Disorders usually first diagnosed in
infancy, childhood, or adolescence.
Attention-Deficit/Hyperactivity Disorder--

Attention-Deficit/Hyperactivity Disorder (ADHD)
previously known as Attention Deficit Disorder (ADD), is
generally considered to be a developmental disorder, largely neurological in nature, affecting about 5% of the
world's population.[1][2][3][4] The disorder typically presents itself during childhood, and is characterized by a
persistent pattern of inattention and/or hyperactivity, as well as forgetfulness, poor impulse control or impulsivity,
and distractibility.[5][6]ADHD is currently considered to be a persistent and chronic condition for which no medical
cure is available. ADHD is most commonly diagnosed in children and, over the past decade, has been increasingly
diagnosed in adults. About 60% of children diagnosed with ADHD retain the disorder as adults.[7] Studies show that
there is a familial transmission of the disorder which does not occur through adoptive relationships.[8] Twin studies
indicate that the disorder is highly heritable and that genetics contribute about three quarters of the total ADHD

While the majority of ADHD is believed to be genetic in nature,[8] roughly about 1/5 of all ADHD cases are thought
to be acquired after conception due to brain injury caused by either toxins or physical trauma prenatally or
postnatally.[8] According to a majority of medical research in the United States, as well as other countries, ADHD is
today generally regarded as a chronic disorder for which there are some effective treatments. Over 200 controlled
studies have shown that stimulant medication is an effective way to treat the symptoms of ADHD.[8][9] Methods of
treatment usually involve some combination of medication, behaviour modification, life style changes, and
counseling. Certain social critics are highly skeptical that the diagnosis denotes a genuine impairment and question
virtually all that is known about ADHD. The symptoms of ADHD are not as profoundly different from normal behavior
as are those of other chronic mental disorders. Still, ADHD has been shown to often impair functioning, and many
adverse life outcomes are associated with ADHD.


ADHD is a developmental disorder that is often said to be neurological in nature. The term "developmental" means
that certain traits such as impulse control significantly lag in development when compared to the general population.
This developmental lag has been estimated to range between 30-40 percent in ADHD sufferers in comparison to
their peers; consequently these delayed attributes are considered an impairment.

ADHD has also been classified as a behavior disorder and a neurological disorder or combinations of these
classifications such as neurobehavioural or neurodevelopmental disorders. These compounded terms are now more
frequently used in the field to describe the disorder.[citation needed] The behavioral classification for ADHD is not
completely accurate in that those with Predominately Inattentive ADHD often display few or no overt behaviors.


Based on DSM-IV criteria, three types of ADHD are identified:

* 1. ADHD, Combined Type: if both criteria 1A and 1B are met for the past 6 months
* 2. ADHD Predominantly Inattentive Type: if criterion 1A is met but criterion 1B is not met for the past six months
* 3. ADHD, Predominantly Hyperactive-Impulsive Type: if Criterion 1B is met but Criterion 1A is not met for the past
six months.


In the tenth edition of the International Statistical Classification of Diseases and Related Health Problems (ICD-10)
the symptoms of ADHD are given the name "Hyperkinetic disorders". When a conduct disorder (as defined by ICD-
10,[10]) is present, the condition is referred to as "Hyperkinetic conduct disorder". Otherwise the disorder is
classified as "Disturbance of Activity and Attention", "Other Hyperkinetic Disorders" or "Hyperkinetic Disorders,
Unspecified". The latter is sometimes referred to as, "Hyperkinetic Syndrome".[10]

The American Academy of Pediatrics Clinical Practice Guideline for children with ADHD emphasizes that a reliable
diagnosis is dependent upon the fulfillment of three criteria:[11]

* The use of explicit criteria for the diagnosis using the DSM-IV-TR.
* The importance of obtaining information about the child’s symptoms in more than one setting.
* The search for coexisting conditions that may make the diagnosis more difficult or complicate treatment planning.

