Attention-Deficit Hyperactivity Disorder (ADHD) is a neurobehavioral developmental disorderaffecting about 3-5% of the world's population. It typically presents during childhood, and is characterized by a persistent pattern of impulsiveness and inattention, with or without a component of hyperactivity. ADHD occurs twice as commonly in boys as in girls. ADHD is generally a chronic disorder with 10 to 60% of individuals diagnosed in childhood continuing to meet diagnostic criteria in adulthood. As they mature, adolescents and adults with ADHD are likely to develop coping mechanisms to compensate for their impairment.
Though previously regarded as a childhood diagnosis, studies completed during the last few decades have shown that ADHD often continues throughout adulthood - though generally with a reduction in hyperactivity. ADHD has a strong genetic component. Methods of treatment usually involve some combination of medications, behavior modifications, life style changes, and counseling. The American Academy of Pediatrics states that stimulant medications and/or behavior therapy are appropriate and generally safe treatments for ADHD. Long term safety of stimulants however has not been determined and drug treatment of pre-school children is not recommended.
ADHD is one of the most controversial psychiatric disorders. The controversy involving clinicians, teachers, policymakers, parents, and the media with opinions regarding ADHD ranging from those who do not believe it exists to those who believe that there is genetic and physiological basis for the condition.
ADHD is best seen as the extreme of a continuous trait that is found throughout the population. It has been classified as a developmental disorder, a behavior disorder and a neurological disorder. ADHD is a developmental disorder where certain traits such as impulse control lag in development when compared to the general population. Using magnetic resonance imaging, this developmental lag has been estimated to range from 3 to 5 years in the prefrontal cortex.. These delays are considered to cause impairment. ADHD has also been classified as a behavior disorder and a neurological disorder.
The DSM IV categorises the symptoms of ADHD into two clusters: inattention symptoms and hyperactivity/impulsivity symptoms. Most ordinary people exhibit some of these behaviors but not to the point where they significantly interfere with the person's work, relationships, or studies or cause anxiety or depression.
Hyperactivity is common among children with ADHD but tends to disappear during adulthood. However, over half of children with ADHD continue to have some symptoms of inattention throughout their lives.
Inattention and "hyperactive" behavior are not the only problems with children with ADHD. ADHD exists alone in only about 1/3 of the children diagnosed with it. Many of these co-existing conditions require other courses of treatment and should be diagnosed separately instead of being grouped in the ADHD diagnosis. Some of the associated conditions are:
Although the reasons are not clear, it has long been observed (and is not controversial) that many children seem to "outgrow" ADHD. These individuals include those with and without various combinations of medication and/or therapy, although both have proven generally effective and safe in easing symptoms and reducing impairment. It is also known that many adolescents and adults develop coping skills as they mature to offset impairments. An individual's development of helpful coping skills may be enhanced by therapy, but also may result with or without conscious effort of the individual.
Researchers believe that a large majority of ADHD arises from a combination of various genes, many of which affect dopamine transporters. Candidate genes include dopamine transporter, dopamine receptor D4, dopamine beta-hydroxylase, monoamine oxidase A, catecholamine-methyl transferase, serotonin transporter promoter (SLC6A4), 5-hydroxytryptamine 2A receptor (5-HT2A), 5-hydroxytryptamine 1B receptor (5-HT1B), the 10-repeat allele of the DAT1 gene, the 7-repeat allele of the DRD4 gene, and the dopamine beta hydroxylase gene (DBH TaqI).
The broad selection of targets indicates that ADHD does not follow the traditional model of a "genetic disease" and should be viewed as a complex interaction among genetic and environmental factors. Even though all these genes might play a role to date no single gene has been shown to make a major contribution to ADHD.
Environmental factors implicated include alcohol and tobacco smoke exposure during pregnancy and lead exposure after birth. Smoking relation to ADHD could be due nicotine causing hypoxia (lack of oxygen) in utero, however it could also be that women with ADHD are more likely to smoke and therefore due to the strong genetic component of ADHD more likely to have children with ADHD. Complications during pregnancy and birth—including premature birth—might also play a role.
Current evidence does not support an association between head injuries and ADHD.
Preliminary evidence suggests that Omega-3/Omega-6 supplementation reduces ADHD symptoms.
The hunter vs. farmer theory is a hypothesis proposed by Thom Hartmann, a radio host, about the origins of attention-deficit hyperactivity disorder (ADHD). He believes that these conditions may be a result of adaptive behavior of the species. His theory believes that those with ADHD retained some of the older hunter characteristics.
