ADHD: Risk Factors and Preventative Care
Attention deficit hyperactivity disorder, also known as ADHD, is one of the most common neurodevelopmental childhood disorders in the world. There are three subtypes of ADHD; predominantly hyperactive/impulsive type, predominantly inattentive type, and combined type. Although ADHD can persist throughout a person’s life, the focus of this paper will be on children because research pertaining to this disorder in children is much more established and the DSM-5 standards require symptoms to be present prior to the age of twelve. The prevalence of ADHD will be discussed, along with clear methods on how to recognize, diagnose, and treat this disorder. Research into the risk factors and causes will also be discussed, as well as controversy surrounding these studies.
The average age of the onset of ADHD is at seven years old. Studies also show that boys are four times more likely to develop ADHD than girls. A significant amount of research has been done pertaining to sex and age. The objective of one study in particular was to examine the age and gender differences in ADHD in a large community-based sample. The sample was divided by age into three groups; children (7-12 yrs.), adolescents (13-17 yrs.), and young adults (18-29 yrs.). The prevalence was calculated for the different subtypes as well as the male to female prevalence ratios. The overall prevalence was found to be 9.2% (11.6% in children, 9.7% in adolescents, and 6.4% in adults). However, it was found that the difference was only statistically significant in children.1
Throughout the world, ADHD has increased in diagnosis rates over time. In 2010, the rate of diagnosis was 3.1%, jumping up from 2.5% in 2001. While this jump may seem small, it is much more visible when you break it down by race. From 2001-2010 the rates of diagnosis had increased in Whites from 4.7% to 5.6%, Blacks from 2.6% to 4.1%, and Hispanics from 1.7% to 2.5%.2 ADHD, overall, is very prevalent throughout the world; about 5% of the world’s population has ADHD. High prevalence rates are found in Western Europe and Latin America in addition to the United States.3
When talking about ADHD, it is important to see the overall diagnosis rates in the United States, as well as data stratified by ethnic groups to see if there may be a correlation between the two. Of all the children diagnosed with ADHD, 54% are white, 14% are black, and 25% are Hispanic. These diagnosis statistics may also be based on socioeconomic factors as well. A study suggests that although children who are black have lower diagnosis rates, they have significantly higher likelihood of displaying ADHD symptomatology.4 This could also be due to any inheritance factors of ADHD.
Unlike many diseases that can be easily diagnosed through medical testing and various scans, ADHD is a mental disorder that isn’t linked to a specific gene or foreign particle, at least not yet, and there are no distinguishing differences that appear on a brain scan. Hundreds of studies have been done trying to establish risk factors that may increase a child’s chances of developing ADHD, but there is still no single test that can diagnose a child as having ADHD.
Genetics are believed to play a large role as a cause of ADHD as studies have shown that ADHD runs in families. Studies have been done across the world using genome linkage scans to try to identify certain genes that may cause higher risk of development of ADHD.5 Knowing the genes involved may one day lead to higher prevention and better treatment. Some of the current genes that researchers are targeting are discussed elsewhere in this article. Another viable genetic link that has scientific support is the association with a gene causing thinner brain tissue in children, especially in the areas that deal with attention. The research showed that as the child grew up, the brain developed normal thickness and the ADHD symptoms that were present as a child improved.6 This would explain why many children outgrow ADHD before they reach adulthood. Other genetic variations that are not inherited, such as duplication or mutation of the DNA segments have also been studied and suggest a possible role in this disorder.
Certain environmental factors are also believed to increase risk of ADHD in children. One of the most studied correlations is that of prenatal exposure to ADHD. In a study done by Nomura et al at Queens College in New York, they found that mothers who smoked during pregnancy put their children at increased risk for ADHD. In households where both the mother and father smoke, while the paternal use was not associated with increased risk, his use influenced that of the mother, so intervention was suggested for both7. Other negative prenatal exposures include alcohol, illicit drugs, antihypertensive drugs, antidepressants, and caffeine. Links to premature birth, low birth weight, maternal obesity, and maternal stress have also been studied. None have been shown to be causes, but all have been deemed possible risk factors given the results done in a study by Froehlich et al. Another environmental link is through high metal and chemical exposures. Lead, manganese, mercury, organochlorines, organophosphate pesticides, and phthalates were all included in the study by Froehlich, with lead having the most convincing evidence.8 Metals naturally found in the body like zinc, iron, and copper were also evaluated.
Inconclusive and inconsistent findings have also been found with respect to diet, brain injuries, parenting, and social factors. Refined sugar and food additives are being looked at as risk factors, but more research discounts these findings rather than supporting them. As far as brain injuries go, the sample size of children that have traumatic brain injuries is very small, so this aspect is hard to study. Early institutionalization or a traumatic event may lead to altered development, which may lead to ADHD. Any of these may make symptoms worse, but there is not enough evidence to suggest any of them are a major cause of ADHD.