The first criteria can be satisfied by using an ADHD-specific instrument such as the Conners' Rating Scale.[12] The
second criteria is best fulfilled by examining the individual's history. This history can be obtained from parents and
teachers, or a patient's memory.[13] The requirement that symptoms be present in more than one setting is very
important because the problem may not be with the child, but instead with teachers or parents who are too
demanding. The use of intelligence testing, psychological testing, and neuropsychological testing (to satisfy the third
criteria) is essential in order to find or rule out other factors that might be causing or complicating the problems
experienced by the patient.[14]

The Centers for Disease Control and Prevention (CDC) state that a diagnosis of ADHD 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 hyperthyroidism. 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.[15] 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.[16]

Common comorbid conditions are Oppositional Defiance Disorder (ODD). About 20% to 25% of children with ADHD
meet criteria for a learning disorder.[17] Learning disorders are more common when there are inattention symptoms.


PET scans of glucose metabolism in the brains of a normal adult (left) compared to an adult diagnosed with ADHD

PET scans of glucose metabolism in the brains of a normal adult (left) compared to an adult diagnosed with ADHD

The exact cause of ADHD remains unknown and in all probability ADHD is a heterogeneous disorder, meaning that
several causes could create very similar symptomology. Still, there is a wide body of evidence which indicates that
the overriding cause of ADHD is genetics. Research suggests that a large majority of ADHD arises from a
combination of various genes, many of which affect dopamine transporters.[20]

Suspect genes include the 10-repeat allele of the DAT1 gene,[21] the 7-repeat allele of the DRD4 gene,[21] and the
dopamine beta hydroxylase gene (DBH TaqI).[22]

Additionally, SPECT scans found people with ADHD to have reduced blood circulation,[23] and a significantly higher
concentration of dopamine transporters in the striatum which is in charge of planning ahead.[24][25]

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.[citation needed] 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.[26]

An early PET scan study found that global cerebral glucose metabolism was 8.1% lower in medication naive adults
who had been diagnosed as ADHD while children. The image on the right 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; these are
not pictures of individual brains, which would contain substantial overlap, these are images constructed to illustrate
group level differences. Additionally, the regions with the greatest deficit of activity in the ADHD patients (relative to
the controls) included the premotor cortex and the superior prefrontal cortex.[19]

A second study in adolescents failed to find statistically significant differences in global glucose metabolism between
ADHD patients and controls, but did find statistically significant deficits in 6 specific regions of the brains of the
ADHD patients (relative to the controls). Most notably, lower metabolic activity in one specific region of the left
anterior frontal lobe was significantly inversely correlated with symptom severity.[27] These findings strongly imply
that lowered activity in specific regions of the brain, rather than a broad global deficit, is involved in ADHD
symptoms. However, these readings are of subjects doing an assigned task. They could be found in ADHD
diagnosed patients because they simply were not attending to the task. Hence the parts of the brain used by others
doing the task would not show equal activity in the ADHD patients.

The estimated contribution of non genetic factors to the contribution of all cases of ADHD is 20 percent.[28] The
environmental factors implicated are common exposures and include alcohol, in utero tobacco smoke and lead
exposure. Lead concentration below the Center for Disease Control's action level account for slightly more cases of
ADHD than tobacco smoke (290 000 versus 270 000, in the USA, ages 4 to 15).[29] Complications during
pregnancy and birth (including premature birth) might also play a role. It has been observed that women who smoke
while pregnant are more likely to have children with ADHD.[30] This could be related to the fact than nicotine is
known to cause hypoxia (lack of oxygen) in utero, but it could also be that ADHD women have more probabilities to
smoke both in general and during pregnancy, being more likely to have children with ADHD due to genetic factors.

