CH-14-Neurodevelopmental Disorders – Comprehensive Study Notes

Overview of Neurodevelopmental Disorders

• ALL psychiatric conditions change across the life-span, but DSM-5 reserves the term “neurodevelopmental” for disorders whose core symptoms are neurologically based and emerge in childhood.
  • Includes: Attention-Deficit/Hyperactivity Disorder (ADHD), Specific Learning Disorder (SLD), Autism Spectrum Disorder (ASD), Intellectual Disability (ID), and several Communication & Motor Disorders.
• Developmental Psychopathology perspective:
  • Skills normally appear in a sequential pattern; disruption of an early skill (e.g., joint attention) affects later skills (e.g., language, social reciprocity).
  • Biological and psychosocial factors continuously interact—course and prognosis are not predetermined.
  • Risk of mistaking normal developmental stages (e.g., echolalia in toddlers) for pathology.
• APA Undergraduate Psychology Goals addressed in the chapter include: scientific reasoning, operational description of problems, identifying antecedents & consequences, and applying principles to everyday life.

Attention-Deficit/Hyperactivity Disorder (ADHD)

• Core symptom clusters (DSM-5):
  • Inattention (e.g., careless mistakes, losing materials, difficulty sustaining focus).
  • Hyperactivity (fidgeting, inability to stay seated, "on the go").
  • Impulsivity (blurting answers, intrusive, difficulty waiting turn).
  • Diagnosis requires ≥6 symptoms from cluster A1 and/or A2 for ≥6 months (≥5 for ages \ge 17); onset <12 yrs; impairment in ≥2 settings.
  • Subtypes/“presentations”: • Predominantly Inattentive • Predominantly Hyperactive/Impulsive • Combined.
• Case Illustration – Danny: 9-yr-old whose impatience, classroom roaming, and impulsive sport play reflect combined presentation.
• Epidemiology
  • Worldwide child prevalence ≈ 5.2\% (Polanczyk et al.).
  • U.S. parent-report (2011-2012): 11\% of 4-17-yr-olds labelled.
  • Male : Female diagnosis ratio \approx 2{-}3:1; girls show more internalizing (anxiety, depression).
• Course & Outcome
  • Symptoms detectable ~3{-}4 yrs.
  • Persist through adolescence in ~50\%; adult sequelae: risky driving, STIs, lower educational attainment, substance use, ASPD.
• Comorbidity / Diagnostic overlap: ODD, Conduct Disorder, Bipolar Disorder.
• Etiology
  • Genetics: high heritability; implicated genes include dopamine D4 receptor, dopamine transporter (DAT1), D5 receptor; copy-number variants (CNVs).
  • Brain/Neurochemistry: total brain volume ↓ 3{-}4\%; fronto-striatal circuits implicated; stimulant meds may have "growth-enhancing" effect on cortical maturation.
  • Gene × Environment: DAT1 + prenatal smoking; also maternal stress, alcohol, low birth weight.
  • Food additives/pesticides produce small effect on hyperactivity.
• Treatment
  • Psychosocial: Parent/teacher behavioral management, contingency programs, social-skills training, CBT for adults.
  • Pharmacological: Stimulants (methylphenidate, amphetamine formulations), non-stimulants (atomoxetine, guanfacine, clonidine, certain antidepressants). Concerns—growth suppression, insomnia, abuse potential.
  • Multimodal Treatment Study (MTA): 14-mo RCT showed meds ± behavioral > community care; combined slightly better for broader domains.
  • Precision medicine/psychopharmacogenetics: ADRA2A genotype predicts methylphenidate response.

Specific Learning Disorder (SLD)

