Source: Abnormal Psychology, University of Florida
Tags: ADHD, attention-deficit hyperactivity disorder, inattention, hyperactivity, impulsivity, stimulant medication, Ritalin, Adderall, neurodevelopmental disorder, DSM-5, conduct disorder, dopamine, norepinephrine
Difficulty: Intermediate | Prerequisites: Basic understanding of DSM-5 diagnostic structure, introductory neuroscience (neurotransmitters, brain regions).
Big picture: ADHD is one of several neurodevelopmental disorders, meaning it typically emerges during childhood rather than later in life. It sits alongside autism spectrum disorder, intellectual disability, and learning disorders in that category. The chapter draws a clear line between neurodevelopmental disorders (childhood onset) and neurocognitive disorders (older-age onset, covered separately). Understanding the DSM-5 criteria, the three presentation types, biological underpinnings, and treatment evidence is the core of what you need here.
ADHD is a persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning. The DSM-5 requires symptoms before age 12, across multiple settings, with clear functional impairment. Treatment typically combines stimulant medication with behavioural therapy, though gains from medication alone are short-term.
Neurodevelopmental disorders
Disorders that typically arise during childhood, including ADHD, autism spectrum disorder, intellectual disability, and learning, communication, and motor disorders.
Neurocognitive disorders
Disorders that typically arise in older age, including major and mild neurocognitive disorders and delirium.
Inattention (ADHD)
One of the two core symptom clusters in ADHD. Requires 6+ symptoms (5+ for ages 17+) persisting for at least 6 months at a level inconsistent with developmental stage. In simple terms, this is the "can't focus" side of ADHD: careless mistakes, difficulty sustaining attention, not listening, losing things, forgetfulness.
Hyperactivity-impulsivity (ADHD)
The second core symptom cluster. Same threshold as inattention (6+ symptoms, or 5+ for older adolescents). Think of it as the "can't sit still and can't wait" side: fidgeting, leaving seat, running/climbing inappropriately, talking excessively, blurting out answers, interrupting others.
Combined Presentation
ADHD subtype where both the inattention and hyperactivity-impulsivity criteria are met equally.
Predominantly Inattentive Presentation
ADHD subtype where inattention criteria are met but hyperactivity-impulsivity criteria are not.
Predominantly Hyperactive Presentation
ADHD subtype where hyperactivity-impulsivity criteria are met but inattention criteria are not.
Conduct disorder
A pattern of behaviour that grossly violates social and cultural norms, including being uncaring or antisocial. Relevant here because 45–60% of children with ADHD go on to develop a conduct disorder, abuse substances, or violate the law.
Catecholamines
A class of neurotransmitters including dopamine and norepinephrine. These function abnormally in ADHD and are the target of stimulant medications. Think of them as the brain chemicals responsible for sustained attention, impulse control, and error processing.
Criterion A: Persistent pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development.
Inattention requires 6+ of 8 listed symptoms for 6+ months (5+ for ages 17+).
Hyperactivity-impulsivity requires 6+ of 9 listed symptoms for 6+ months (5+ for ages 17+).
Criterion B: Several symptoms present prior to age 12.
The age threshold was raised from 7 to 12 because 7 failed to capture all individuals; 12 captures roughly 95%.
Criterion C: Symptoms present in two or more settings (home, school, work, social).
Criterion D: Clear evidence the symptoms interfere with or reduce quality of functioning (academic, social, occupational).
Criterion E: Symptoms are not better explained by schizophrenia, another psychotic disorder, or another mental disorder.
Fails to give close attention to details, makes careless mistakes
Difficulty sustaining attention in tasks or play
Does not seem to listen when spoken to directly
Does not follow through on instructions, fails to finish tasks
Difficulty organising tasks and activities (poor time management, missed deadlines)
Avoids or is reluctant to engage in tasks requiring sustained mental effort
Loses things necessary for tasks
Easily distracted by extraneous stimuli (includes unrelated thoughts in older populations)
Forgetful in daily activities
Fidgets with or taps hands and feet
Leaves seat when remaining seated is expected
Runs or climbs inappropriately (restlessness in older adults)
Unable to play or engage in leisure activities quietly
"On the go," as if "driven by a motor"
Talks excessively
Blurts out answers before questions are completed
Difficulty waiting turn
Interrupts or intrudes on others
ADHD begins in childhood by definition.
Children with ADHD often perform below their intellectual capabilities in school. Around 20–25% also have a specific learning disorder.
Poor peer relationships are common: children with ADHD are often rejected for being intrusive, irritable, and demanding.
Behaviour problems can escalate into conduct disorder, particularly in combined presentation.
Symptoms persist into young adulthood in roughly 50% of cases.
Adults diagnosed in childhood face elevated risk for antisocial personality disorder, substance abuse, mood and anxiety disorders, marital problems, traffic accidents, and frequent job changes.
Brain differences: Abnormal activity in the prefrontal cortex (cognition, motivation, behaviour), striatum (working memory, planning), and cerebellum (motor behaviour). The cerebral cortex shows smaller volume and less connectivity between frontal areas and regions governing motor behaviour, memory, attention, and emotional reactions.
Neurological immaturity hypothesis: Children with ADHD may have brains that are slower to develop, which could explain why symptoms often decline with age.
Neurotransmitters: Catecholamines (dopamine and norepinephrine) function abnormally. This is not only relevant to mood but also to sustained attention, inhibition of impulses, and processing of errors. The effectiveness of stimulant drugs targeting these systems supports this model.