Head injuries can cause a person to present ADHD-like symptoms,[31] possibly because of damage done to the
patient's frontal lobes. Because these types of symptoms can be attributable to brain damage, the earliest
designation for ADHD was "Minimal Brain Damage".[32]

There is no compelling evidence that social factors alone can create ADHD. Many researchers believe that
attachments and relationships with caregivers and other features of a child's environment have profound effects on
attentional and self-regulatory capacities. It is noteworthy that a study of foster children found that an inordinate
number of them had symptoms closely resembling ADHD.[33] An editorial in a special edition of Clinical Psychology
in 2004 stated that "our impression from spending time with young people, their families and indeed colleagues from
other disciplines is that a medical diagnosis and medication is not enough. In our clinical experience, without
exception, we are finding that the same conduct typically labelled ADHD is shown by children in the context of
violence and abuse, impaired parental attachments and other experiences of emotional trauma."[34] Furthermore,
Complex Post Traumatic Stress Disorder can result in attention problems that can look like ADHD, as can Sensory
Integration Disorders.

Despite the lack of evidence that nutrition causes ADHD, studies have found that malnutrition is correlated with
attention deficits.[35]


There are several clinically proven effective options available to treat people diagnosed with ADHD. ADHD is treated
most effectively, and cost efficiently, with medication.[36] Psychotherapy is another option, with or without medication
[37] Omega-3 fatty acids, zinc, and magnesium may have benefits with regards to ADHD symptoms.[38][39]

Comorbid disorders or substance abuse can make finding the proper diagnosis and the right overall treatment more
costly and time-consuming.[40]


ADHD is a developmental disorder meaning that certain traits will be delayed in the ADHD individual. These traits will
develop but just at a much slower rate than the average person. With ADHD it has been estimated that this lag could
be as high as thirty to forty percent in the development of impulse control. Symptoms of ADHD are often seen by the
time a child enters preschool. Those with ADHD typically have a greater degree of parent-child conflict and
emotional reactivity. The incident of speech problems, central auditory processing difficulties, and coordination
problems are all higher than that of the general population. A marked decrease in academic skills such as reading,
spelling, or math is common with children who have ADHD.

During the elementary years an ADHD student will have more difficulties with work completion, productivity, planning,
remembering things needed for school, and meeting deadlines. Oppositional and socially aggressive behaviour is
seen in 40-70 percent of children at this age. Even ADHD kids with average to above average intelligence show
"chronic and severe underachievement". Fully 46% of those with ADHD have been suspended and 11% expelled.
[citation needed] Thirty seven percent of those with ADHD do not get a high school diploma even though many of
them will receive special education services.[8] The combined outcomes of the expulsion and dropout rates indicate
that almost half of all ADHD students never finish highschool.[41] Only five percent of those with ADHD will get a
college degree compared to twenty seven percent of the general population. (US Census, 2003)

Social impairment for those with ADHD are seen at both school and work. They often have more troubled
relationships with peers or family members. At the workplace they change jobs more often and are more likely to get
fired. Their income level does not rise as quickly as their peers even when education level, IQ, and their
neighborhood is accounted for. Thirty five percent of all ADHDers will be self employed in their mid-thirties. Those
with ADHD are at greater risk of: injury, abnormal risk taking, smoking, having learning disabilities, other mental
disorders, teen pregnancy, substance abuse, involvement with the criminal justice system, and having a poorer
driving record.[42]


There is no known way to prevent ADHD. Some studies indicate an association between mothers who smoke during
pregancy and a higher rate of ADHD in their children. Avoiding smoking, alcohol, and drugs during pregancy may
help prevent a higher risk of developing ADHD or similar behaviour in offspring.


ADHD's prevalence worldwide is estimated to be a bit over 5%, with most of the reported variability being due to
methodological characterstics of studies.[4] 10% of males, and (only) 4% of females have been diagnosed in the
U.S.[43] This apparent sex difference may reflect either a difference in susceptibility or that females with ADHD are
less likely to be diagnosed than males.[44][45]

ADHD predominantly inattentive (ADHD-I or ADHD-PI) is one of the four subtypes of Attention-Deficit Hyperactivity
Disorder (ADHD). While ADHD-PI is commonly referred to as Attention Deficit Disorder (ADD) due to a lack of
hyperactivity, but the terms "ADD" and "attention-deficit disorder" are no longer recognized in the Diagnostic and
Statistical Manual of Mental Disorders, fourth edition (DSM-IV).