• Definition (DSM-5): Academic skills \ll age & cognitive level for ≥6 mo despite targeted intervention; begins during school years; not due to sensory deficit or inadequate instruction.
• Specifier Domains & Symptom Examples
  • Reading: slow/incorrect word reading, poor comprehension (often labelled "dyslexia").
  • Written Expression: spelling, grammar, organization.
  • Mathematics: number sense, fact fluency, calculation, reasoning ("dyscalculia").
• Diagnostic Shift
  • DSM-IV used IQ-achievement discrepancy (≥2 SD); DSM-5 favors Response to Intervention (RTI)—failure to improve with evidence-based instruction.
• Prevalence
  • 5{-}15\% of school-age children worldwide; domain-specific: reading 7 %, spelling 9 %, arithmetic 5 % (German sample).
  • U.S. service data: 6.5 million (ages 3-21) receive SLD supports; higher identification in wealthier states; racial disproportionality (2.6 % Black vs 1 % White serviced).
• Case – Alice: Above-average IQ, severe reading comprehension problems, compensated by reading aloud; diagnosed in college.
• Etiology
  • Genetic: Multiple genes across chromosomes 1,2,3,6,11,12,15,18; shared liability across reading/math/writing.
  • Brain: Reading—differences in left hemisphere (Broca, parietotemporal, occipitotemporal); Math—intraparietal sulcus.
  • Environment: Home literacy, quality of instruction can buffer genetic risk.
• Communication & Motor Disorders (Table 14.1)
  • Childhood-onset Fluency Disorder (stuttering)
  • Language Disorder
  • Social (Pragmatic) Communication Disorder (new DSM-5, ASD-like social deficits without repetitive behaviors)
  • Tourette’s Disorder (motor & vocal tics)
• Intervention
  • Educational: Direct Instruction (scripted, mastery-based), skills & strategy training.
  • Neural Plasticity Evidence: fMRI shows normalization of reading networks after 8-week intensive training.
  • Assistive tech: Computerized language, speech-feedback, eye-tracking supports.

Autism Spectrum Disorder (ASD)

• DSM-5 Consolidation: Combines Autistic Disorder, Asperger’s, Childhood Disintegrative Disorder, PDD-NOS under ASD; Rett Syndrome coded as ASD "associated with MeCP2 mutation".
• Diagnostic Dyad
  1. Deficits in social communication & interaction — must include deficits in reciprocity, non-verbal communication, developing/maintaining relationships.
  2. Restricted, repetitive behaviors/interests (RRBs) — ≥2 of stereotyped motor/speech, insistence on sameness, fixated interests, hyper/hypo-reactivity to sensory input.
  • Symptoms present early; impair functioning.
  • Severity Levels: Level 1 ("requiring support"), Level 2 ("substantial support"), Level 3 ("very substantial support").
• Illustrative Cases
  • Timmy: Severe language delay, solitary play, hand-flapping, lining up blocks; diagnosis delayed until age 7, later institutionalized.
  • Amy: 3-yr-old, no speech, repetitive lint-dropping ritual, butter-eating; likely Level 3 ASD.
• Epidemiology
  • Current U.S. prevalence 1 in 68 eight-year-olds; male:female ≈ 4.5:1.
  • ID co-occurs in ~31\%; savant skills in ~1/3 but absent in most severe ID.
• Etiology
  • Genetics: Strong but complex; sibling recurrence ≈20\%; many genes of small effect; CNVs; oxytocin receptor gene studied.
  • De-novo mutations & parental age: Paternal age ≥40 or maternal age ↑ risk (possibly due to gamete mutations).
  • Neurobiology: Early amygdala enlargement → cortisol neurotoxicity → fewer neurons; lower blood oxytocin.
  • Vaccines/Thimerosal: Large studies show no link; non-vaccination ↑ measles/mumps resurgence.
• Psychosocial Models (historical): "Refrigerator mothers," lack of self-awareness—all discredited.
• Intervention
  • Early Intensive Behavioral Intervention (EIBI): 20-40 hr/week of one-to-one ABA (e.g., Lovaas model); teaches imitation, language, joint attention; fMRI evidence of brain "normalization".
  • Naturalistic Developmental Behavioral Interventions: Incidental teaching, pivotal response training, milieu teaching; embed instruction in play and routines.
  • Augmentative/Alternative Communication (AAC): Picture Exchange Communication System (PECS), speech-output tablets.
  • School-age & Adolescents: Social-skills groups, perspective-taking, managing comorbid anxiety/ADHD.
  • Medications: No cure; antipsychotics (e.g., risperidone) and SSRIs may ↓ irritability/agitation.
  • Outcome Predictors: Higher IQ & early functional speech → better adult independence.

