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Abnormal Psychology Unit 9: Neurodevelopmental and Neurocognitive Disorders

Neurodevelopmental disorders begin in the developmental period and affect how the brain grows and functions, while neurocognitive disorders involve a decline from a previous level of cognitive functioning, usually later in life. Both groups have strong biological roots and require support that extends to families and caregivers.

Covers: Autism spectrum disorder, Attention-deficit/hyperactivity disorder, Intellectual developmental disorder, Specific learning, communication and tic disorders, Delirium, Major and mild neurocognitive disorders, Alzheimer's disease and other causes of neurocognitive decline

Study guide

Autism spectrum disorder (ASD) involves persistent deficits in social communication and social interaction, shown in all three areas of social-emotional reciprocity, nonverbal communication and developing and maintaining relationships, plus restricted, repetitive patterns of behavior, interests or activities, shown in at least two of four ways: stereotyped movements or speech, insistence on sameness, highly restricted intense interests, and unusual sensory reactivity. Symptoms appear in early development, and severity is rated by the level of support needed (Level 1, 2 or 3). Recent CDC surveillance estimates that roughly 3% of 8-year-olds in the United States have ASD, with boys diagnosed about four times as often as girls. ASD is highly heritable. Large studies have found no link between vaccines and autism, and the 1998 paper claiming one was retracted. Early intensive behavioral intervention, often based on applied behavior analysis, and speech and social skills support improve outcomes.

Attention-deficit/hyperactivity disorder (ADHD) is a persistent pattern of inattention and/or hyperactivity-impulsivity. Children need at least six symptoms in a domain, and people aged 17 and older need at least five, lasting at least six months. Several symptoms must be present before age 12 and in two or more settings, such as home and school. The three presentations are combined, predominantly inattentive and predominantly hyperactive-impulsive. ADHD is highly heritable and linked to differences in dopamine and norepinephrine systems and in frontal-striatal circuits involved in executive functions. Stimulant medications, such as methylphenidate and amphetamines, are effective for many people, and behavioral parent training and classroom management are recommended, especially for young children. Many people continue to have symptoms in adulthood, often with less visible hyperactivity and more restlessness and disorganization.

Intellectual developmental disorder (intellectual disability) involves deficits in intellectual functioning, such as reasoning and learning, and in adaptive functioning across conceptual, social and practical domains, beginning in the developmental period. IQ scores of about 70 or below, two standard deviations under the mean, are typical, but severity (mild, moderate, severe or profound) is now based on adaptive functioning rather than IQ alone. Known causes include Down syndrome (trisomy 21), fragile X syndrome, fetal alcohol spectrum disorders, untreated phenylketonuria and prenatal infections. Specific learning disorder involves persistent difficulty in reading (often called dyslexia), written expression or mathematics well below what is expected for age, not explained by intellectual disability. Tourette's disorder involves multiple motor tics and at least one vocal tic lasting more than a year, starting before age 18.

Neurocognitive disorders involve acquired decline in cognitive domains such as complex attention, executive function, learning and memory, language, perceptual-motor skills and social cognition. Delirium is an acute disturbance of attention and awareness that develops over hours to days, fluctuates during the day and is caused by a medical condition, substance intoxication or withdrawal, or medication. It is common in hospitalized older adults, is often reversible when the cause is treated and should be treated as a medical emergency. Major neurocognitive disorder, formerly called dementia, involves significant cognitive decline that interferes with independence in everyday activities, such as paying bills or managing medications. Mild neurocognitive disorder involves modest decline that requires greater effort or strategies but still allows independence. Clinicians then specify the cause, such as Alzheimer's disease, vascular disease, Lewy bodies or traumatic brain injury.

Alzheimer's disease is the most common cause of major neurocognitive disorder. It is marked by beta-amyloid plaques outside neurons and neurofibrillary tangles of tau protein inside them, with early damage to the hippocampus and loss of acetylcholine neurons. It usually begins with memory problems for new information and progresses gradually. The APOE ε4 allele raises risk for late-onset Alzheimer's, while rare mutations in the APP, PSEN1 and PSEN2 genes cause early-onset forms. Vascular neurocognitive disorder follows strokes or other vascular damage and often progresses in steps. Frontotemporal neurocognitive disorder often begins earlier with personality change, disinhibition or language problems. Neurocognitive disorder with Lewy bodies features fluctuating attention, detailed visual hallucinations and parkinsonian movement. Treatments include cholinesterase inhibitors such as donepezil and the NMDA antagonist memantine for symptoms, newer anti-amyloid antibodies that modestly slow early Alzheimer's, and caregiver support.

