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What is ADHD?

Despite all the media hype about ADHD, it is not new. In 1902 it was described as "defective moral control". We may laugh at the name but the symptoms described were very similar to what we now identify as ADHD. It went through many permutations of name including "minimal brain damage" and "minimal brain dysfunction", all the absence of any evidence of brain disturbance. But there is still disagreement over the definition.

Differences in the definition of ADHD

There is such variation between countries and over time in the definition of ADHD that it is no wonder people are confused. A brief history lesson is needed. The USA and Australia have gone mainly with the DSM (Diagnostic and Statistical Manual) classification developed by US psychiatrists to ensure people were diagnosing behavioural and psychiatric problems in the same way. In 1987, DSM-III-R recognised just one form of ADHD, where children had to have 8 out of 14 attention and activity problems. Many clinicians felt this was not right and that not all children with ADHD were the same. So DSM-IV came out in 1994 with three types of ADHD, a purely Inattentive type, a purely Hyperactive/Impulsive type and Combined type who had both sorts of symptoms. The first had to have six of the nine Inattentive symptoms, the second six of the nine Hyperactive/Impulsive symptoms and the third six of each.

The diagnosis was not just based on having symptoms but on having these to the extent that quality of life was impaired in at least two situations (home, school, etc) At the same time, the sub-division of diagnoses recognised the three types have different patterns of comorbidity, that is of problems with reading disability, clumsiness etc that justify the distinction.

Europe has gone much more with the ICD-10 classification, the International Classification of Diseases which is a more extensive classification system that covers not just behavioural problems but also physical ailments. Without being too precise, to be diagnosed with ADHD in this system one must have both Inattention and Hyperactivity and Impulsivity symptoms (so it is more like the DSM-IV combined type) and problems must be identified by two sources (for example, teachers AND parents). Thus this classification is much more restricted and restrictive.

So now you know psychologists and psychiatrists are only just starting to converge on a definition of this problem. What does it mean for the family and the school?

• the DSM-IV diagnosis means there will be many children who have attention problems that are not being recognised. They have none of the hyperactive signs that are so often shown by the media as being key to ADHD- hyperactive children make better footage than inattentive ones! In fact the purely Inattentive type is the most common in all population studies and the purely Hyperactive/Impulsive the least common, with the Combined type somewhere in between.
  
  
• but surely all children (and many adults) have attention and activity problems? In 1997 we showed that the symptoms of ADHD were a continuum throughout the population. Yes, we all have some symptoms but few of us have so many and have them to the extent they are so disruptive that the label of ADHD is warranted. It is where to draw the line that causes the controversy. Yet we accept such cutoffs in everything from the diagnosis of intellectual disability or high blood pressure to speed limits.
  
  
• think comorbidity. It may not be ADHD but all the other things that can accompany it, such as conduct disorder, a history of reading problems plus intervention and clumsiness that make this such a problem for the family. Indeed we have been developing a concept of DARC, disorders of Attention, Reading and Co-ordination, which identifies how commonly these three problems occur. In some ways this is reassuring to families. There may be skepticism about the diagnosis of ADHD but less often about the inability to stand on one leg or catch a ball. These are some data from our Australian Twin ADHD Project that deal more generally with conditions that may co-occur with ADHD.

What is conduct disorder? It is not just naughtiness. "We asked the mother of young MZ twin girls if they were ever cruel to animals (one of the routine questions). After a pause, she said, one had sat on the cat while the other cut off its ears….."

Actually conduct disorder is no more common in multiples than in singletons, even though it has some association with ADHD.

Separation Anxiety refers to the "clinginess" that most children show at some time and again it is only when this becomes disruptive that it is an issue. It may be a little more common in young multiples as they try to find ways of getting parental attention. It may also be more common in all young people with ADHD as they rely more on their parents. As explained below, ADHD often means you have few friends and thus you may not want to be away from the parents who are the ones you can rely on.

These results illustrate how comorbidity differentiates the subtypes:

• the Hyperactive/Impulsive subtype has no more problems with speech or reading than the twins without ADHD but more Conduct Disorder and Separation Anxiety
  
  
• the Inattentive and Combined types have higher rates of speech intervention and almost half have had reading intervention. We now know they were more likely also to have co-ordination problems. The Combined type has much more Conduct Disorder than the others.