Genetics and ADHD
Genetics in Human Affairs
GN 301-001 (8:00)
June 19, 2003
“I have neither given nor received unauthorized aid on this assignment.”
disorder that is evident in our societies’ children is a condition known
as Attention Deficit/Hyperactivity Disorder (also known as ADD or ADHD).
This disorder has two main types currently recognized by professionals
(physicians, counselors, psycho-evaluators, etc), inattentive and hyperactive-impulsive
The characteristics are noted in the Figure below.
Inattentive Type Characteristics:
Careless errors in schoolwork, work, or other activities
Difficulty sustaining attention in tasks or play
Difficulty listening to others
Often fails to follow instructions
Difficulty organizing tasks/activities
Dislikes/Avoids tasks that require sustained mental effort
Often looses things
Hyperactive-Impulsive Type Characteristics:
Inability to stay seated when expected/required
Running around/climbing when inappropriate
Difficulty playing quietly
Acts as if “driven by a motor”
Blurts out answers before questions have been completed
Difficulty awaiting turn
Often interrupts or intrudes on others
Figure: Characteristics of Inattentive Type and Hyperactive-Impulsive Type ADHD.
ADHD affects approximately 5-10% of children and adolescents and around 3% of adults. Affected individuals exhibit six or more symptoms of inattentive type, hyperactive-impulsive, or both. This disorder is also more common in males than in females (3-4:1), and can be accompanied with other social or mental maladies with varied frequencies such as Oppositional Defiant Disorder (ODD) (33%), Conduct Disorder (CD) (25%), anxiety disorders (25%), depressive disorders (20%), and learning disabilities (22%) (http://www.adhd.ucla.edu and Fisher et al., 2002). If undiagnosed, this disorder (along with any accompanied maladies) can place individuals at higher risk for social problems (substance abuse, any activity that may result in incarceration, etc), lower incomes, lower education levels, and increased pregnancies.
Many studies have been conducted to determine if the disorder is environmental, genetic, or both. Through these studies, researchers have determined that ADHD is for the most part a genetic problem based on the apparent redundant familial occurrences both in the nuclear family and in the extended family. The initial studies indicated that if a family has a child that has been diagnosed with ADHD, then there is 20-25% chance that a sibling will also show signs of the disorder. There also is a 15-40% chance that parents of ADHD children are affected with ADHD themselves. If one identical twin is diagnosed with ADHD, then the other twin has a 70-80% chance of being diagnosed also (both are genetic copies of one another; environmental factors may be the reason chance is not 100%), fraternal twins have a co-occurrence of 30-40% (they roughly share half the genetic makeup).
Studies have been conducted to try to determine if a single gene/allele or a multitude of genes/alleles are responsible for the phenotypic display of ADHD. The results of these studies indicate that there is no single major gene responsible for the emergence of the disorder, but that many genes interacting together may be the reason for the display of ADHD characteristics. As with all scientific studies, investigations into ADHD have lead to proof as well as disproof of the implicated genes/alleles.
Test results have revealed that individuals with a variation of their SNAP-25 gene have a 50% greater risk for ADHD than those without the variation; though it is not known what roll the gene plays in relation to ADHD (DeNoon et al., 2002). The SNAP-25 gene encodes for a protein essential for synaptic vesicle fusion and neurotransmitter release, and it is suspected that the variation of this gene alters neurological functions. This has been the indication in both familial studies and animal studies. Unfortunately the SNAP-25 gene only increases the risk for, rather than causing, ADHD. It is currently unknown exactly what role the SNAP-25 gene plays in ADHD (Brophy et al., 2002), but through continuous research a result may become evident.
Other genes implicated in the increased susceptibility of ADHD include those associated with serotonin transportation. It was discovered that a variation at a polymorphism in the serotonin transporter (specifically 5HTT and hSERT) directly influenced the inclination of risk for ADHD (Kent et al., 2002). Other studies that have recently been conducted also indicate an association between this variation and ADHD, but the data is still limited to a small test group. Until a larger testing group or more tests are conducted for a pooled analysis, the data will remain limited.
