Attention deficit hyperactivity disorder

Attention deficit hyperactivity disorder
Children with ADHD find it more difficult to focus and to complete their schoolwork.

Attention deficit hyperactivity disorder (ADHD, similar to hyperkinetic disorder in the ICD-10) is a neurodevelopmental psychiatric disorder  in which there are significant problems with executive functions (e.g., attentional control and inhibitory control) that cause attention deficits, hyperactivity, or impulsiveness which is not appropriate for a person's age.  These symptoms must begin by age six to twelve and persist for more than six months for a diagnosis to be made.  In school-aged individuals inattention symptoms often result in poor school performance. Although it causes impairment, particularly in modern society, many children with ADHD have a good attention span for tasks they find interesting.

Despite being the most commonly studied and diagnosed psychiatric disorder in children and adolescents, the cause in the majority of cases is unknown. It affects about 6–7% of children when diagnosed via the DSM-IV criteria  and 1–2% when diagnosed via the ICD-10 criteria.  Rates are similar between countries and depend mostly on how it is diagnosed.  ADHD is diagnosed approximately three times more in boys than in girls.  About 30–50% of people diagnosed in childhood continue to have symptoms into adulthood and between 2–5% of adults have the condition.  The condition can be difficult to tell apart from other disorders as well as that of high normal activity.

ADHD management usually involves some combination of counseling, lifestyle changes, and medications. Medications are only recommended as a first-line treatment in children who have severe symptoms and may be considered for those with moderate symptoms who either refuse or fail to improve with counseling.  Stimulant therapy is not recommended in preschool-aged children.  Treatment with stimulants is effective for up to 14 months; however, its long term effectiveness is unclear.  Adolescents and adults tend to develop coping skills which make up for some or all of their impairments.

ADHD, its diagnosis, and its treatment have been considered controversial since the 1970s.  The controversies have involved clinicians, teachers, policymakers, parents, and the media. Topics include ADHD's causes and the use of stimulant medications in its treatment.  Most healthcare providers accept ADHD as a genuine disorder, and the debate in the scientific community mainly centers on how it is diagnosed and treated.

Signs and symptoms

Inattention, hyperactivity (restlessness in adults), disruptive behavior, and impulsivity are common in ADHD.  Academic difficulties are frequent as are problems with relationships.  The symptoms can be difficult to define as it is hard to draw a line at where normal levels of inattention, hyperactivity, and impulsivity end and significant levels requiring interventions begin.

To be diagnosed per DSM-5, symptoms must be observed in multiple settings for six months or more and to a degree that is much greater than others of the same age.  They must also cause problems in the person's social, academic, or work life.

Based on the presenting symptom ADHD can be divided into three subtypes: predominantly inattentive, predominantly hyperactive-impulsive, and combined type.

An individual with inattention may have some or all of the following symptoms:

• Be easily distracted, miss details, forget things, and frequently switch from one activity to another.
• Have difficulty maintaining focus on one task.
• Become bored with a task after only a few minutes, unless doing something enjoyable.
• Have difficulty focusing attention on organizing and completing a task or learning something new.
• Have trouble completing or turning in homework assignments often losing things (e.g. pencils,toys, assignments) needed to complete tasks or activities.
• Not seem to listen when spoken to.
• Daydream, become easily confused, and move slowly.
• Have difficulty processing information as quickly and accurately as others.
• Struggle to follow instructions.

An individual with hyperactivity may have some or all of the following symptoms:

• Fidget and squirm in their seats.
• Talk nonstop.
• Dash around touching or playing with anything and everything in sight.
• Have trouble sitting still during dinner, school, doing homework, and story time.
• Be constantly in motion.
• Have difficulty doing quiet tasks or activities.

These hyperactivity symptoms tend to go away with age and turning "inner restlessness" in teens and adults with ADHD.

An individual with impulsivity may have some or all of the following symptoms:

• Be very impatient
• Blurt out inappropriate comments, show their emotions with out restraint and act with out regard for consequences.
• Have difficulty waiting for things they want or waiting their turns in games.
• Often interrupt conversations or others activities.

People with ADHD more often have difficulties with social skills, such as social interaction and forming and maintaining friendships. This is true of all subtypes. About half of children and adolescents with ADHD experience social rejection by their peers compared to 10-15% of non-ADHD children and adolescents. People with ADHD have attention deficits which cause difficulty processing verbal and nonverbal language which can negatively affect social interaction. They also may drift off during conversations, and miss social cues.

