Study raises questions about diagnosis and medical treatment of ADHD

UCLA Study questions long-term effectiveness of ADHD treatment

New ways of thinking about the disorder are needed, say researchers.

A new UCLA study shows that only about half of children diagnosed with attention deficit hyperactivity disorder, or ADHD, have the cognitive defects typically associated with the disease.

The study also found that in populations where medication is rarely prescribed to treat ADHD, the prevalence and symptoms of the disorder are roughly equivalent to populations in which medication is widely used.

The results of the first large longitudinal study of adolescents and ADHD, conducted in the northern Finnish population, were published in several articles in a special section of the Journal of the American Academy of Child and Adolescent Psychiatry published in December.

Among the alternative methods that have proven successful, the rehabilitation of listening posture according to A. Tomatis shows encouraging results. In some cases, the child is able to stop taking medication, and his or her school results improve on a long-term basis.

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ADHD is a common chronic behavioural disorder characterised by inattention, hyperactivity and impulsivity that is thought to affect 5-10% of school-aged children worldwide.

In adolescence, ADHD is generally associated with cognitive deficits, particularly with working memory and inhibition, which have been linked to overall intelligence and academic achievement, according to Susan Smalley, professor of psychiatry at UCLA. Interestingly, the study found that these deficits are present in only about half of the adolescents diagnosed with ADHD.

Part of the explanation may lie in the common method of diagnosing the disorder. ADHD is an extreme on a normal continuum of behaviour that varies in the population, just like height, weight or IQ. Its diagnosis, and therefore its prevalence, is defined by health professionals "drawing the line" on this continuum, based on symptom severity and overall impairment. However, the study showed that children with cognitive deficits are not more prone to increased levels of inattention or hyperactivity than other children diagnosed with ADHD, suggesting that behavioural rating scales are not sensitive enough to differentiate the two groups.

Additional psychological testing is recommended to confirm the presence of cognitive impairment.

The researchers also found surprising results regarding the effectiveness of medicine in treating ADHD. Unlike children in the US, young people in northern Finland are rarely treated with ADHD medication, but the appearance of the disorder - its prevalence, symptoms, psychiatric comorbidity and cognition - is relatively similar to that in the US where medication is widely used. The researchers point out that this raises important questions about the effectiveness of current ADHD treatments for the long-term problems of the disorder.

"We know that medications are very effective in the short term," said Smalley, author or co-author of each of the papers. "But the study raises important questions about the long-term effectiveness of ADHD treatment: we have two different cultures and two different approaches to treatment, but in adolescence there is little difference in the presentation and problems associated with ADHD. "

Other findings from this large study include:

  • Further confirmation that ADHD symptoms change with age: hyperactivity and impulsivity decrease with age, while inattention increasingly predominates. In fact, about two-thirds of children with ADHD continue to show significant levels of inattention and impairment into adolescence.
  • ADHD is associated with increased rates of other psychiatric problems. The most prominent in adolescence are depression; anxiety; oppositional behaviours, such as arguing, losing one's temper and being easily upset; and leading disorders such as vandalism and truancy. Surprisingly, post-traumatic stress disorder is significantly elevated in adolescents with ADHD compared to non-ADHD youth. The prevalence of these co-occurring disorders is comparable to that observed in other ADHD populations worldwide.
  • Two genes, called DBH and DRD2, involved in the regulation of dopamine - a neurotransmitter involved in attention, motivation and emotion - have also been associated with ADHD in the northern Finnish population. Although the researchers involved say that they probably account for very little of the genetic variation underlying ADHD, the findings provide further support for the involvement of the dopamine pathway in the etiology of the disease.

"This set of papers highlights the need to engage in new ways of thinking about ADHD," said Smalley, who is also a member of the Center for Neurobehavioral Genetics at UCLA. "Certainly, it is a valid disorder, but ADHD predispositions are normal in attention and activity, just like diabetes and glucose tolerance, or dyslexia and reading disability.

"The continuing nature of ADHD liability requires that we look more carefully at what environmental pressures can lead to impairments, rather than expanding our diagnostic classifications further," she said.

The study began in 1986, when researchers from Imperial College London and the University of Oulu in Finland began studying 9,432 children in northern Finland. They followed the children from early fetal development to adolescence (ages 16-18). The UCLA researchers then joined forces to examine ADHD behaviours in adolescents, using a standard screening survey and diagnostic criteria. Among the 6,622 survey respondents, a subset of 457 probable cases and controls were assessed for ADHD and other psychiatric disorders. The estimated prevalence of ADHD among these adolescents was 8.5%, with a male-to-female ratio of 5.7 to 1.

In addition to Smalley, UCLA researchers involved in the study included Lorie A. Humphrey, Sandra K. Loo, James T. McCracken, James J. McGough and Stanley F. Nelson.

Mark Wheeler, 22 January 2008