A genomewide study was conducted in which numerous families were studied in a multifactorial way in which both the test subjects’ and their families’ genes were analyzed (Fisher et al., 2002). This allowed the researchers to exclude the extraneous genes that were not producing the desired effect, ADHD. Researchers investigated the effects of 34 total genes spanning all 22 autosomes and the sex chromosome (X). Surprisingly, when evaluating the data, they found only 7 out of the 34 genes tested could be included to draw conclusions about ADHD. The 27 genes that were not used were excluded because they did not meet the required data range. The seven genes that remained for data analysis included those associated with interactions of dopamine (DRD5 (4p16.1), CALCYON (10q26.3)) and serotonin (HTR1A (5q12.3), HTR1B (6q14.1), HTR1E (6q15), 5HTT (17q11.2), and SNAP-25 (20p12.3)) with cells in the brain. Two of the strongest readings came from areas were a linkage with autism was known to occur. This study affirmed the speculation that there is not a single gene that causes ADHD, but that many genes work together to initiate symptoms. It is also noted that this was the first genomewide scan for genes affecting ADHD. Additional testing needs to be conducted in order to adequately answer the question of “what genes cause ADHD.”
Correspondence to chromosome 16p13 (in an area noted for autism) was indicated also in a study conducted by Smalley et al., 2002. This study indicated a linkage between autism and ADHD because the deficits found in both of these disorders are influenced by variations in the chromosome previously stated.
The continuation of research regarding genetics and ADHD is needed in order to educate the general public as well as to continuously inform the numerous professionals that are not directly involved with research. Through truthful and legitimate publications and broadcasts, the general public can begin to realize that ADHD is not an incurable disease or disability, but rather a slight disorder. Keeping that in mind, by simply restructuring person’s everyday activities and possibly medicating (though not always necessary), people with this disorder can function as normal and productive individuals. Once the disorder is realized, accommodations can be made to enable the individual to reach great heights such as entrepreneurs, doctors, lawyers, etc.
Thom Hartman explained the way persons with ADHD differ from "normal" individuals in an article he wrote in the July/August 1999 issue of Tikkun Magazine. In this article, he reveals a metaphor he uses to explain ADHD to children that are both affected and non-affected. Here is the metaphor taken from the article:
the Seventies, when I was Executive Director of a residential treatment
facility for disturbed children, I developed a metaphor to explain ADHD
to children, a metaphor which I subsequently published in 1991. The metaphor
was that hyperactive kids were actually "good hunters," whereas the very
steady, stable, classroom-capable kids were "good farmers." The hunters,
I suggested, would do great in the forest or battlefield: their constant
scanning ("distractibility") would ensure they wouldn't miss anything;
their ability to make instant decisions and to act on them ("impulsivity")
would guarantee they'd be able to react to high-stress and response-demanding
situations; and their love of stimulation ("need for high levels of stimulation")
would cause them to enjoy the hunting world in the first place. (At its
core, ADHD is diagnosed by evaluating the intensity and persistence of
these three behaviors.) I told these kids, however, that they needed to
learn the basic "farmer skills," because the world has been taken over
by the farmers. Even our schools were organized by the farmers: schools
let kids out in the summer so they can help bring in the crops. And factories
and cubicles, of course, are just an Industrial/Technological Age extension
of the skill-set useful in agriculture.
(Hartman, 1999, http://www.crforum.com/WhoseOrder.htm)
With this explanation, I began to realize that the two types of people are not worlds apart; they are only a little different in thinking. Not everyone understands that individuals with ADHD are competent; some believe ADHD is a sign of inferiority. Neo-Darwinists have been known to push their point of view by stating that people with ADHD are “less evolved” than people without the disorder. Some have even gone as far as saying that people with ADHD should not reproduce. This is absurd. I am an individual that has been diagnosed with ADHD – Inattentive type. I do not believe that I am inferior to others. I know I am not because I have the capability to do tasks and projects that others cannot. If we “hunters” do not reproduce, then the evolution of society will also begin to diminish because of a deletion in an entire way of thinking. I am bored with the idea of the “everyday routine,” I require a large amount of stimuli to function correctly. I cannot see why anyone would want to remove a characteristic like that.
