Here's the typical scenario: pre-school boy bounces around, bounces off the walls, is hard to get to sleep at night, but as long as he can go outside and play he's generally okay ? a bit accident prone, but a BOY after all.

Then he goes to school. He can't sit still. He can't or won't follow instructions. He doesn't pay attention. He doesn't follow rules. He falls behind in class work and when he gets home from school, the last thing he wants to do is homework, so that becomes a fight. Teacher conferences are like dreaded encounters of the same magnitude as going to the dentist. Finally, someone says, "I think your son needs medication."

For what? Has he come down with a disease? Does he have an infection? You feel a bit offended and you ask the question, knowing already what you're going to hear. They respond, "We think Johnny has ADHD."

Attention Deficit/Hyperactivity Disorder (ADHD) has become one of the most common diagnoses in childhood, and now often is also diagnosed in adulthood. There are two types: Inattentive and Hyperactive.

There is no single way to diagnose ADHD. Many clinicians can get that done with a solid interview and reasonable history. You can add behavioural checklists, filled out by the parents and the teachers, so that you get reads on the child's behaviour in his or her two most common contexts of life, and that is usually done.

If diagnosing adult ADHD, one has to rely on the interview and history with a check to school records or history of school behaviour.

It's a good idea to get the opinion of other people who have known the adult when they were growing up, because often the person in question does not have helpful awareness of themselves in these matters. If it's a child, they couldn't care less, and if it's an adult who has begun to suspect they have ADHD, having read about it or heard about it somewhere, then the problem is that when they were a child, and even currently, they were not, and probably are not paying attention.

There are various theories about what resides at the core of ADHD ? that is, what causes it. There have been all kinds of remedies and treatments for it as well. Thankfully, we no longer put leaches on people for various maladies, and we no longer scramble the front of the brain with surgical instruments.

Generally, there are three focal points around which clusters of behaviour accrue: attention, impulsivity and organisation (these days often called executive function).

While it is necessary to make the general diagnosis, that is, to toggle from "yes" he's got it to "no" he doesn't, or the reverse, it is not actually helpful enough to leave it at that.

So our little boy has ADHD. There are no two boys or girls who behave, feel, and think identically in the way they do ADHD.

Further, there are no two families who are affected in the same exact way by a member having ADHD.

An analogy can be made to the difference, for instance, between intelligence and executive function. A very intelligent but disorganised person can appear to be stupid. When you give them the IQ test, they score high and people stand around scratching their heads. It's the executive dysfunction that is the root of the problem. Just so in ADHD.

A person may have various levels of attention and impulse control, but they will always have an executive dysfunction that is modifying those capacities. That is why, with increasing frequency, clinicians are relying on the neuropsychological testing that can provide a profile of executive strengths and weaknesses.

Such testing provides greater ability to create appropriate learning and treatment plans.

There is something else. Families are at risk when they include children with ADHD. Divorce is higher. Children with ADHD are also likely to have oppositional defiant disorder or a more serious version of that called conduct disorder. Depression and/or self esteem issues are common.

These conditions put severe strain on families, so it is always advisable for clinicians to consider the family system rather than to treat the child as an isolated person.