Intellectual Disability (ID) – a.k.a. Intellectual Developmental Disorder

• Diagnostic Triad (DSM-5)
  1. Deficits in intellectual functioning (reasoning, problem-solving, planning) confirmed by testing (IQ ≈ \le 70 ±5).
  2. Deficits in adaptive functioning across conceptual, social, & practical domains.
  3. Onset during developmental period (
• Severity – DSM vs AAIDD
  • DSM-5: Mild, Moderate, Severe, Profound (based on adaptive functioning, NOT IQ alone).
  • AAIDD: Intermittent, Limited, Extensive, Pervasive supports required.
• Prevalence & Course
  • Global prevalence 1{-}3\%; ~90\% are Mild.
  • Flynn Effect: Rising population IQs ⇒ re-normalization of test norms can shift individuals above/below ID threshold.
• Etiological Categories
  • Environmental: deprivation, abuse, neglect.
  • Prenatal: maternal disease, teratogens (e.g., alcohol → Fetal Alcohol Syndrome), malnutrition.
  • Perinatal: anoxia, birth complications.
  • Postnatal: infections, TBI, severe social isolation.
• Genetic & Chromosomal Disorders
  • Dominant: Tuberous Sclerosis (1/30,000).
  • Recessive: Phenylketonuria (PKU) – cannot metabolize phenylalanine; treat with lifelong diet (hence “Phenylketonurics” label on diet soda).
  • X-linked: Lesch-Nyhan (self-injury + spasticity); Fragile X (males > females, large ears, gaze avoidance).
  • Trisomy 21 (Down Syndrome): extra 21st chromosome; risk rises with maternal age (e.g., age 20: 1/2000; age 35: 1/500; age 45: 1/18). Early Alzheimer-type dementia common.
  • Unknown origin: ~30\%; emerging evidence implicates de-novo CNVs, mitochondrial defects.
• Assessment & Screening
  • Prenatal: Amniocentesis, Chorionic Villus Sampling, non-invasive cell-free fetal DNA blood tests.
• Intervention
  • Behavioral: Task analysis & chaining for self-care; reinforcement; functional communication training; positive behavioral supports for aggression/self-injury.
  • Education & Employment: Inclusive schooling, community-based instruction, supported employment; cost-effective.
  • AAC & Tech: Eye-gaze boards, speech-generating devices.
  • Prevention: Genetic counseling, maternal health, toxin avoidance, early enrichment (e.g., Head Start, Abecedarian Project).

Communication & Motor Disorders (DSM-5 Table 14.1)

• Childhood-Onset Fluency Disorder (Stuttering) – \approx 2× boys; onset ≤6 yrs; 80\% remit; regulated-breathing & altered auditory feedback helpful.
• Language Disorder – 10-15 % <3 yrs; boys ≫ girls; may self-correct; middle-ear infections possible factor.
• Social (Pragmatic) Communication Disorder – rising diagnosis; individualized social-skills training.
• Tourette’s Disorder – tics in 1-10/1000 children; multiple vulnerability genes; habit reversal & relaxation training.

Prevention & Ethics

• Early identification & intervention (behavioral + medical) produce best outcomes (e.g., EIBI for ASD; early reading programs for SLD).
• Gene-editing / prenatal therapy research (e.g., fragile X mouse mGluR blockers) raises privacy, consent, and discrimination concerns.
• Public health (lead abatement, anti-smoking campaigns, vaccination) and enrichment programs (Head Start) are large-scale preventive strategies.

Key Numerical/Statistical References (Sample)

• ADHD worldwide prevalence \approx 5.2\%; U.S. parent-report 11\%.
• SLD prevalence 5{-}15\%; reading disorder 7\% general population.
• ASD prevalence 1/68; male:female \approx 4.5:1.
• Fragile X: 1/4000 males; 1/8000 females.
• Down Syndrome risk by maternal age: 20 yrs =1/2000; 35 yrs =1/500; 45 yrs =1/18.

Ethical, Philosophical & Practical Implications

• Balancing early gene screening with autonomy and potential stigmatization.
• Neurodiversity movement challenges pathologizing mild ASD ("Aspies"), advocates viewing differences as variation not disorder.
• Service eligibility tied to diagnostic criteria (e.g., DSM-5 ASD consolidation) may influence access to resources.
• Medication use in children (stimulants, antipsychotics) necessitates monitoring for abuse, side-effects, and long-term outcomes.

Connections to Foundations & Real-World Relevance

• Learning principles (classical & operant conditioning) underpin behavioral interventions across disorders.
• Executive-function deficits link ADHD, SLD, and some presentations of ASD.
• Public policy (IDEA, inclusive education, disability rights) directly shapes treatment environments.
• Lifespan perspective: early disruptions reverberate into adulthood affecting employment, relationships, and health.