Source: Abnormal Psychology textbook (University of Florida)
Tags: ADHD, attention deficit, hyperactivity, impulsivity, neurodevelopmental disorder, DSM-5, stimulant medication, Ritalin, Adderall, behaviour therapy, conduct disorder
Difficulty: Intermediate Prerequisites: Basic understanding of the DSM-5 classification system and neurotransmitter function.
Chapter 10 covers disorders tied to brain dysfunction, split into two broad categories: neurodevelopmental disorders (which arise in childhood) and neurocognitive disorders (which arise later in life). ADHD falls into the neurodevelopmental camp alongside autism spectrum disorder, intellectual disability, and learning/communication/motor disorders. Understanding ADHD matters because it is one of the most commonly diagnosed childhood disorders, it frequently persists into adulthood, and it intersects with conduct problems, substance abuse, and mood disorders. You should already be comfortable with basic brain anatomy (prefrontal cortex, cerebellum, striatum) and the role of neurotransmitters such as dopamine and norepinephrine.
ADHD is a neurodevelopmental disorder marked by inattention, hyperactivity, and impulsivity that begins in childhood and persists into adulthood in roughly half of cases. It has strong genetic and neurological underpinnings, is treated primarily with stimulant medication and behaviour therapy, and the combination of both produces the best short-term outcomes.
Attention-deficit/hyperactivity disorder (ADHD)
A neurodevelopmental disorder characterised by persistent patterns of inattention, hyperactivity, and impulsivity that interfere with functioning and development. In simple terms, the child cannot sit still, pay attention, or control impulses in a way that matches their age.
Combined presentation
An ADHD subtype requiring six or more symptoms of inattention and six or more symptoms of hyperactivity-impulsivity. Think of it as the "full package" version of ADHD.
Predominantly inattentive presentation
An ADHD subtype with six or more inattention symptoms but fewer than six hyperactivity-impulsivity symptoms. This is the child who daydreams and loses things but is not necessarily bouncing off the walls.
Predominantly hyperactive/impulsive presentation
An ADHD subtype with six or more hyperactivity-impulsivity symptoms but fewer than six inattention symptoms. This is the child who cannot stop fidgeting and blurts out answers but may still be able to focus on tasks they find engaging.
Conduct disorder
A pattern of behaviour in which children violate social and cultural norms, act in uncaring and antisocial ways, and may abuse drugs or alcohol or break the law. In simple terms, it is when behavioural problems go well beyond the restlessness of ADHD into serious rule-breaking.
Catecholamine neurotransmitters
A class of neurotransmitters including dopamine and norepinephrine that play a role in sustained attention, impulse inhibition, and error processing. These are the chemicals that ADHD medications target.
Behaviour therapy (for ADHD)
A treatment approach that reinforces attentive, goal-directed, and prosocial behaviours while extinguishing impulsive and hyperactive behaviours. Think of it as retraining the reward structure around the child.
All disorders in the DSM-5 relate to brain dysfunction to some degree, but Chapter 10 focuses on disorders with a specifically neurological basis.
ADHD is defined by an inability to sit still and concentrate, a lack of patience, an inability to inhibit impulses, and driven, disorganised behaviour.
The DSM-5 raised the age-of-onset criterion from 7 to 12 years old. Research showed that only about 5% of children who met criteria at age 7 eventually developed ADHD, whereas 95% of those who met criteria by age 12 did. This change likely means ADHD prevalence figures are an underestimate under the older criterion.
ADHD is found across most cultures and ethnic groups. Diagnosis rates in the US are not much higher than in other countries.
Boys are more likely to be diagnosed during childhood and early adolescence.
Girls with ADHD tend to present primarily with inattentive features and display less disruptive behaviour, which may lead to under-identification. This is a commonly tested point.
Children with ADHD typically perform below their intellectual capabilities in school.
About 20–25% of children with ADHD also have a specific learning disorder, compounding academic difficulties.
Peer relationships suffer: children with ADHD may be intrusive, irritable, demanding, and prone to playing by their own rules, leading to social rejection.
Behaviour problems can worsen over development, sometimes reaching the threshold for a conduct disorder diagnosis (especially in the combined presentation subtype).
45–60% of children with ADHD develop a conduct disorder, abuse substances, or violate the law.
Symptoms persist into young adulthood in about 50% of cases.
Adults who had childhood ADHD are at increased risk for antisocial personality disorder, substance abuse, mood and anxiety disorders, marital problems, traffic accidents, legal infractions, and frequent job changes.