Difficulties managing anger are more common in children with ADHD as are poor handwriting and delays in speech, language and motor development. Although it cause significant impairment, particularly in modern society many children with ADHD have a good attention span for tasks they find interesting.

Associated disorders

In children ADHD occurs with other disorders about 2/3 of the time. Some commonly associated conditions include:

•  Learning disabilities have been found to occur in about 20 - 30% of children with ADHD. Learning disabilities can include developmental speech and language disorders and the academic skills disorders. ADHD however is not considered a learning disability but it very frequently causes academic difficulties.
• Tourette syndrome has been found to occur more commonly in the ADHD population. 
• Oppositional defiant disorder (ODD) and conduct disorder (CD), which occur with ADHD in about 50% and 20% of cases respectively. They are characterized by antisocial behaviors such as stubbornness aggression, frequent temper tantrums, deceitfulness, lying, and stealing. About half of those with hyperactivity and ODD or CD develop antisocial personality disorder in adulthood. Brain imaging supports that conduct disorder and ADHD are separate conditions.
•   Primary disorder of vigilance, which is characterized by poor attention and concentration as well as difficulties staying awake. These children tend to fidget, yawn and stretch and appear to be hyperactive in order to remain alert and active.
• Hypokalemic sensory overstimulation is present in less than 50% of people with ADHD and may be the molecular mechanism for many people with ADHD.
• Mood disorders (especially bipolar disorder and major depressive disorder). Boys diagnosed with the combined ADHD subtype are more likely to have a mood disorder.  Adults with ADHD sometimes also have bipolar disorder, which requires careful assessment to accurately diagnose and treat both conditions
• Anxiety disorders have been found to occur more commonly in the ADHD population.
• Obsessive-compulsive disorder (OCD) can co-occur with ADHD and shares many of its characteristics.
• Substance use disorders. Adolescents and adults with ADHD are at increased risk of developing a substance use problem.  This is most commonly with alcohol or cannabis.  The reason for this may be an altered reward pathway in the brains of ADHD individuals.  This makes the evaluation and treatment of ADHD more difficult, with serious substance misuse problems usually treated first due to their greater risks.
• Restless legs syndrome has been found to be more common in those with ADHD and is often due to iron deficiency anaemia.  However, restless legs can simply be a part of ADHD and requires careful assessment to differentiate between the two disorders.
• Sleep disorders and ADHD commonly co-exist. They can also occur as a side effect of medications used to treat ADHD. In children with ADHD, insomnia is the most common sleep disorder with behavioral therapy the preferred treatment.  Problems with sleep initiation are common among individuals with ADHD but often they will be deep sleepers and have significant difficulty getting up in the morning.  Melatonin is sometimes used in children who have sleep onset insomnia.

There is an association with persistent bed wetting,  language delay, and developmental coordination disorder (DCD), with about half of people with DCD having ADHD. The language delay in people with ADHD can include problems with auditory processing disorders such as short-term auditory memory weakness, difficulty following instructions, slow speed of processing written and spoken language, difficulties listening in distracting environments e.g. the classroom, and weakness in reading comprehension.

Cause

The cause of most cases of ADHD is unknown; however, it is believed to involve interactions between genetic and environmental factors.n Certain cases are related to previous infection of or trauma to the brain.

Genetics

Twin studies indicate that the disorder is often inherited from one's parents with genetics determining about 75% of cases.  Siblings of children with ADHD are three to four times more likely to develop the disorder than siblings of children without the disorder.  Genetic factors are also believed to be involved in determining whether ADHD persists into adulthood.

Environment

Environmental factors are believed to play a lesser role. Alcohol intake during pregnancy can cause fetal alcohol spectrum disorder which can include symptoms similar to ADHD.  Exposure to tobacco smoke during pregnancy can cause problems with central nervous system development and can increase the risk of ADHD.  Many children exposed to tobacco do not develop ADHD or only have mild symptoms which do not reach the threshold for a diagnosis. A combination of a genetic predisposition with tobacco exposure may explain why some children exposed during pregnancy may develop ADHD and others do not.  Children exposed to lead, even low levels, or polychlorinated biphenyls may develop problems which resemble ADHD and fulfill the diagnosis.  Exposure to the organophosphate insecticides chlorpyrifos and dialkyl phosphate is associated with an increased risk; however, the evidence is not conclusive.

