doesn?t pay attention when he?s supposed to. He turns to look out of the classroom window when he should be listening to the teacher. He gets up out of his seat during the middle of a lesson. He annoys other children when they are trying to listen or do their work. Although medical scientists do not know exactly what causes ADHD, I can tell you what I think it is, just as I explained it to Timmy?s parents. What Causes ADHD? Most child psychiatrists, including myself, do not believe the root cause of ADHD is psychological. We believe an abnormality in the body?s nervous system produces the disorder. As I told Timmy?s parents. This is only a hypothesis, and no one really knows what causes ADHD. But the nervous system hypothesis has considerable explanatory value, and I believe something like it does operate in ADHD. I describe ADHD as a kind of barrier to the nervous system?an invisible shield that prevents normal levels of stimulation from getting through. It is as if Timmy had a thick layer around his nervous system: normal levels of stimulation don?t penetrate it. Just as nature hates a vacuum, so, too, the nervous system hates sensory deprivation. So if Timmy doesn?t get stimulation, he will seek it out. This would explain Timmy?s excessive need or, perhaps better put, his thirst for any stimulating information or event. He looks out the classroom window not because he?s lazy or wants to annoy his teacher or his parents but because he?s looking for something to hold his interest. He simply finds school work and chores too boring. Timmy wants to do well. He wants to make his parents proud of him. But he just can?t seem to do this, because of his excessive need for stimulation. In class, Timmy fidgets and is easily distracted. He can?t maintain focused attention on what is being taught. However, if the teacher increases the level of stimulation, Timmy can more easily pay attention. The teacher can get his attention in a variety of ways. She can teach in a more dramatic or dynamic manner. She can sit him in the front row and engage him with more frequent eye contact or by directing questions directly to him. Yelling will certainly get his attention, but I, of course, I don?t recommend this. Making the Diagnosis Not all children or adults with inattention have ADHD. For example, inattention can result from low IQ or when kids with high intelligence are placed in academically unchallenging environments. Some rebellious children resist tasks that require self-application simply because of an unwillingness to conform to others? demands. Certain medications (for example, bronchodilators for asthma or isoniazid for tuberculosis) can cause inattention, hyperactivity, or impulsivity.