An estimated 4.4% of US adults could be diagnosed with ADHD, many of whom were never treated as children.
Brain abnormalities drive the difficulties with attention, planning, following through, and impulse control.
Abnormal activity is found in:
The prefrontal cortex (controls cognition, motivation, and behaviour)
The striatum (working memory and planning)
The cerebellum (motor behaviours)
The cerebral cortex is smaller in volume in children with ADHD, with less connectivity between frontal areas and regions governing motor behaviour, memory, attention, and emotional reactions.
The cortex continues to grow into adolescence, which supports the "neurological immaturity" hypothesis: brains of children with ADHD may be slower to develop, which explains why hyperactivity often declines with age as the brain matures.
ADHD is strongly tied to genetic factors. Antisocial personality disorders, alcoholism, and depression tend to run in the families of children with ADHD.
Genes influencing dopamine, noradrenaline, and serotonin may be abnormal in individuals with ADHD.
Prenatal and birth complications are associated with ADHD: low birth weight, premature delivery, difficult delivery leading to oxygen deprivation.
Maternal substance use during pregnancy (moderate-to-severe drinking, heavy nicotine or barbiturate use) can lead to the behaviour inhibition deficits seen in ADHD. Some researchers argue this link reflects shared genetic risk rather than a direct causal effect.
Lead exposure (e.g. from lead-based paint) has been linked to ADHD in some children.
Diet alone does not cause ADHD, though a healthier diet has been shown to lower hyperactivity symptoms.
Children with ADHD are more likely to come from families that experience frequent disruptions and where parents display aggression, hostility, or substance abuse. Family interaction patterns (particularly in early childhood) influence the course and severity of ADHD, including the development of conduct problems.
Most children with ADHD are treated with stimulant drugs such as methylphenidate (Ritalin), dextroamphetamine (Dexedrine), and mixed amphetamine salts (Adderall).
It seems paradoxical to give a stimulant to a hyperactive child, but 75–85% respond with decreases in demanding, disruptive, and noncompliant behaviour, along with increases in positive mood, goal-directed activity, and quality of social interactions.
Stimulants work by increasing dopamine levels in the brain's synapses, enhancing release and inhibiting reuptake.
Side effects include reduced appetite, insomnia, edginess, gastrointestinal upset, increased frequency of tics, and possible growth stunting.
Stimulants carry a risk of misuse: people may seek them for a high, for resale, or to gain an academic or work edge.
Use of stimulant medication in the US increased substantially in the 1980s and 1990s, with a slower growth rate after the 2000s. There is ongoing debate about whether this reflects better recognition of ADHD or inappropriate overprescription.
Non-stimulant alternatives include atomoxetine, clonidine, and guanfacine, which affect norepinephrine levels. They help reduce tics and improve cognitive performance but carry side effects such as dry mouth, fatigue, dizziness, constipation, and sedation.
Antidepressants (particularly bupropion, which strongly affects dopamine) are sometimes prescribed, especially when depression co-occurs. They are less effective for ADHD than stimulants.
Medication for ADHD has shown primarily short-term success.
Behaviour therapies engage parents and teachers in restructuring rewards and punishments across the child's life.
They help parents break escalation cycles (arguments that lead to more arguments and possibly physical violence).
Children learn to anticipate consequences and make less impulsive choices, and they are taught social skills such as turn-taking, listening, and expressing frustration non-aggressively.
Strong and consistent evidence supports the effectiveness of behaviour therapy in reducing ADHD symptoms.
A major study found that combining stimulants and psychosocial therapy produces greater short-term improvement than either alone:
68% improved with combined treatment
56% improved with medication alone
34% improved with behaviour therapy alone
25% improved with community care alone
Over the longer term, all three treatment groups continued to show fewer ADHD symptoms, but differences between groups diminished. This supports the idea that the combination approach has a stronger short-term advantage, while long-term outcomes converge.
ADHD has a direct impact on educational outcomes and workplace functioning. Understanding the disorder helps explain why some adults struggle with job stability, time management, and relationships despite adequate intelligence, and why early intervention (both medication and behaviour therapy) can alter the trajectory of a child's life.
Students often think ADHD is simply "being hyper." The predominantly inattentive presentation involves no hyperactivity at all, and it is the subtype most commonly missed in girls.
