What is Attention Deficit Hyperactivity Disorder (ADHD)?

What is ADHD?

ADHD (Attention-Deficit/Hyperactivity Disorder) is a chronic neurodevelopmental disorder characterized by persistent patterns of inattention and/or hyperactivity-impulsivity that cause functional impairment across multiple settings, with symptoms present before age 12 years. 1

Core Symptom Domains

ADHD manifests through two primary symptom clusters that define three distinct clinical presentations 1, 2:

Inattentive Symptoms

• Poor attention to detail and careless mistakes 1
• Difficulty sustaining attention on tasks or activities 1
• Appearing preoccupied with difficulty shifting focus even when directly addressed 1
• Failing to complete tasks due to distraction or getting sidetracked 1
• Organizational challenges resulting in chronic lateness, messiness, and disorganized work 1
• Avoiding tasks requiring sustained mental effort 1
• Frequently losing personal belongings or items needed for tasks 1
• Easy distractibility and forgetfulness 1

Hyperactive-Impulsive Symptoms

• Frequent fidgeting such as tapping or squirming 1
• Difficulty remaining seated for prolonged periods 1
• Inner restlessness or agitation 1
• Being loud and disruptive 1
• Constantly "on the go" with difficulty for others to keep pace 1
• Excessive talking 1
• Interrupting others with difficulty waiting their turn in conversation 1
• Marked impatience, such as difficulty waiting in line 1
• Intruding into others' activities 1

Diagnostic Criteria

To establish an ADHD diagnosis, five or more symptoms from either domain (or both) must persist for at least 6 months in individuals aged 17 years or older (six or more symptoms required for those under 17 years). 1

Critical diagnostic requirements include 1:

• Symptom onset before age 12 years
• Symptoms present in two or more settings (home, work, school)
• Clear evidence that symptoms interfere with or reduce quality of functioning
• Symptoms not better explained by oppositional behavior, other mental disorders, or substance use

Clinical Presentations

ADHD presents in three subtypes 1, 2:

• Predominantly Inattentive Type: Five or more inattentive symptoms but fewer than five hyperactive-impulsive symptoms
• Predominantly Hyperactive-Impulsive Type: Five or more hyperactive-impulsive symptoms but fewer than five inattentive symptoms
• Combined Type: Five or more symptoms from both domains

Adults with ADHD typically present with predominantly inattentive symptoms, as hyperactivity becomes internalized rather than externalized with age. 1, 2

Epidemiology and Clinical Significance

ADHD is the most common neurodevelopmental disorder in children, affecting approximately 8% of children and youth, with 40-60% of cases persisting into adulthood. 1, 3 The estimated adult prevalence is 2.5-5%, with 14.6% of U.S. adults meeting DSM-5 criteria 4, 3.

Chronic Disease Framework

ADHD must be recognized as a chronic condition requiring long-term management following chronic care model and medical home principles. 1, 2 Unlike episodic conditions such as depression, ADHD is a persistent disorder that precedes major life transitions and often becomes more challenging during periods of increased demand, such as pregnancy, parenting, or career advancement 1.

Comorbidity Screening Requirements

Evaluation for ADHD mandates assessment for coexisting conditions, as these commonly occur and alter treatment approaches. 1, 2 Essential screening includes:

• Emotional/behavioral conditions: anxiety, depression, oppositional defiant disorder, conduct disorders 1
• Developmental conditions: learning disabilities, language disorders, other neurodevelopmental disorders 1
• Physical conditions: tics, sleep apnea, seizures 1

Approximately 10% of adults with recurrent depression or anxiety disorders have undiagnosed ADHD, and treatment of mood/anxiety symptoms alone often proves inadequate without addressing the underlying ADHD 1.

Screening and Assessment Tools

Initial screening uses the Adult ADHD Self-Report Scale (ASRS-V1.1) Part A, with a positive screen defined as marking "often" or "very often" for four or more of six questions. 1 Positive screens warrant completion of ASRS Part B and collateral information from someone who knows the patient well to confirm symptom patterns and functional impairment 1.