Proponents of this theory assert that atypical (neurodivergent) neurological development is a normal human difference that is to be tolerated and respected as any other human difference. Social critics argue that while biological factors may obviously play a large role in difficulties sitting still and/or concentrating on schoolwork in some children, for a variety of reasons they have failed to integrate into the social expectations that others have of them.
Social critics question whether ADHD is wholly or even predominantly a biological illness. A minority of these critics maintain that ADHD was, "invented and not discovered". They believe that no disorder exists and that the behaviour observed is not abnormal and can be better explained by environmental causes or just the personality of the "patient."
The pathophysiology of ADHD is unclear and there are a number of competing theories.
In one study a delay in development of certain brain structures by an average of three years occurred in ADHD elementary school aged patients. The delay was most prominent in the frontal cortex and temporal lobe, which are believed to be responsible for the ability to control and focus thinking. In contrast, the motor cortex in the ADHD patients was seen to mature faster than normal, suggesting that both slower development of behavioral control and advanced motor development might be required for the fidgetiness that characterize an ADHD diagnosis.
The same laboratory had previously found involvement of the "7-repeat" variant of the dopamine D4 receptor gene, which accounts for about 30 percent of the genetic risk for ADHD, in unusual thinness of the cortex of the right side of the brain; however, in contrast to other variants of the gene found in ADHD patients, the region normalized in thickness during the teen years in these children, coinciding with clinical improvement.
Additionally, SPECT scans found people with ADHD to have reduced blood circulation (indicating low neural activity), and a significantly higher concentration of dopamine transporters in the striatum which is in charge of planning ahead. Medications focused on treating ADHD (such as methylphenidate) work by reducing dopamine reuptake in certain areas of the brain, such as those that control and regulate concentration. As dopamine is a stimulant, this increases neural activity and thus blood flow in these areas (blood flow is a marker for neural activity). A study by the U.S. Department of Energy’s Brookhaven National Laboratory in collaboration with Mount Sinai School of Medicine in New York suggest that it is not the dopamine transporter levels that indicate ADHD, but the brain's ability to produce dopamine itself. The study was done by injecting 20 ADHD subjects and 25 control subjects with a radiotracer that attaches itself to dopamine transporters. The study found that it was not the transporter levels that indicated ADHD, but the dopamine itself. ADHD subjects showed lower levels of dopamine across the board. They speculated that since ADHD subjects had lower levels of dopamine to begin with, the number of transporters in the brain was not the telling factor. In support of this notion, plasma homovanillic acid, an index of dopamine levels, was found to be inversely related not only to childhood ADHD symptoms in adult psychiatric patients, but to "childhood learning problems" in healthy subjects as well.
Although there is evidence for dopamine abnormalities in ADHD, it is not clear whether abnormalities of the dopamine system are the molecular abnormality of ADHD or a secondary consequence of a problem elsewhere. Researchers have described a form of ADHD in which the abnormality appears to be sensory overstimulation resulting from a disorder of ion channels in the peripheral nervous system.
An early PET scan study found that global cerebral glucose metabolism was 8% lower in medication-naive adults who had been diagnosed as ADHD while children. The image on the left illustrates glucose metabolism in the brain of a 'normal' adult while doing an assigned auditory attention task; the image on the right illustrates the areas of activity in the brain of an adult who had been diagnosed with ADHD as a child when given that same task. The regions with the greatest deficit of activity included the premotor cortex and the superior prefrontal cortex. The significance of the research by Dr. Alan Zametkin that produced these images is still not definative.
No objective test exists to make a diagnosis of ADHD. It thus remains a clinical diagnosis.
Many of the symptoms of ADHD occur from time to time in everyone; in patients with ADHD, the frequency of these symptoms is greater and significantly impairs their life. This impairment must occur in multiple settings to be classified as ADHD. As with many other psychiatric and medical disorders, the formal diagnosis is made by a qualified professional in the field based on a set number of criteria. In the USA these criteria are laid down by the American Psychiatric Association in their Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), 4th edition. Based on the DSM-IV criteria listed below, three types of ADHD are classified:
The terminology of ADD expired with the revision of the most current version of the DSM. Consequently, ADHD is the current nomenclature used to describe the disorder as one distinct disorder which can manifest itself as being a primary deficit resulting in hyperactivity/impulsivity (ADHD, predominately hyperactive-impulsive type) or inattention (ADHD predominately inattentive type) or both (ADHD combined type).
II. Some symptoms that cause impairment were present before age 7 years.
III. Some impairment from the symptoms is present in two or more settings (e.g. at school/work and at home).
IV. There must be clear evidence of significant impairment in social, school, or work functioning.
V. The symptoms do not happen only during the course of a Pervasive Developmental Disorder, Schizophrenia, or other Psychotic Disorder. The symptoms are not better accounted for by another mental disorder (e.g. Mood Disorder, Anxiety Disorder, Dissociative Disorder, or a Personality Disorder).
