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Curtin University of Technology
Twins and Multiples

Attention Deficit Hyperactivity Disorder (ADHD)

ADHD is now often being overdiagnosed, or wrongly diagnosed, so that some children who actually need help are not getting it. In 1996 we demonstrated that ADHD was slightly more common in twins than in their siblings, although no other behavioural problems are. This plus the association with reading problems makes it an important topic to raise. There is much controversy over ADHD and both causes and treatments. Here we follow the 1995 guidelines of the National Health and Medical Research Council of Australia, and do not deal with some of the "alternative" explanations and interventions such as diet. These may have a role for a minority of children, but large-scale studies in Victoria, Australia show this really is a small percentage of those diagnosed.

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 in 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?

ADHD category Reading Therapy Speech Therapy Conduct Disorder Separation Anxiety
No Diagnosis
Hyperactivity - Impulsivity
Combined Type

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: