14.2 Attention-Deficit/Hyperactivity Disorder (ADHD)

Overview of Attention-Deficit/Hyperactivity Disorder (ADHD)

ADHD is a neurodevelopmental disorder defined by persistent patterns of inattention and/or hyperactivity-impulsivity that interfere with functioning or development. Symptoms must be present before age 12 and show up in at least two settings (home, school, work) to meet diagnostic criteria. This distinction matters because it separates ADHD from situational attention problems that only appear in one context.

Primary Symptoms of ADHD

ADHD symptoms fall into two clusters: inattention and hyperactivity-impulsivity. A person can have symptoms from one or both clusters.

Inattention symptoms involve:

• Difficulty sustaining focus on tasks or activities
• High distractibility by unrelated stimuli
• Failing to follow through on instructions or complete tasks
• Avoiding or being reluctant to engage in mentally demanding activities
• Frequently losing items needed for tasks (keys, homework, tools)
• Forgetfulness in daily routines

Hyperactivity-impulsivity symptoms include:

• Fidgeting, squirming, or tapping hands and feet
• Trouble staying seated when expected to
• Excessive running or climbing in children; a persistent sense of restlessness in adolescents and adults
• Difficulty engaging in quiet activities
• Feeling constantly "on the go" or "driven by a motor"
• Excessive talking, blurting out answers, or interrupting others
• Struggling to wait for one's turn

The DSM-5 requires at least six symptoms from a cluster (five for adults 17+) persisting for at least six months to qualify for diagnosis.

Subtypes of ADHD

• Predominantly Inattentive Type (ADHD-PI): Primarily inattention symptoms. These individuals may appear sluggish, daydreamy, or easily confused. They're often underdiagnosed because they don't display the disruptive behavior people typically associate with ADHD.
• Predominantly Hyperactive-Impulsive Type (ADHD-HI): Mainly hyperactivity-impulsivity symptoms. These individuals appear restless, fidgety, and disruptive. This subtype is more common in young children and relatively rare in adults.
• Combined Type (ADHD-C): Meets criteria for both inattention and hyperactivity-impulsivity. This is the most commonly diagnosed subtype.

Symptom presentation can shift over time. For example, a child diagnosed with Combined Type may show fewer hyperactive symptoms in adolescence and be reclassified as Predominantly Inattentive. Hyperactivity tends to decrease with age, while inattention symptoms often persist.

Etiology and Impact of ADHD

Contributing Factors

ADHD arises from an interaction of biological, psychological, and environmental factors. No single cause explains every case, but genetics play the largest role.

Biological factors:

• Genetic influences: ADHD is highly heritable, with twin studies estimating heritability at roughly 70–80%. Multiple genes are involved, many of which affect dopamine signaling.
• Neurochemical imbalances: Dysregulation in the dopamine and norepinephrine systems is central to ADHD. These neurotransmitters are critical for attention, motivation, and impulse control, which is why medications targeting them are effective.
• Brain structure and function: Neuroimaging studies show reduced volume and lower activity in the prefrontal cortex (responsible for executive functions) and the striatum (involved in reward processing). Maturation of the prefrontal cortex is also delayed by roughly 2–3 years in children with ADHD.

Psychological factors:

• Executive functioning deficits in working memory, inhibitory control, and cognitive flexibility. These aren't just symptoms of ADHD; they help explain why people with ADHD struggle with planning, organization, and task completion.
• Difficulties with emotional regulation and motivation. Many individuals with ADHD experience intense emotional reactions and have trouble sustaining effort on tasks that aren't immediately rewarding.

Environmental factors:

• Prenatal exposure to alcohol or tobacco
• Low birth weight and premature birth
• Early childhood exposure to environmental toxins, particularly lead
• Family dysfunction and adverse childhood experiences (these don't cause ADHD on their own, but they can worsen symptom severity)

Impact on Functioning

ADHD affects multiple life domains, and its consequences tend to compound over time if untreated.

Academic functioning:

• Difficulty completing assignments, studying effectively, and staying organized
• Lower grades and higher rates of academic underachievement relative to measured ability
• Increased risk of school dropout

Social functioning:

• Trouble maintaining friendships and romantic relationships
• Impaired social skills, partly because impulsivity leads to interrupting, missing social cues, or reacting too intensely
• Higher rates of peer rejection and social isolation

Occupational functioning:

• Difficulty maintaining consistent employment
• Lower job performance and productivity
• Increased risk of workplace accidents and injuries

Treatment of ADHD

Treatment for ADHD typically works best as a multimodal approach, combining medication with behavioral and psychosocial interventions. The right combination depends on the individual's age, symptom severity, and specific functional impairments.

Pharmacological Treatments

1. Stimulant medications (methylphenidate, amphetamines like Adderall)

   • These are the first-line treatment and are effective for roughly 70–80% of individuals with ADHD
   • They work by increasing dopamine and norepinephrine availability in the brain, particularly in the prefrontal cortex
   • Effects include improved attention, reduced hyperactivity, and better impulse control
   • Common side effects include decreased appetite, insomnia, and increased heart rate

2. Non-stimulant medications (atomoxetine, guanfacine, clonidine)

   • Used when stimulants are ineffective, cause intolerable side effects, or when there's a risk of substance misuse
   • Atomoxetine is a selective norepinephrine reuptake inhibitor; guanfacine and clonidine activate alpha-2 adrenergic receptors
   • These medications tend to have a slower onset of action compared to stimulants

Non-Pharmacological Treatments

1. Behavioral therapy: Teaches concrete strategies for managing symptoms, such as positive reinforcement systems, time management techniques, and organizational skills training. For children, this often involves structuring the environment to support desired behaviors.

2. Cognitive-behavioral therapy (CBT): Targets maladaptive thought patterns (like "I'll never be able to finish this") and builds coping strategies and problem-solving skills. CBT is especially useful for adolescents and adults who have developed negative self-beliefs from years of ADHD-related struggles.

3. Parent training and education: Equips parents with strategies for managing their child's behavior and creating a structured, supportive home environment. This is considered a first-line treatment for preschool-aged children with ADHD, often before medication is introduced.

4. Educational interventions and accommodations: These include individualized education plans (IEPs) or 504 plans, classroom modifications (preferential seating, extended test time), and assistive technology. The goal is to reduce barriers to learning rather than expecting the student to simply "try harder."