Theories 101: top ten theories of the causes of ADHD: Theory 2

In the last article we discussed the theory of lead causing ADHD. In this article we will discuss the theory of genetics causing ADHD. Just how big of a roll does genetics truly play when it comes to ADHD? Research studies have suggested that there may be a genetic link to this question.

There is a broad selection of "target genes" researchers are looking at; leading many researchers to believe that it is a combination of genetic and environmental factors. The genes in which different research studies are looking at include: Dopamine Transporter, Dopamine Receptors D2/D3, Dopamine Beta-Hydroxylase Monoamine Oxidase A, Dopamine Beta Hydroxylase  Gene (DBH Taqi), the 7-Repeat  Allele of the DRD4 Gene, the 10-Repeat Allele of the DAT1 Gene, Catecholamine-Methyl Transferase, Seratonin Transporter Promoter (SLC6A4), 5-Hydroxytryptamine 2A Receptor (5-HT2A), and 5-Hydroxytryptamine 1B Receptor (5-HTB1).

As you can see, researchers suspect multiple genes involved in causing a number of  ADHD cases. There are widely considered to be three subtypes of ADHD: Predominantly Inattentive Type, Hyperactive/Impulsive Type, Combined Type, and also Not Otherwise Specified Type. With all these different types of ADHD, there are sure to be just as many different causes. No two snowflakes are alike, and that's what ADHD is like. Researchers and physicians are making great strides at categorizing and treating ADHD.

Some of the studies that are being done include looking at twins and other family members of individuals diagnosed with ADHD as a basis for connecting ADHD to a genetic cause. Twin studies indicate a high probability of a genetic link to ADHD. There is a 75% chance of both twins having ADHD, when one of the twins is diagnosed with ADHD, even if they've been raised separately. Approximately 10% to 35% of children with ADHD have a relative with ADHD. Fathers who had ADHD when they were younger have a 1/3 chance of having a child with ADHD.

In the February 2010 edition of the Journal, Molecular Psychiatry, the National Human Genome Research Institute, of the National Institutes of Health in Bethesda, Maryland, reported that they had discovered a genetic variant on the Latrophilin 3 Gene (LPHN3) associated with different populations. "It is very intriguing that the same variant (SNP marker rs6551665) associated with susceptibility to ADHD is also associated with response to stimulant medication. This opens a window for the evaluation of molecular subtrates of ADHD and development of new drugs targeting new genes and brain pathways involved in ADHD, " said researcher M. Arcos-Burgos of the National Human Genome Research Institute at the National Institutes of Health in Bethesda, MD, and colleagues in Molecular Psychiatry.

Research on ADHD continues, but a genetic test for ADHD is not far off. Research will help determine what specific gene causes a specific subtype of ADHD, and what treatment works best. Researchers estimate between 70% to 80% of all ADHD cases are caused by genetics. They suspect environmental toxins as the culprit in the remaining number of individuals diagnosed with ADHD.

The National Institute of Health and The National Human Genome Research Institute is conducting a study on the Genetics of ADHD. They provide a $10 "Thank You" gift for everyone who participates in this important research study. This study could help improve treatment for ADHD patients in the future, and help improve the lives of millions of ADHD sufferers worldwide.

If you are interested in participating visit: NHGRI

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  You can download the PDF Application, and fax it to (301)480-7876, contact them at (301)402-8167, or email NHGRI with any questions or concerns.
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  Contact Maximilian Muenke, M.D., Senior Investigator and Chief, Medical Genetics Branch
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  Director, Medical Genetics Residency Training Program
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  Head, Human Development Section Building 10, Room 10c103
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  10 Center Drive, MSC 1852
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  Bethesda, MD 20892 1852        

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