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Neuropsychiatric Genetics Research Group
Attention-Deficit/Hyperactivity Disorder

Attention Deficit Hyperactivity Disorder (ADHD) affects approximately 3-6 % of all children. Onset is prior to seven years of age and generally persists throughout childhood but often beyond into adolescence and adulthood. It is a biological, brain-based condition which results in two primary areas of impairment - attention and impulsive-hyperactive. These in turn cause educational, family and social problems.

We have found evidence that genetic variation at the Dopamine transporter gene possibly contributes in a small way to the cause of ADHD. We have also found evidence that two further genes may be involved. These genes are known as Dopamine beta hydroxylase, which is a gene coding for a naturally occurring enzyme, which is necessary to break down the neurotransmitter dopamine in the brain after its use. The second gene we have identified as potentially playing some role, is the Dopamine 5 receptor (the fifth subtype in a family of five Dopamine receptors). Our studies suggest that subtle DNA sequence difference (inherited differences) at these genes may contribute to risk, in addition to risk caused by the Dopamine transporter. Over the past two years we have taken advantage of significant advances in genetic technology platforms. In one of our studies (the IMAGE project) this has enabled “whole genome” analysis of common variation in our DNA sequence. Our strategy examines how DNA is passed on from parents to their child with ADHD. We have recently completed a study, as part of the GAIN Initiative to examine over 600,000 DNA markers in nearly 1000 mothers, fathers and their children who have ADHD. Many biologically plausible novel genes and pathways have been identified from these studies that can be further examined in individuals with ADHD.

The finding that several genes are possibly involved is very much what we expected given that ADHD is quite common and yet does not follow a clear inheritance pattern.

This pattern is also seen for many other conditions such as asthma, diabetes and many other common disorders, which are at least partially inherited. It indicates that it is likely that many genes of small effect combine to contribute to risk, but in any individual case, it may be impossible to determine which genes are involved.

This research will involve a member of the research team carrying out a clinical interview with a parent of each child with ADHD. The interview is confidential and will take approximately an hour, or alternatively, it could be divided into two sessions. We will also need to obtain a small blood sample from the child and from both mother and father.

There are a number of studies into ADHD on-going in the group at the moment:

  1. On-going ADHD Genetics Study with Dr Ziarah Hawi and Dr Naomi Lowe
  2. Deficits in attention and executive function in relation to genotype Study with Prof. Michael Gill, Prof. Ian Robertson, Dr Katherine Johnson and Dr Wouter Braet
  3. International Multi-center ADHD Genetics Project (IMAGE) with Dr. Aisling Mulligan and Louise Butler
  4. STAR Study - A prospective study of the clinical genetics of methylphenidate response in children with ADHD with Drs. Aiveen Kirley, Edwina Barry, Marie Cox

For more information

Phone or email:
Louise Butler Tel. (01) 896 2465
Aisling Mulligan Tel. (01) 896 2465

Last updated 21 September 2016 by School Web Administrator.