Genetics: ADHD is strongly heritable. Siblings are 3–4x more likely to develop it. Twin studies confirm genetic vulnerability. Molecular genetics research points to abnormalities in dopamine, noradrenaline, and serotonin systems.
Prenatal and birth complications: Low birth weight, premature delivery, difficult delivery (oxygen deprivation), maternal use of alcohol, nicotine, or barbiturates during pregnancy.
Families with frequent disruptions, aggressive or hostile parenting, and substance abuse are associated with ADHD.
These factors are often themselves partly driven by genetic effects on impulsivity and cognition.
Family interaction patterns influence the course and severity of ADHD, though they are not considered primary causes.
Stimulant medications (Ritalin, Dexedrine, Adderall)
Increase positive mood, goal-directed behaviour, and quality of social interactions.
Decrease demanding, disruptive, and noncompliant behaviour.
Mechanism: increase dopamine at synapses (by increasing release and/or inhibiting reuptake).
Side effects: insomnia, edginess, gastrointestinal upset, tics, stunted growth, risk of abuse.
Prescriptions rose 200–300% in the 1980s–1990s, then slowed after 2000.
72% of children with ADHD received stimulants, but a majority of those did not meet full criteria, suggesting misprescription.
Gains from medication are short-term: when medication stops, symptoms return.
Norepinephrine-targeting drugs (atomoxetine, clonidine, guanfacine)
Reduce tics and improve cognitive performance.
Side effects: dry mouth, fatigue, dizziness, constipation, sedation.
Antidepressants (e.g. bupropion)
Sometimes prescribed when ADHD co-occurs with depression.
Some positive cognitive effects, but less effective for ADHD specifically.
Behavioural therapies
Engage parents and teachers in modifying rewards and punishments.
Help break cycles of arguments and physical confrontation.
Help children learn to anticipate consequences and reduce impulsivity.
174 studies found behavioural therapy to be highly effective.
Combined treatment (stimulant + psychosocial)
A study of 579 children over 14 months found: 68% of the combined-treatment group reduced ADHD behaviours, compared with 56% for medication alone and 25% for community care alone.
At follow-up, all groups had improved, but all still showed more ADHD symptoms than typical classmates.
Stimulant medications remain the most common front-line treatment for ADHD, but the evidence strongly favours combining them with behavioural therapy. The finding that medication gains vanish when the drug stops is a critical clinical point: treatment planning needs to account for long-term management, not just short-term symptom reduction.
Students often think ADHD is purely a childhood disorder. It persists into adulthood in roughly half of cases, and adults can carry undiagnosed ADHD from childhood.
Students sometimes assume the hyperactive presentation is the "real" ADHD. The predominantly inattentive presentation is equally valid and often underdiagnosed, particularly in girls.
Students may believe stimulant medication "cures" ADHD. Medication manages symptoms while active; it does not produce lasting change once stopped.
Students sometimes conflate ADHD with poor parenting. While family factors influence severity and course, the disorder has strong biological and genetic roots.
⚠️ Know the three ADHD presentations (combined, predominantly inattentive, predominantly hyperactive) and how they map to the DSM-5 criteria.
⚠️ The age-of-onset threshold was raised from 7 to 12 in the DSM-5 because 12 captures 95% of individuals.
⚠️ Be able to explain why stimulant drugs work (dopamine at synapses) and their key limitation (gains are short-term).
⚠️ Know the outcome data from the combined-treatment study: 68% combined, 56% medication alone, 25% community care.
⚠️ Understand the link between ADHD and conduct disorder (45–60%).
True or false: The DSM-5 requires ADHD symptoms to be present before age 7. (False, the threshold is age 12.)
Fill in the blank: The neurotransmitters most implicated in ADHD are ________ and ________. (Dopamine and norepinephrine.)
True or false: Behavioural therapy alone is never effective for ADHD. (False, 174 studies found it highly effective.)
Fill in the blank: Roughly ___% of children with ADHD develop a conduct disorder, abuse substances, or violate the law. (45–60%.)
True or false: ADHD symptoms must be present in at least two settings to meet DSM-5 criteria. (True.)
Q: What are the three ADHD presentation types, and how are they distinguished?
A: Combined presentation (both inattention and hyperactivity-impulsivity criteria met equally), predominantly inattentive (inattention criteria met, hyperactivity-impulsivity not), and predominantly hyperactive (hyperactivity-impulsivity criteria met, inattention not).
Q: Why was the age-of-onset criterion raised from 7 to 12 in the DSM-5?
A: Because the age-7 threshold failed to capture all individuals with ADHD. Raising it to 12 captures approximately 95% of cases.
Q: Explain the mechanism of action of stimulant medications for ADHD.
A: Stimulants increase dopamine activity at synapses by increasing dopamine release and/or inhibiting its reuptake. This addresses the abnormal catecholamine functioning associated with ADHD.
Q: What evidence supports combined treatment (medication + behavioural therapy) over medication alone?
A: A study of 579 children found that after 14 months, 68% of the combined-treatment group showed reduced ADHD behaviours, compared with 56% in the medication-only group and 25% in the community-care group.
Q: What is the key limitation of stimulant medication for ADHD?
A: Gains are short-term. As soon as medication is stopped, symptoms return.
ADHD connects to conduct disorder and antisocial personality disorder (Ch. 10 and personality disorders chapters), as a significant proportion of children with ADHD develop these conditions. The neurotransmitter discussion (dopamine, norepinephrine) ties into broader psychopharmacology and the biological bases of behaviour. The role of genetic vulnerability links to the diathesis-stress model covered in earlier chapters.
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