Key ideas

• ASD requires deficits in social communication plus restricted, repetitive behaviors, starting in early development.
• ADHD requires symptoms before age 12 in at least two settings, with six symptoms for children and five for those 17 and older.
• Intellectual developmental disorder requires deficits in both intellectual and adaptive functioning, and severity is based on adaptive functioning.
• Delirium is acute, fluctuating and often reversible; major neurocognitive disorder is usually gradual and progressive.
• Major versus mild neurocognitive disorder depends on whether decline interferes with independence.
• Alzheimer's disease involves amyloid plaques, tau tangles and loss of acetylcholine neurons, starting in the hippocampus.
• Vaccines do not cause autism; the claim came from a retracted study.

Formulas and rules

Common mistakes

• Confusing delirium with major neurocognitive disorder; delirium starts suddenly and fluctuates.
• Diagnosing intellectual disability from an IQ score alone without assessing adaptive functioning.
• Forgetting the two-setting and before-age-12 requirements for ADHD.
• Believing that vaccines or 'cold' parenting cause autism.
• Assuming all memory loss in older adults is Alzheimer's disease; depression, delirium, medications and other diseases can also cause it.

Before the test, make sure you can

• Apply the two-part criteria for autism spectrum disorder and explain levels of support.
• Apply ADHD criteria, including age of onset, symptom counts, settings and presentations.
• Explain why intellectual developmental disorder requires adaptive deficits and how severity is set.
• Identify specific learning disorder and Tourette's disorder from a description.
• Distinguish delirium from major neurocognitive disorder by onset, course and cause.
• Distinguish major from mild neurocognitive disorder.
• Describe the brain changes, risk genes and treatments of Alzheimer's disease and the features of other neurocognitive disorders.

Words to know

Autism spectrum disorder

A neurodevelopmental disorder with deficits in social communication and restricted, repetitive behaviors beginning in early development.

Levels of support

ASD severity ratings from Level 1 (requiring support) to Level 3 (requiring very substantial support).

Applied behavior analysis

A behavioral approach that uses reinforcement and structured teaching to build skills, often used in early autism intervention.

ADHD

A persistent pattern of inattention and/or hyperactivity-impulsivity that begins before age 12 and impairs functioning in multiple settings.

Executive functions

Higher-level skills such as planning, working memory, inhibition and flexible thinking, often weaker in ADHD.

Intellectual developmental disorder

Deficits in intellectual and adaptive functioning that begin during the developmental period.

Adaptive functioning

How well a person meets everyday standards of independence in conceptual, social and practical domains.

Down syndrome

A genetic condition caused by an extra copy of chromosome 21 and a common cause of intellectual disability.

Fragile X syndrome

The most common inherited cause of intellectual disability, caused by a mutation on the X chromosome.

Specific learning disorder

Persistent difficulty in reading, writing or math well below expectations for age, not explained by intellectual disability.

Tourette's disorder

Multiple motor tics and at least one vocal tic lasting over a year, beginning before age 18.

Delirium

An acute, fluctuating disturbance of attention and awareness caused by a medical condition, substance or medication.

Major neurocognitive disorder

Significant decline in one or more cognitive domains that interferes with independence in everyday activities.

Mild neurocognitive disorder

Modest cognitive decline that requires extra effort or strategies but does not take away independence.

Beta-amyloid plaques

Clumps of amyloid protein between neurons, a hallmark of Alzheimer's disease.

Neurofibrillary tangles

Twisted fibers of tau protein inside neurons, a hallmark of Alzheimer's disease.

APOE ε4

A gene allele that raises the risk of late-onset Alzheimer's disease but does not guarantee it.

Lewy bodies

Abnormal protein deposits linked to a neurocognitive disorder with fluctuating attention, visual hallucinations and parkinsonism.

Cholinesterase inhibitors

Drugs such as donepezil that slow the breakdown of acetylcholine to ease Alzheimer's symptoms.

Sample practice questions

30 more questions like these, from level 1 to 5, are in the practice set.