All three criteria are determined using the patients history given by the parents, teachers and/or the patient.
The Centers for Disease Control and Prevention (CDC) state that a diagnosis of ADD should only be made by trained health care providers, as many of the symptoms may also be part of other conditions, such as bodily illness or other physiological disorders, such as hypothyroidism. It is not uncommon that physically and mentally nonpathological individuals exhibit at least some of the symptoms from time to time. Severity and pervasiveness of the symptoms leading to prominent functional impairment across different settings (school, work, social relationships) are major factors in a positive diagnosis.
Adults often continue to be impaired by ADHD. Adults with ADHD are diagnosed under the same criteria, including the stipulation that their symptoms must have been present prior to the age of seven. Adults face some of their greatest challenges in the areas of self-control and self-motivation, as well as executive functioning, usually having more symptoms of inattention and fewer of hyperactivity or impulsiveness than children do.
Common comorbid conditions are Oppositional Defiance Disorder (ODD). About 20% to 25% of children with ADD meet criteria for a learning disorder. Learning disorders are more common when there are inattention symptoms.
Methods of treatment often involve some combination of medications, behavior modifications, life style changes, and counseling.
Long term safety, however, has not been determined. There are no randomized controlled trials assessing the harms or benefits of treatment beyond two years. The American Heart Association and the American Academy of Pediatrics feels that it is prudent to carefully assess children for heart conditions before treating them with stimulant medications. The FDA has added black box warning to some ADHD medications. Amphetamines (Adderall ) has warnings about potential for abuse, drug dependence, and sudden death.
Comorbid disorders or substance abuse can make the diagnosis and the treatment of ADHD more difficult. Psychosocial therapy is useful in treating some comorbid conditions.
37% of those with ADHD do not get a high school diploma even though many of them will receive special education services. The combined outcomes of the expulsion and dropout rates indicate that almost half of all ADHD students never finish high school. In the United States, less than 5% of individuals with ADHD get a college degree compared to 28% of the general population.
The DSM-II in 1968 began to call it "Hyperkinetic Reaction of Childhood" even though the professionals were aware that many of the children so diagnosed exhibited attention deficits without any signs of hyperactivity. In 1980, the DSM-III introduced "ADD (Attention-Deficit Disorder) with or without hyperactivity." That terminology (ADD) technically expired with the revision in 1987 to ADHD in the DSM-III-R. In the DSM-IV, published in 1994, ADHD with sub-types was presented. The current version (as of 2008), the DSM-IV-TR was released in 2000, primarily to correct factual errors and make changes to reflect recent research. (ADHD was basically unchanged).
Under the DSM-IV, within the ADHD syndrome, there are three sub-types, including one which lacks the hyperactivity component. Approximately one-third of people with ADHD have the predominantly inattentive type (ADHD-I), meaning that they do not have the hyperactive or overactive behavior components of the other ADHD subtypes.
Even today, the ADHD terminology is objectionable to many. There is some preference for using the ADHD-I, ADD, and AADD terminology when describing individuals lacking the hyperactivity component, especially among older adolescents and adults who find the term "hyperactive" inaccurate, inappropriate and even derogatory.
In 493 BCE, physician-scientist Hippocrates described a condition that seems to be compatible with what we now know as ADHD. He described patients who had "quickened responses to sensory experience, but also less tenaciousness because the soul moves on quickly to the next impression". Hippocrates attributed this condition to an "overbalance of fire over water”. His remedy for this "overbalance" was "barley rather than wheat bread, fish rather than meat, water drinks, and many natural and diverse physical activities.
Russell Barkley has argued that Shakespeare made reference to a "malady of attention" in King Henry VII, although the actual quote appears to come from King Henry IV, part II.
In 1975, pemoline (Cylert) was approved by the FDA for use in the treatment of ADHD. While an effective agent for managing the symptoms, the development of liver failure in 14 cases over the next 27 years would result in the manufacturer withdrawing this medication from the market. New delivery systems for medications were invented in 1999 that eliminated the need for multiple doses across the day or taking medication at school. These new systems include pellets of medication coated with various time-release substances to permit medications to dissolve hourly across an 8–12 hour period (Metadate CD, Adderall XR, Focalin XR) and an osmotic pump that extrudes a liquid methylphenidate sludge across an 8–12 hour period after ingestion (Concerta).