Society

The diagnosis of ADHD can represent family dysfunction or a poor educational system rather than an individual problem. Some cases may be explained by increasing academic expectations, with a diagnosis being a method for parents in some countries to get extra financial and educational support for their child. The youngest children in a class have been found to be more likely to be diagnosed as having ADHD possibly due to their being developmentally behind their older classmates. Behavior typical of ADHD occurs more commonly in children who have experienced violence and emotional abuse.

Pathophysiology

Current models of ADHD suggest that it is associated with functional impairments in some of the brain's neurotransmitter systems, particularly those involving dopamine and norepinephrine.  The dopamine and norepinephrine pathways that originate in the ventral tegmental area and locus coeruleus project to diverse regions of the brain and govern a variety of cognitive processes.  The dopamine pathways and norepinephrine pathways which project to the prefrontal cortex and striatum (particularly, the nucleus accumbens) are directly responsible for modulating executive function (cognitive control of behavior), motivation, and reward perception;  these pathways are known to play a central role in the pathophysiology of ADHD. Larger models of ADHD with additional pathways have been proposed.

Neurotransmitter pathways

Previously it was thought that the elevated number of dopamine transporters in people with ADHD was part of the pathophysiology but it appears that the elevated numbers are due to adaptation to exposure to stimulants.  Current models involve the mesocorticolimbic dopamine pathway and the locus coeruleus-noradrenergic system.  ADHD psychostimulants possess treatment efficacy because they increase neurotransmitter activity in these systems.  There may additionally be abnormalities in serotoninergic and cholinergic pathways.   Neurotransmission of glutamate, a cotransmitter with dopamine in the mesolimbic pathway,  seems to be also involved.

Executive function and motivation

ADHD symptoms involve a difficulty with executive functions.  Executive function refers to a number of mental processes that are required to regulate, control, and manage daily life tasks  Some of these impairments include problems with organization, time keeping, excessive procrastination, concentration, processing speed, regulating emotions, and utilizing working memory.  People usually have decent long-term memory.  The criteria for an executive function deficit are met in 30–50% of children and adolescents with ADHD.  One study found that 80% of individuals with ADHD were impaired in at least one executive function task, compared to 50% for individuals without ADHD.  Due to the rates of brain maturation and the increasing demands for executive control as a person gets older, ADHD impairments may not fully manifest themselves until adolescence or even early adulthood.

ADHD has also been associated with motivational deficits in children.  Children with ADHD find it difficult to focus on long-term over short-term rewards, and exhibit impulsive behavior for short-term rewards.  In these individuals, a large amount of positive reinforcement effectively improves task performance.  ADHD stimulants may improve persistence in ADHD children as well.

Diagnosis

ADHD is diagnosed by an assessment of a person's childhood behavioral and mental development, including ruling out the effects of drugs, medications and other medical or psychiatric problems as explanations for the symptoms.  It often takes into account feedback from parents and teachers  with most diagnoses begun after a teacher raises concerns.  It may be viewed as the extreme end of one or more continuous human traits found in all people.  Whether someone responds to medications does not confirm or rule out the diagnosis. As imaging studies of the brain do not give consistent results between individuals, they are only used for research purposes and not diagnosis. 

In North America, the DSM-IV or DSM-5 criteria are often used for diagnosis, while European countries usually use the ICD-10. With the DSM-IV criteria a diagnosis of ADHD is 3–4 times more likely than with the ICD-10 criteria.  It is classified as neurodevelopmental psychiatric disorder.  Additionally, it is classified as a disruptive behavior disorder along with oppositional defiant disorder, conduct disorder, and antisocial personality disorder.  A diagnosis does not imply a neurological disorder.

Associated conditions that should be screened for include anxiety, depression, oppositional defiant disorder, conduct disorder, and learning and language disorders. Other conditions that should be considered are other neurodevelopmental disorders, tics, and sleep apnea.

Diagnosis of ADHD using quantitative electroencephalography (QEEG) is an ongoing area of investigation, although the value of QEEG in ADHD is currently unclear.  In the United States, the Food and Drug Administration has approved the use of QEEG to evaluate the morbidity of ADHD.