The basis of “Darwin’s Theory” is survival of the fittest. Just because society has adjusted to the “9-5” mentality does not mean that the “farmers” are the fittest. There are certain places in society that a hunter-style mentality is needed. Without this mentality, positions for firefighters, police officers, or other high-risk jobs may go unfilled. It has been noted that individuals with characteristics of ADHD respond well in emergency situations. This is on the basis that individuals with this disorder (“hunters”) are pulling on primitive hunting skills. I believe this is true. As a firefighter, I love the thrill of a house fire (granted I am not a pyromaniac or a fire fanatic). The ability to work quickly, safely, and as a team is paramount when trying to save a life or property. These characteristics are almost second nature to most hunter-type individuals, and some people want to remove this form of thinking from our gene pool.
In helping individuals affected with ADHD adjust to the “farmer-style” world, the production of many different drugs have been introduced. The use of stimulants, such as Adderall and Ritalin, are extremely effective in focusing the individuals. Currently, I am prescribed Adderall and the difference for me has been unbelievable. I am actually able to sit in class and understand what is going on. Before, I struggled with nearly all classes because I was constantly daydreaming. The use of Adderall has allowed my brain to function normally, by allowing me to access the different areas more efficiently. There are numerous risks and side effects, both physically and socially.
Some of the physical side effects include constipation and/or cramps, diarrhea, depression, dizziness, dry mouth, insomnia, headache, high blood pressure, rapid heartbeat, loss of appetite, restlessness, tics, weight loss, and impotence (Bailey, date unknown). Other possible problems include drug interactions. Antihistamines, drugs that make urine more acidic, high blood pressure medications, lithium, major tranquilizers, Demerol, Urised, seizure medications, “Tricyclic” antidepressants, and especially MAO inhibitors should all be mentioned to the prescribing physician before consumption. Any foods that may lower the pH in the intestinal tract will also result in decreased absorption of the medication, thus limiting its effectiveness. As with any medication, until the effects of the medication is known, the operation of heavy machinery should be supervised. Because Adderall is a controlled substance, refills cannot be issued. Regular doctor visits are required for continuation of the treatment. Dietary supplements have also been tested to see if a non-medicinal treatment could be obtained, but the results obtained indicated the tested supplements were ineffective. Consumers of the supplements are not protected by the FDA, as are those whose treatment includes medication.
Social issues also arise with regard to ADHD and the medications taken to control its effects. Some issues are positive and some are negative. The implications of these issues are mainly based on that of public perception. If the public as a whole understood the characteristics of ADHD and the disorder was widely accepted, then “most” of the social issues would not exist. I say most because some issues need to remain for the security of the general public.
Legal discrimination is practiced, with regard to certain jobs, while individuals are on medication. This is a social issue that is fine as long as security or safety is a concern. An example of this is the inability to join the armed forces (specifically Navy) while under medicated treatment of ADHD (Bailey, 2001). This inability to enlist stands, as long medication is needed. If medication is not considered necessary, then an individual with ADHD is able to enlist after a period of six months after medication ceases. I believe this is a good practice. Anyone continuously under the influence of medications that affect brain activity and function is not generally wanted in the military. ADHD sufferers do not suffer from this penalty because, off medication, we exhibit “hunter” characteristics.
A negative social issue is the inadmissibility of ADHD in court. This is a terrible downfall. Preliminary studies suggested that around 70% of juvenile delinquents have ADHD and approximately 40% of males in medium security prison are affected (Bailey, 2001). This is a staggering number. I am not saying that anyone who commits a crime and also has ADHD should go unpunished. I am merely saying that as part of the rehabilitation process, society should include the diagnosis and treatment of ADHD. Studies have shown that when paroled offenders with ADHD were subjected to treatment (including medication, support groups, counseling, and medical treatment), the normal rate of recidivism was 53-58% after two years. This is much better than the 10% normal rate of the control group. This single study should not be the deciding factor on admissibility of ADHD in court, but it should be an indication that maybe further investigations should be made. Now do not get me wrong, if an individual breaks the law, they should be punished. However, if the public is better educated and ADHD does not become synonymous with “bad,” then maybe we as a society can assist in keeping these high-risk individuals from breaking the law in the first place.