In 2003, atomoxetine (Strattera) received the first FDA approval for a nonstimulant drug to be used specifically for ADHD. In 2007, lisdexamfetamine (Vyvanse) becomes the first prodrug to receive FDA approval for ADHD. The landmark study of 1999 – The largest study of treatment for ADHD in history – is published in the American Journal of Psychiatry. Known as the Multimodal Treatment Study of ADHD (MTA Study), it involved more than 570 children with ADHD at 6 sites in the United States and Canada randomly assigned to 4 treatment groups. Results generally showed that medication alone was more effective than psychosocial treatments alone, but that their combination was beneficial for some subsets of ADHD children beyond the improvement achieved only by medication. More than 40 studies have subsequently been published from this massive dataset.
It has been estimated that about eight million adults have ADHD in the United States. In 2004, noted researchers estimated the yearly income loss for adults with ADHD in the United States as $77 billion. This may be partially because it is also estimated that only 15% of adults in the U.S. with ADHD are aware that they have the disorder, although many adults struggle with it.
A diagnosis of ADHD may offer an adult insight into their behaviors and allow the patient to become more aware and seek help with coping and treatment strategies. Studies show that adult ADHD is treated successfully with a combination of medication and behavior therapy.
Many professionals have speculated that in the next DSM (tentatively DSM-V), ADHD in adults may be differentiated from the syndrome as it occurs in children. Only recognized as occurring in adults in 1978, it is currently not addressed separately. Obstacles that clinicians face when assessing adults who may have ADHD include developmentally inappropriate diagnostic criteria, age-related changes, comorbidities, and the possibility that high intelligence or situational factors can mask ADHD symptoms. For adults, most treatments with medication and therapy are basically similar; a mature patient may more able to provide feedback and help self-direct the process.
Another study looked at Colombian and Castillejos, Zambales schoolchildren to examine whether ADHD is merely a cultural phenomenon, or a cultural phenomenon with a biological basis. The authors conclude: “If ADHD were explicable as a culturally formulated psychiatric phenomenon, then it would be predicted that the same hyperactive and inattentive behaviors displayed in different cultural contexts would be associated with differing degrees of harmful dysfunction. In this study we found that children's hyperactive and inattentive behavior were similarly expressed in diverse populations and systematically related to children's social and academic wellbeing across those varied cultural contexts.” This study was later criticized for assuming a homogenous culture for the United States population, failing to mention the socioeconomic backgrounds of the populations, and using two study populations that share European cultural origins.
Attention-deficit hyperactivity disorder (ADHD) "is a highly controversial pediatric disorder despite being a well validated clinical diagnosis". The controversy involving clinicians, teachers, policymakers, parents, and the media with opinions regarding ADHD ranging from those who do not believe it exists to those who believe that there is genetic and physiological basis for the condition. The controversy is discussed in depth in the Sept. 2008 UK publication of the NICE guidelines on ADHD.
Researchers from McMaster identified six features of ADHD that contribute to its controversial nature: 1) it is a clinical diagnosis for which there are no laboratory or radiological confirmatory tests or specific physical features; 2) diagnostic criteria have changed frequently; 3) there is no curative treatment, so long-term therapies are required; 4) therapy often includes stimulant drugs that are thought to have abuse potential; and 5) the rates of diagnosis and of treatment substantially differ across countries.
The British Psychological Society states that: “The idea that children who don’t attend or who don’t sit still in school have a mental disorder is not entertained by most British clinicians.”
In the Harvard Review of Psychiatry, three authors from Departments of Political Science and Psychology at the University of California campuses in Richmond and Berkeley stated "ADHD is one of the most controversial psychiatric disorders, in part because it is also the most commonly diagnosed mental disorder among minors. There is concern about the effects of an ADHD diagnosis on the mental state and self-esteem of patients. There is disagreement over the cause of ADHD and there are questions about research methodologies , and skepticism toward its classification as a mental disorder. Social critics point to changing standards of diagnosis , such as the American Academy of Pediatrics (AAP) issuing a more careful set of standards in 2000 to aid clinicians than merely using DSM-IV.
Concern exists that "elevated but still developmentally normal levels of motor activity, impulsiveness, or inattention" traits of childhood could be inappropriately interpreted as ADHD. The National Institute of Mental Health states that, "stimulant drugs, when used with medical supervision, are usually considered quite safe. Some parents and professionals have raised questions about the side effects of drugs and their long term use. Calls for greater scrutiny are made by some news sources, social critics, religions, and medical professionals. Ethical and legal issues with regard to treatment have been key areas of concern for these critics. "Alternative theory" critics contend that the symptoms of ADHD can be better explained by the Hunter vs. farmer theory or Neurodiversity. Fringe critics question if ADHD exists at all as a disorder social construct theory of ADHD. Fringe critics question if ADHD exists at all as a disorder.