Diagnostic and Statistical Manual

As with many other psychiatric disorders, formal diagnosis is made by a qualified professional based on a set number of criteria. In the United States, these criteria are defined by the American Psychiatric Association in the DSM. Based on the DSM criteria, there are three sub-types of ADHD:

1. ADHD predominantly inattentive type (ADHD-PI) presents with symptoms including being easily distracted, forgetful, daydreaming, disorganization, poor concentration, and difficulty completing tasks.  Often people refer to ADHD-PI as "attention deficit disorder" (ADD), however, the latter has not been officially accepted since the 1994 revision of the DSM.
2. ADHD, predominantly hyperactive-impulsive type presents with excessive fidgetiness and restlessness, hyperactivity, difficulty waiting and remaining seated, immature behavior; destructive behaviors may also be present.
3. ADHD, combined type is a combination of the first two subtypes.

This subdivision is based on presence of at least six out of nine long-term (lasting at least six months) symptoms of inattention, hyperactivity–impulsivity, or both. To be considered, the symptoms must have appeared by the age of six to twelve and occur in more than one environment (e.g. at home and at school or work). The symptoms must be not appropriate for a child of that age  and there must be evidence that it is causing social, school or work related problems.

Most children with ADHD have the combined type. Children with the inattention subtype are less likely to act out or have difficulties getting along with other children. They may sit quietly, but without paying attention resulting in the child difficulties being overlooked.

International Classification of Diseases

In the ICD-10, the symptoms of "hyperkinetic disorder" are analogous to ADHD in the DSM-5.  When a conduct disorder (as defined by ICD-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.

Adults

Adults with ADHD are diagnosed under the same criteria, including that their signs must have been present by the age of six to twelve. Questioning parents or guardians as to how the person behaved and developed as a child may form part of the assessment; a family history of ADHD also adds weight to a diagnosis. While the core symptoms of ADHD are similar in children and adults they often present differently in adults than in children, for example excessive physical activity seen in children may present as feelings of restlessness and constant mental activity in adults.

Differential diagnosis

• Depression
• Anxiety disorder
• Mania

Symptoms of ADHD such as low mood and poor self-image, mood swings, and irritability can be confused with dysthymia, cyclothymia or bipolar disorder as well as with borderline personality disorder.  Some symptoms that are due to anxiety disorders, antisocial personality disorder, developmental disabilities or mental retardation or the effects of substance abuse such as intoxication and withdrawal can overlap with some ADHD. These disorders can also sometimes occur along with ADHD. Medical conditions which can cause ADHD type symptoms include:hyperthyroidism, seizure disorder, lead toxicity, hearing deficits, hepatic disease, sleep apnea, drug interactions, and head injury.

Primary sleep disorders may affect attention and behavior and the symptoms of ADHD may affect sleep.  It is thus recommended that children with ADHD be regularly assessed for sleep problems.  Sleepiness in children may result in symptoms ranging from the classic ones of yawning and rubbing the eyes, to hyperactivity and inattentiveness.  Obstructive sleep apnea can also cause ADHD type symptoms. 

ADHD symptoms which may be related to other disorders
Feelings of guilt, hopelessness, low self-esteem, or unhappiness Loss of interest in hobbies, regular activities, sex, or work Fatigue Too little, poor, or excessive sleep Difficulty paying attention Changes in appetite Irritability Low tolerance for stress Thoughts of suicide Unexplained pain	Worry or a persistent feeling of anxiety Irritability Inability to relax Being hyperalert Tires easily Low tolerance for stress Difficulty paying attention	Excessive happiness Hyperactivity Racing thoughts Aggression Excessive talking Grandiose delusions Decreased need for sleep Inappropriate social behavior Difficulty paying attention

Management

The management of ADHD typically involves counseling or medications either alone or in combination. While treatment may improve long-term outcomes, it does not get rid of negative outcomes entirely.

Behavioral therapies

There is good evidence for the use of behavioral therapies in ADHD  and they are the recommended first line treatment in those who have mild symptoms or are preschool-aged.  Psychological therapies used include: psychoeducational input, behavior therapy, cognitive behavioral therapy (CBT), interpersonal psychotherapy, family therapy, school-based interventions, social skills training, parent management training,  and neurofeedback.   Parent training and education have been found to have short-term benefits. There is little high quality research on the effectiveness of family therapy for ADHD, but the evidence that exists shows that it is similar to community care and better than a placebo. Several ADHD specific support groups exist as informational sources and may help families cope with ADHD.

