Neurodevelopmental Disorders (College Board AP® Psychology): Study Guide

Autism spectrum disorder (ASD)

• Neurodevelopmental disorders emerge during childhood or adolescence, before full brain maturation

  • They are defined by whether development follows typical age-related patterns or shows significant deviation

• Two neurodevelopmental disorders are:

  • Autism spectrum disorder (ASD)

  • Attention-deficit hyperactivity disorder (ADHD)

Symptoms of ASD

• Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by:

  • difficulties in social communication and interaction, e.g.

    • difficulty interpreting social cues (e.g. facial expressions, tone)

    • reduced sharing of emotions or interests

    • difficulty initiating or maintaining interactions

    • difficulty forming relationships

  • restricted, repetitive patterns of behavior, interests, or activities, e.g.

    • repetitive movements or speech (e.g. hand flapping)

    • strong preference for routine; distress at change

    • highly focused, intense interests

    • atypical sensory responses (over- or under-sensitivity)

ASD as a spectrum

• ASD is described as a spectrum, meaning that it encompasses a wide range of presentations, from very mild to very severe:

  • Very mild: An individual may have subtle social difficulties but can live independently

    • E.g. finding small talk challenging, preferring routines, having focused interests

  • Moderate: An individual may show more noticeable social communication difficulties, rely heavily on routines, and need support in education or work settings

    • E.g. difficulty holding conversations, becoming very distressed by changes to daily routines, and struggling to make or maintain friendships

  • Very severe: An individual may have limited or no verbal communication, significant difficulty understanding social interaction, intense repetitive behaviors, and require substantial, lifelong support

    • E.g. non-verbal or using very limited speech, not responding to social cues, engaging in repetitive movements, and needing full-time care for daily activities such as eating or dressing

Possible causes of ASD

• ASD has no single cause, rather it results from multiple interacting factors:

  • Genetic: ASD has a strong heritable component; identical twin concordance rates are substantially higher than for fraternal twins, indicating that genes increase susceptibility to ASD

  • Physiological: differences in brain structure and connectivity in individuals with ASD, particularly in brain regions involved in social processing

  • Environmental: prenatal influences (e.g. maternal infection, medication, parental age) are associated with increased risk; postnatal environmental factors may also play a role

• There is no evidence that vaccines cause ASD

  • This claim is based on fraudulent, discredited research and no subsequent research has found any causal relationship

Attention-deficit hyperactivity disorder (ADHD)

Symptoms of ADHD

• ADHD is a neurodevelopmental disorder characterized by persistent patterns of:

  • inattention

  • and/or hyperactivity-impulsivity

• These symptoms must:

  • interfere with the individual's functioning at home, at work or school, and in relationships

  • be present before the age of 12 for diagnosis

• ADHD has three presentations:

  • Predominantly inattentive

  • Predominantly hyperactive-impulsive

  • Combined presentation (most common)

• Inattention symptoms include:

  • difficulty sustaining attention on tasks, especially those that are not immediately rewarding

  • being easily distracted by external stimuli or unrelated thoughts

  • frequently loses things (e.g. keys, phone, schoolbooks)

  • difficulty completing tasks

  • appearing not to listen

  • avoiding tasks requiring sustained mental effort

    • E.g. a student with ADHD starts homework but repeatedly becomes distracted and does not finish it

• Hyperactivity-impulsivity symptoms include:

  • fidgeting or restlessness (e.g. tapping hands or feet, or squirming in seat)

  • difficulty remaining seated

  • excessive talking

  • blurting out answers before questions are complete

  • difficulty waiting turns

  • interrupting others

    • E.g. a young child with ADHD cannot stay seated during class, interrupts the teacher repeatedly, and acts without thinking

Possible causes of ADHD

• Like ASD, ADHD results from multiple interacting factors:

  • Genetic factors: ADHD is highly heritable, as it runs strongly in families. Genetic research shows that it is linked to genes affecting dopamine

  • Physiological factors: ADHD is associated with differences in brain development, particularly in regions involved in attention, executive function, and impulse control (e.g. the prefrontal cortex)

  • Environmental factors: prenatal exposure (e.g tobacco smoke, alcohol), low birth weight, early stressors and premature birth are associated with increased ADHD risk

• ADHD may be underdiagnozed in girls, as they more often present with inattentive symptoms, which are less disruptive