If someone has ADHD and is having trouble at work, the federal government does assist the individual by way of the Americans with Disabilities Act. This enactment allows affected individuals the ability to receive certain accommodations in the workplace. It requires businesses to work with the individual to enable a more effective and efficient workplace. It does not mandate expensive or elaborate solutions. Examples of some accommodations include the restructuring of job duties (redistribute portions of the job to other employees), restructuring of deadlines or times when work is due, flexible work schedules or reducing work to part time, inclusion of audio or video tapes, access to tape recorders for meetings, color coding supplies (for filling, notes, important papers, etc), use of a computer, etc. All of these examples do not have to be met, but in working with the employer a median should be obtained.
an individual with ADHD – Inattentive type, I understand that going undiagnosed
for a large part of my life has allowed me to see both sides of the disorder.
The constant inability to focus and not understanding during my childhood
and now the mental clarity and order has given me the perspective I need
to recognize potential symptoms or problems in my children (when I have
them). I believe that instead of medications, I will first try lifestyle
and social modifications, with the help of a therapist, to deal with the
disorder. Only as a last resort do I want to subject my children to the
continuous medication procedures currently implemented. I also hope that
society as a whole can get past the notion that ADHD is a form of mental
retardation or mentally limiting problem. It clearly is not. It is an altered
way of thinking, a genetic variation that maintains everyone’s belief
Brophy K, Hawi Z, Kirley A, Fitzgerald M, Gill M. Synaptosomal-associated protein 25 (SNAP-25) and attention deficit hyperactivity disorder (ADHD): evidence of linkage and association in the Irish population. Mol Psychiatry. 2002;7(8):913-7. PMID: 12232787 [PubMed - indexed for MEDLINE]
DeNoon, Daniel. ADHD Gene Discovered: Attention Deficit More Common in Kids with ‘SNAP-25’Mutation. September 24, 2002. WebMD Medical News. http://content.health.msn.com/content/article/50/40533.htm
Fisher SE, Francks C, McCracken JT, McGough JJ, Marlow AJ, MacPhie IL, Newbury DF, Crawford LR, Palmer CG, Woodward JA, Del'Homme M, Cantwell DP, Nelson SF, Monaco AP, Smalley SL. A Genomewide Scan for Loci Involved in Attention-Deficit/Hyperactivity Disorder. Am J Hum Genet. 2002 May;70(5):1183-96. Epub 2002 Mar 28. PMID: 11923911 [PubMed - indexed for MEDLINE]
Kent L, Doerry U, Hardy E, Parmar R, Gingell K, Hawi Z, Kirley A, Lowe N, Fitzgerald M, Gill M, Craddock N. Evidence that variation at the serotonin transporter gene influences susceptibility to attention deficit hyperactivity disorder (ADHD): analysis and pooled analysis. Mol Psychiatry. 2002;7(8):908-12. PMID: 12232786 [PubMed - indexed for MEDLINE]
Smalley SL, Kustanovich V, Minassian SL, Stone JL, Ogdie MN, McGough JJ, McCracken JT, MacPhie IL, Francks C, Fisher SE, Cantor RM, Monaco AP, Nelson SF. Genetic Linkage of Attention-Deficit/Hyperactivity Disorder on Chromosome 16p13, in a Region Implicated in Autism. Am J Hum Genet. 2002 Oct;71(4):959-63. Epub 2002 Aug 14. PMID: 12187510 [PubMed - indexed for MEDLINE]
University of California Los Angeles. Center for Neurobehavioral Genetics. Attention Deficit Hyperactivity Disorder (2003). http://www.adhd.ucla.edu
About.com (no author given). 2003. ADHD in the Justice System: Should impulsiveness be taken into consideration in the court system?. July 29, 2001. http://add.miningco.com/library/weekly/aa072901a.htm
Bailey, Eileen. ADHD in the Military: Ritalin is not welcome in the armed forces. About.com. September 16, 2001. http://add.miningco.com/library/weekly/aa091601a.htm
Bailey, Eileen. ADHD Medication Fact Sheet: Adderall. About.com. No Date Specified. http://add.miningco.com/library/bladderall.htm
Bailey, Eileen. ADD/ADHD in the Workplace: Accommodations. About.com. December 12, 2002. http://add.miningco.com/library/weekly/aa111202a.htm
Barclay, Laurie. Dietary Supplement Not Effective in Treating ADHD. August 16, 2001. WebMD Medical News. http://content.health.msn.com/content/article/34/1728_86839.htm
Hartman, Thom. Whose Order is Being Disordered by ADHD. Tikkun Magazine, July/August 1999. Volume 14 Number 4. http://www.crforum.com/WhoseOrder.htm