In the intervening years science has come round to Hafer's viewpoint; it is now widely accepted that ADD is the result of neurochemical imbalances which affect the forebrain's ability to process information and to restrain inappropriate impulses which originate in older – in terms of evolution - areas of the brain. In the past, studies have shown that brain scans can detect structural differences in ADHD sufferers' brains, as well as abnormalities in brain activity, and some scientists came to suspect that defects in genes relating to the brain chemical dopamine probably are involved.

Impressive evidence in support of this viewpoint can be derived from recent research conducted at the Massachusetts General Hospital in Boston. Scientists there have developed a brain scan which can detect the amounts of dopamine transporters present and active in the brain. Dopamine is associated with movement, thought, motivation and pleasure. One brain cell signals another by squirting dopamine. Then the first cell mops up the released chemical with a structure called a dopamine transporter.

The researchers scanned the brains of six adults diagnosed with ADHD and 30 healthy people of the same age after injecting both groups with a chemical agent that attaches to the dopamine transporter. The ADHD sufferers had 70 per cent more dopamine transporters than their healthy counterparts. The scientists could not tell, however, whether that was a cause or an effect of the disorder.

"The increased number could either mean not enough dopamine is floating around the system or that too much is being produced", said one of the researchers, Dr. Bertha Madras, a professor of psychobiology at Harvard Medical School.

"It's very early days, but if all hyperactive adults and children show a 70 per cent increase above normal in this test, I think it would de facto be considered a diagnostic," Madras said. This study, conducted at Massachusetts General Hospital in Boston and published in The Lancet medical journal, is the first to show a measurable biochemical abnormality in the brains of people with ADD.

The diagnosis of ADD/ADHD is currently based on observed behaviour and some experts believe it is a highly subjective diagnosis, sometimes little more than an educated guess. It is also argued that the condition is being over-diagnosed in the US and in Australia. Concern was expressed recently in the state of Western Australia over the fact that prescriptions to children of stimulants, such as Ritalin and Dexamphetamine, have doubled in the last three years. On the other hand, other professionals argue that far more children are evidencing at school many or most of the classic symptoms of ADD than are actually diagnosed with the condition.

This Boston research may lead to scans which can determine accurately and objectively who has ADD and who has not, and to what degree individual sufferers' brains are incapacitated by the condition. Hafer has argued for a long time that ADD is not simply a condition that one has or does not have but a condition which affects up to maybe fifty percent of the population to varying degrees, from imperceptible to extremely severe. Such a scan could also make it possible to measure accurately the effectiveness of various treatment and management regimes, since 'before' and 'after' treatment scans would presumably reveal a reduction in biochemical abnormality which would parallel improvements in behaviour in cases where a given treatment regime appeared to be successful.

Reference: "Education Review", Vol 4 No 1, February/March 2000, p 6 (published by APN Educational Media Pty Ltd and the Australian College of Education, ISSN 1329-6329)