Differences from traditional ADHD

ADHD-I is different from the other subtypes of ADHD in that it is characterized by inattention, daydreaming and
lethargy, but with little to none of the hyperactivity, impulsiveness or conduct disorders typical of the other three
ADHD subtypes ("ADHD predominantly hyperactive/impulsive", "ADHD combined", and "ADHD not otherwise
specified."). It is less studied and less understood than ADHD with hyperactivity because those with ADHD-I are not
as disruptive or active as those with "standard" ADHD and are less likely to be diagnosed.

There has been some debate[citation needed] as to whether all adults who meet the ADHD-I criteria should in fact
receive that diagnosis. It has been noted frequently[citation needed] that hyperactive children will lose some or all of
their hyperactive symptoms as they get older while retaining inattentive and impulsive symptoms. Some researchers
have suggested that these former hyperactive children should receive the ADHD-combined diagnosis. Hallowell and
Ratey (2005) suggest[1] that the manifestation of hyperactvity simply changes with adolescence and adulthood,
becoming a more generalized restlessness or tendency to fidget.

In the DSM-III, sluggishness, drowsiness, and daydreaming were listed as characteristics of ADHD. The symptoms
were removed from the ADHD criteria in DSM-IV because, although those with ADHD-I were found to have these
symptoms, this only occurred with the absence of hyperactive symptoms. These distinct symptoms were described
as sluggish cognitive tempo (SCT). There is some debate[citation needed] if those with SCT symptoms may be a
homogeneous grouping. It has been estimated that approximately half of those with ADHD-I can be better described
as having SCT symptoms.

Some experts, such as Dr. Russell Barkley,[2] argue that ADHD-I is so different from "traditional" ADHD that it should
be regarded as a distinct disorder. Barkley cites different symptoms among those with ADHD-I -- particularly the
almost complete lack of conduct disorders and high-risk, thrill-seeking behavior -- and markedly different responses
to stimulant medication.

DSM-IV Criteria

The DSM-IV allows for diagnosis of the predominantly inattentive subtype of ADHD if the individual presents six or
more of the following symptoms of inattention for at least six months to a point that is disruptive and inappropriate for
developmental level:

1. Often does not give close attention to details or makes careless mistakes in schoolwork, work, or other activities.
2. Often has trouble keeping attention on tasks or play activities.
3. Often does not seem to listen when spoken to directly.
4. Often does not follow instructions and fails to finish schoolwork, chores, or duties in the workplace (not due to
oppositional behavior or failure to understand instructions).
5. Often has trouble organizing activities.
6. Often avoids, dislikes, or doesn't want to do things that take a lot of mental effort for a long period of time (such
as schoolwork or homework).
7. Often loses things needed for tasks and activities (e.g. toys, school assignments, pencils, books, or tools).
8. Is often easily distracted.
9. Is often forgetful in daily activities.

Importantly for an ADHD-I diagnosis, some of the symptoms that cause impairment must have been present before
seven years of age, and must be present in two or more settings (e.g., at school or work and at home). There must
also be clear evidence of clinically significant impairment in social, academic, or occupational functioning. Lastly, the
symptoms must not occur exclusively during the course of a pervasive developmental disorder, schizophrenia, or
other psychotic disorder, and are not better accounted for by another mental disorder (e.g., mood disorder, anxiety
disorder, dissociative disorder, personality disorder.)

Examples of observed symptoms

* Failing to pay close attention to details or making careless mistakes when doing schoolwork or other activities
* Trouble keeping attention focused during play or tasks
* Appearing not to listen when spoken to
* Failing to follow instructions or finish tasks
* Avoiding tasks that require a high amount of mental effort and organization, such as school projects
* Frequently losing items required to facilitate tasks or activities, such as school supplies
* Excessive distractibility
* Forgetfulness
* Procrastination, inability to begin an activity
* Difficulties completing household chores

* References provided upon request.