Medication

Stimulant medications are the pharmaceutical treatment of choice.  They have at least some effect in the short term in about 80% of people.  There are a number of non-stimulant medications, such as atomoxetine, bupropion, guanfacine, and clonidine that may be used as alternatives. There are no good studies comparing the various medications; however, they appear more or less equal with respect to side effects.  Stimulants appear to improve academic performance while atomoxetine does    There are a number of non-stimulant medications, such as atomoxetine, bupropion, guanfacine, and clonidine that may be used as alternatives.  There are no good studies comparing the various medications; however, they appear more or less equal with respect to side effects.  Stimulants appear to improve academic performance while atomoxetine does not.  There is little evidence on their effects on social behaviors.  Medications are not recommended for preschool children, as the long-term effects in this age group are not known.  The long-term effects of stimulants generally are unclear with one study finding benefit, another finding no benefit and a third finding evidence of harm.  Magnetic resonance imaging studies suggest that long-term treatment with amphetamine or methylphenidate decreases abnormalities in brain structure and function found in subjects with ADHD.    Atomoxetine, due to its lack of abuse potential, may be preferred in those who are at risk of abusing stimulant medication.  Guidelines on when to use medications vary by country, with the United Kingdom's National Institute for Health and Care Excellence recommending use only in severe cases, while most United States guidelines recommend medications in nearly all cases.

While stimulants and atomoxetine are usually safe, there are side-effects and contraindications to their use.  Stimulants may result in psychosis or mania; however, this is relatively uncommon.   Regular monitoring has been recommended in those on long-term treatment.  Stimulant therapy should be stopped from time to assess for continuing need for medication.  Stimulant medications have the potential for abuse and dependence;  several studies indicate that untreated ADHD is associated with elevated risk of substance abuse and conduct disorders.  The use of stimulants appears to either reduce this risk or have no effect on it.  The safety of these medications in pregnancy is unclear.

Zinc deficiency has been associated with inattentive symptoms and there is evidence that zinc supplementation can benefit children with ADHD who have low zinc levels.  Iron, magnesium and iodine   may also have an effect on ADHD symptoms.  There is evidence of a modest benefit of omega 3 fatty acid supplementation, but it is not recommended in place of traditional medication.

Prognosis

An 8-year follow up of children diagnosed with ADHD (combined type) found that they often have difficulties in adolescence, regardless of treatment or lack thereof. In the US, less than 5% of individuals with ADHD get a college degree, compared to 28% of the general population aged 25 years and older.  The proportion of children meeting criteria for ADHD drops by about half in the three years following the diagnosis and this occurs regardless of treatments used.  ADHD persists into adulthood in about 30–50% of cases.  Those affected are likely to develop coping mechanisms as they mature, thus compensating for their previous symptoms.

Special populations

Adults

It is estimated that between 2–5% of adults have ADHD.  Around half of children with ADHD continue to have ADHD as adults.  Approximately 25% of children continue to experience ADHD symptoms into adulthood, while the remaining 75% experience fewer or no symptoms.  Most adults remain untreated. Many have a disorganized life and use non-prescribed drugs or alcohol as a coping mechanism.  Other problems may include relationship and job difficulties, and an increased risk of criminal activities.  Associated mental health problems include: depression, anxiety disorder, and learning disabilities.

Some ADHD symptoms in adults differ from those seen in children. While children with ADHD may climb and run about excessively, adults may experience an inability to relax or talk excessively in social situations. Adults with ADHD may start relationships impulsively, display sensation-seeking behavior, and be short-tempered. Addictive behavior such assubstance abuse and gambling are common. The DSM-IV criteria have been criticized for not being appropriate for adults; those who present differently may lead to the claim that they outgrew the diagnosis.

Children with high IQ scores

The diagnosis of ADHD and the significance of its impact on children with a high intelligence quotient (IQ) is controversial. Most studies have found similar impairments regardless of IQ, with higher rates of repeating grades and having social difficulties. Additionally, more than half of people with high IQ and ADHD experience major depressive disorder oroppositional defiant disorder at some point in their lives. Generalised anxiety disorder, separation anxiety disorder and social phobia are also more common. There is some evidence that individuals with high IQ and ADHD have a lowered risk of substance abuse and anti-social behavior compared to children with low and average IQ and ADHD. Children and adolescents with high IQ can have their level of intelligence mismeasured during a standard evaluation and may require more comprehensive testing.