Attention-deficit/hyperactivity disorder (ADHD)

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Attention-deficit/hyperactivity disorder (ADHD) is defined as a behavioral disorder of childhood onset (by the age of 7 years) characterized by symptoms of inattentiveness and impulsivity/hyperactivity. Based on the type of symptoms that predominate, ADHD is classified as following:
 Combined type: both inattention and hyperactivity/impulsivity symptoms are present
 Predominantly inattentive subtype
 Predominantly hyperactive/impulsive subtype
 Not otherwise specified (NOS): individuals presenting with atypical features

Sex/Age Ratio:
• ADHD is a developmental disorder that requires an onset of symptoms before age 7 years. After childhood, symptoms may persist into adolescence and adulthood, or they may ameliorate or disappear.

• The percentages in each group are not well established, but at least an estimated 15-20% of children with ADHD maintain the full diagnosis into adulthood. As many as 65% of these children will have ADHD or some residual symptoms of ADHD as adults.
• The prevalence rate in adults has been estimated at 2-7%. The prevalence rate of ADHD in the adult general population is 4-5%.

• In children, ADHD is 3-5 times more common in boys than in girls. Some studies report an incidence ratio of as high as 5:1. The predominantly inattentive type of ADHD is found more commonly in girls than in boys.
• In adults, the sex ratio is closer to even.


 Incidence in school-age children is estimated to be 3-7%.

 ADHD prevalence varies by race and ethnicity, with Mexican children having consistently lower prevalence compared with other racial or ethnic groups.
 Prevalence of ADHD increases to 10% for children with family incomes less than 100% of the poverty level and to 11% for those with family income from 100-199% of the poverty level.

 As such no single etiology has been identified for ADHD. ADHD is a heterogeneous condition currently thought to result from a complex interaction between the psychosocial stressors, environmental factors, neuro-chemical/ neuro-anatomical factors, familial and genetic factors.

Psychosocial Factors
• Psychosocial stressors are not thought to cause ADHD
• ADHD symptom and co morbidity related to levels of stress and psychosocial adversity
• Higher levels of stress and psychosocial adversity in children with ADHD and co morbid anxiety or mood disorders than in children with ADHD alone.
• Children with ADHD and no co morbidities had levels of psychosocial stress no different than controls.

Environmental Factors
Pregnancy and Delivery Complications
These factors include:
• Prenatal and delivery complications
• Prenatal or perinatal brain injury
• Prematurity
• Small for gestational age
• Low birth weight
The following factors have not been supported by research as having an association with development of ADHD.
• Allergic or toxic reactions to food additives
• Refined sugar

Environmental Factors
• Exposure to Toxins
• Mercury, manganese, lead
• Polychlorinated bi-phenyls

How to Cite this Page

MLA Citation:
"Attention-deficit/hyperactivity disorder (ADHD)." 30 Mar 2017

• Fetal exposure to alcohol
• Fetal exposure to maternal smoking
• Chaotic family environments
• Low social class

• 20% of children with traumatic brain injury have core symptoms
• These children also have higher levels of stress and adversity
• ADHD may be a risk for traumatic brain injury
• Genetic, traumatic and psychosocial factors related to TBI

Neurological Models of ADHD
Currently there are 4 broad theories:
• A dysfunction of selective attention and hyperactivity -dopamine system
• A disturbance in the noradrenergic system leading to excessive arousal -NE
• Impaired behavioral inhibition
• Deficits in limbic circuitry in conjunction with deficits in information processing leading to a deficient reward system.

Neurochemical Theories
 Catecholamine dysfunction is currently thought to play a major role in ADHD.

 Studies specifically implicate dopamine and nor epinephrine.

 Medical therapies are directed at these 2 neurotransmitters.

• Methylphenidate (Ritalin) -Dopamine
• Atomoxetine (Strattera)-NE

Neuroanatomical Factors
• Loss of normal brain asymmetry
• Total cerebral volume is ~3% smaller
• Right prefrontal cortex, caudate nucleus and Globus pallidus to be smaller
• These areas modulate attention, stimulus processing, executive function and impulsivity
• Normalize by mid-adolescence, however, decreased cerebellar volume continues.

Genetic Factors
• Highly heritable genetic disorder
• Polygenic.
• Monozygotic twin studies show 55%-90% concordance rate
• Many of the genes are in the catecholamine system
• Nature of genetic risk and mode of inheritance is still largely unknown.


These include:

• Impulsivity, e.g. acting before thinking, quick responses, poor judgment
• Difficulty in feeling motivated
• Impaired abilities for attention and concentration; distractibility
• Difficulties organizing tasks and activities
• Restlessness and hyperactivity
• Impaired emotional controls
• Associated features:
Learning disabilities
Low self-esteem


• Developmental history
• Medical history
• Behavioral history
• Educational history

 Using well tested diagnostic interview, based primarily on DSM-IV criteria taken by licensed, qualified mental health professionals.


• Methylphenidate: Ritalin, Concerta, Focalin, Medadate CD, Daytrana

• Amphetamine: Dexedrine, Adderall, Vyvanse, Atomoxetine (Strattera)

• Other Nor epinephrine Reuptake Inhibitors (Bupropion) Effexor

• Anti-Hypertensives: Guanfacine and Clonidine

Non pharmacologic therapies

Environmental modifications
 Identify and minimize or avoid distractions
 Shop in smaller stores
 avoid working in cubicles
 Practice organization by assigning specific
 Storage spaces for bills, keys etc.
Helpful external aids
• calendar with day planner
• personal tape recorder
• Sticky note pads
• Checklists
• Reminder alarms

Behavior Techniques

Clinical guidelines and pearls:

 ADHD is a heterogeneous disorder with a strong neurobiological basis that afflicts millions of individuals of all ages worldwide.
 Although the stimulants remain the mainstay of treatment for this disorder, a new generation of nonstimulant drugs is emerging that provides a viable alternative for patients and families.
 It is essential to apply a careful differential diagnosis in the assessment of the ADHD patient that considers psychiatric, social, cognitive, educational, and medical/neurological factors that may contribute to the individual's clinical presentation.
 Realistic expectations of interventions, precise definition of target symptoms, and careful assessment of the potential risks and benefits of each type of intervention for such patients are the major ingredients of successful treatment.
 Poor performance at school and work can lead to development of other co-existent psychiatric illness among these patients.
 ADHD is one of the major clinical and public health problems in the United States in terms of morbidity and disability in children and adolescents. It is estimated to affect at least 5% of school-age children. Its impact on society is enormous in terms of financial cost, the stress to families, the impact on schools, and the damaging effects on self-esteem.

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