Biology of Disease
It is important to acknowledge that ADHD is not a single pathophysiological entity and has a complex etiology. There has been several studies that identify various genes that may be linked to ADHD. Geneticists have also proven correlation to chromosomal deletions and duplications within the nucleotides of DNA for ADHD patients.7 There are also comorbid cases of ADHD in which patients later or simultaneously develop more severe disorders such as Turner syndrome, Williams syndrome, DiGeorge syndrome, and other mental health problems.
Research suggests that ADHD is a heritable condition, but molecular genetics studies show that the genetic makeup of ADHD is very complex. Genome wide linkage and associative scans have been conducted, however, none of the findings have been conclusive enough to definitively say that genes are a major cause. Twin studies were done so that genes and environmental factors could be separated and studied without confounding factors. In a genome wide linkage scan, many DNA markers across the genome are examined to see if any chromosomal regions are shared more often than expected among ADHD family members.5 The International Medicine ADHD Gene (IMAGE) project analyzed 51 different genes believed to be involved in ADHD. Families were recruited using an ADHD combined-type child proband who had one full sibling and one biological parent that were available for study. A high-density single nucleotide polymorphism (SNP) map was made for the genes that were involved in the regulation of neurotransmitter pathways by tagging these SNPs within the known functional regions. Some of the specific genes that were looked at include the 148-bp allele and the dopamine transporter gene (DAT, SLC6A3), which is the gene affected by stimulant medications taken by ADHD patients to give them therapeutic effect. Meta-analysis of 14 independent family based studies found the 148-bp allele to be significant, but on the opposite side of the distribution. This allele was found to lead to lower hyperactivity scores. Data from the DAT gene was just barely significant, which lead researchers to declare them inconclusive. Ongoing and more extensive research will be needed to understand the molecular genetics of ADHD and any relationship it can have relating to inheritance.9
Environmental factors are also believed to play an important role in the pathogenesis of ADHD. Prenatal factors are associated with maternal lifestyle during pregnancy. For example, children exposed to alcohol prenatally are more likely to be hyperactive and disruptive because the alcohol can induce brain structural anomalies. Studies support a dose-response relationship between maternal drinking during pregnancy and ADHD. There have been some research on postnatal factors such as malnutrition and dietary deficiency that can contribute to a child having ADHD, but further evidence is needed to establish this study.7
Inattention and hyperactivity are key behaviors in children with ADHD. However, it is common for all children to display these characteristics sometimes, which makes diagnosis that much more difficult. Inattention consists of behaviors like being easily distracted, having trouble focusing, and losing interest quickly. Hyperactivity includes fidgeting or squirming in their seats, nonstop talking, and impatience. Each of these can be seen in a normal child, but for a child with ADHD, they are more severe than average.
To be diagnosed with ADHD, a licensed professional must gather information about the child’s behavior and environment. Typically, a child needs to have symptoms for at least six months and at a higher degree than a normal child. The health professional can be a family pediatrician or a mental health specialist. It is important not to jump to conclusions and assume that a child has ADHD. The health professional will look into the child’s medical records for clues. They also ask questions of the parents to try to rule other possibilities for the symptoms. Teachers, coaches, babysitters, and other adults that know the child may also be contacted. The specialist will evaluate the child’s reaction and behavior in certain situations. If the child then meets the criteria for ADHD, he/she will be officially diagnosed. The current standard used by mental health professionals across the country is the American Psychiatric Association’s Diagnostic and Statistical Manual, Fifth edition (DSM-5), which was released in May of 2013, replacing the previous version, DSM-IV-TR10. This helps ensure that children are appropriately diagnosed and treated.
The tricky part about ADHD is that the symptoms are not very unique. On top of that, not every child displays the same symptoms or to the same degree. Many other problems, like anxiety, depression, and learning disabilities have similar symptoms11. Parents and teachers may not notice the fact that a child has ADHD because they associate their behavior as just being different and disregard the severity. One of the most common mistakes is that children with hyperactivity and impulsive symptoms are often thought to have disciplinary problems rather than ADHD.
After a person is diagnosed with ADHD, a doctor may prescribe medication or behavioral therapy. ADHD is commonly associated with depression, anxiety, poor self-esteem, relationship difficulties, and learning problems. A population study in Sweden found patients with ADHD have increased risks of attempted and completed suicide, after adjusting for other psychiatric disorders.9 They also found immediate relatives are at a higher risk, which supports the hypothesis that ADHD is genetic.