Students sometimes assume that stimulant medication is a paradox that "calms the child down." Stimulants increase dopamine in the prefrontal cortex, improving the brain's ability to regulate attention and behaviour. They do not sedate; they enhance executive control.
Students may believe ADHD is purely a childhood disorder. About half of those diagnosed in childhood continue to meet criteria in young adulthood, and 4.4% of US adults could be diagnosed.
Students often confuse ADHD with conduct disorder. ADHD is about inattention and impulsivity; conduct disorder involves deliberate violation of social norms and rights of others. They can co-occur, but they are distinct diagnoses.
⚠️ Know the three ADHD presentations (combined, predominantly inattentive, predominantly hyperactive/impulsive) and the symptom-count thresholds (six or more in the relevant domain).
⚠️ The age-of-onset change from 7 to 12 in the DSM-5 is a commonly tested detail.
⚠️ Sex differences in presentation (boys more hyperactive, girls more inattentive) and the under-identification of girls are frequent exam topics.
⚠️ The study comparing combined treatment, medication alone, behaviour therapy alone, and community care is a classic exam question. Know the percentages: 68%, 56%, 34%, 25%.
⚠️ Be able to name the key brain regions (prefrontal cortex, striatum, cerebellum) and neurotransmitters (dopamine, norepinephrine) implicated in ADHD.
True or False: The DSM-5 requires ADHD symptoms to be present before age 7.
Fill in the blank: About ___% of children with ADHD continue to show symptoms into young adulthood.
True or False: Girls with ADHD are more likely to present with the predominantly hyperactive/impulsive subtype.
Fill in the blank: Stimulant medications work by increasing levels of ___ in the brain's synapses.
True or False: Behaviour therapy alone was more effective than medication alone in treating ADHD in the major comparison study.
Answers: 1. False (raised to 12). 2. 50%. 3. False (predominantly inattentive). 4. Dopamine. 5. False (medication alone was more effective: 56% vs 34%).
Q: What are the three presentations of ADHD according to the DSM-5, and what symptom thresholds define each?
A: Combined presentation requires six or more symptoms of both inattention and hyperactivity-impulsivity. Predominantly inattentive presentation requires six or more inattention symptoms and fewer than six hyperactivity-impulsivity symptoms. Predominantly hyperactive/impulsive presentation requires six or more hyperactivity-impulsivity symptoms and fewer than six inattention symptoms.
Q: Why was the age-of-onset criterion changed from 7 to 12 in the DSM-5?
A: Research showed that only about 5% of children meeting criteria at age 7 eventually developed ADHD, while 95% of children meeting criteria by age 12 did develop the disorder. The change better captures the true onset window.
Q: Describe two reasons why ADHD may be under-identified in girls.
A: Girls with ADHD tend to present primarily with inattentive features rather than hyperactivity-impulsivity, so their symptoms are less disruptive and less noticeable. This makes them less likely to be referred for evaluation compared to boys, whose hyperactive and disruptive behaviour draws attention.
Q: In the MTA study comparing treatment approaches, what were the improvement rates for combined treatment, medication alone, behaviour therapy alone, and community care?
A: Combined treatment produced improvement in 68% of participants. Medication alone improved 56%. Behaviour therapy alone improved 34%. Community care alone improved 25%.
Q: Name three brain regions implicated in ADHD and the function each controls.
A: The prefrontal cortex (controls cognition, motivation, and behaviour), the striatum (working memory and planning), and the cerebellum (motor behaviours).
Q: How do stimulant medications work to reduce ADHD symptoms?
A: Stimulants increase dopamine levels in the brain's synapses by enhancing dopamine release and inhibiting its reuptake. This improves prefrontal cortex function, leading to better attention regulation and impulse control.
This material connects to mood and anxiety disorders because adults with untreated childhood ADHD are at increased risk for depression, anxiety, and substance abuse. It also links to conduct disorder and antisocial personality disorder, both of which can develop from ADHD, particularly the combined presentation. The neurotransmitter mechanisms (dopamine, norepinephrine) discussed here recur throughout psychopharmacology topics in the course.
ADHD, ADD, attention deficit disorder, hyperactivity, impulsivity, inattention, neurodevelopmental disorder, DSM-5 presentations, combined type, inattentive type, hyperactive-impulsive type, conduct disorder, stimulant medication, methylphenidate, Ritalin, Adderall, Dexedrine, dopamine, norepinephrine, catecholamines, prefrontal cortex, striatum, cerebellum, behaviour therapy, MTA study, comorbidity, antisocial personality disorder