Stimulants are most commonly prescribed as they increase the neurotransmitter dopamine in the prefrontal cortex (which is the part of brain associated with attention). Ritalin, Concerta, and Adderall are some of the most popular stimulants. They help manage the primary symptoms of ADHD which include impulsivity, hyperactivity, and inattention. Antidepressants can also be prescribed. While these drugs have proven effective, medications are only a short term fix and their longevity is questioned. Not all children have the same responses to medication, and medications come with side effects. Some studies suggest that Ritalin causes the brain to develop abnormally in children. In addition, all stimulants have a risk of abuse and dependence.
There are three therapies used to help combat ADHD, which include cognitive behavioral therapy, social skills training, and family therapy. These techniques reward children for motor, impulse, and attentional control and give negative consequences for disruptive behavior. They can also participate in a program to improve the parent-child relationship and social skills. Therapy can be very useful because it helps the child think reflectively before reacting, but the right therapy might not be available to the child based on location, pricing, and hours11. Many schools have very limited resources and rarely have programs specifically for students with ADHD. The word therapy unfortunately also carries a negative connotation, which can deter parents from seeking this form of treatment.
A group of scientists used studies over a course of ten years to understand how stimulant drugs affect individuals with ADHD. They state that diagnosis of ADHD is difficult because of the symptoms being grouped, ungrouped, and re-grouped in the DSM. One particular study was a prospective observational study where participants were assigned into groups with medication, therapy, or a combination treatment. Stimulant medication was found to decrease severity of symptoms and increase achievement on reading and math tests. After 2-3 years of follow-up though, improvement was found to dissipate. Multiple studies have found that brain deficits in people with ADHD are non-progressive and associated with the disorder, not caused by the treatment of stimulants. Another controversy presented is whether dopamine activity is enhanced or depressed in people with ADHD. In 1999, a PET study confirmed that a stimulant medication causes an increase in synaptic dopamine. Other studies found high levels of dopamine transporter in individuals with ADHD, which accelerates the reuptake of synaptic dopamine and creates a dopamine deficit.12
Many studies on ADHD tend to find inconsistent results. Prevalence of this disorder can range from 0.5% to 26%. Association and cause are not clearly defined yet. In a debate, Dr. Sami Timimi points out that pharmaceutical companies are making huge profits off of stimulant drugs. Children are most likely to be diagnosed by age 7. This means our 2nd grade and younger students are on stimulants. That is an ethical question in itself. He states stimulants can have an effect on brain development. If this is true, the brain isn’t even fully developed until age 25 and could be really damaging to our children. The symptoms of ADHD could also describe your average child. Could this behavior point to bad parenting? Dr. Timimi blames parents, teachers and doctors for the increase in this disorder. Regarding doctors, he suggests, “ADHD is de-skilling for us as a profession as there is minimal skill involved in ticking off a checklist of symptoms and reaching for the prescription pad”13.
Professor Eric Taylor combats by pointing out that the prevalence of ADHD has not changed in the United Kingdom in over two decades. Mr. Taylor states that prevalence could change due to families, schools, and cultures varying in their measures of hyperactivity. For example, when using the same measures, Hong Kong had a higher rate of hyperactivity compared to London. When more objective measures were used, Hong Kong had a lower rate. Hyperactive behavior could have a bigger impact in Hong Kong because of the importance of academic success there.13
As stated previously, stimulant drugs have risk of abuse and dependence. A study suggests that 54% of students that have been prescribed stimulants for ADHD symptoms have been approached to sell their medication. In a nationally representative sample of US colleges, prevalence rates of nonmedical use of prescription stimulants ranged from 0% to 25%. This range is large because not many studies have focused on individuals that misuse non-prescribed ADHD medication. Individuals that are prescribed and misuse their medication are more likely to smoke cigarettes, binge drink, and use cocaine.14 Another study surveying young adults suggests that they have other purposes for this medication. It was found that 58% of college students misused these stimulants to concentrate, 43% for alertness, 43% to “get high,” and 14% for other motivation. The misuse of ADHD medication is a very controversial topic and is hotly debated in the scientific world today.14
Health problems that affect primarily children are always a reason for attention. ADHD has been studied vigorously, and still the majority of the findings surrounding it have been inconclusive. Studies have been done from different angles, from age, sex, and race to a variety of different potential risk factors. Each study has produced controversy because none of them have yet determined causes or associations that are strong enough. Even more debates arise when dealing with medications and treatment for ADHD, especially with their abuse by those without a prescription. With the prevalence of ADHD still rising, hopefully by raising awareness and continuing with further research, we can find out what causes this disorder and develop a cure and save our future generations.
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