What are the core symptoms of attention-deficit/hyperactivity disorder?

Core Symptoms of ADHD

ADHD is characterized by three core symptom domains—inattention, hyperactivity, and impulsivity—which must cause functional impairment in at least two settings (home, school, work, or social environments) to meet diagnostic criteria. 1

Primary Symptom Categories

Inattentive Symptoms

• Difficulty sustaining attention during tasks or play activities, appearing not to listen when spoken to directly 1
• Careless mistakes due to poor attention to detail in schoolwork, work tasks, or other activities 2
• Avoidance or dislike of tasks requiring sustained mental effort (homework, paperwork, lengthy forms) 1
• Frequent loss of items necessary for tasks and activities (school materials, wallets, keys, phones) 1
• Organizational difficulties with tasks, activities, materials, and time management 1, 2
• Failure to follow through on instructions and difficulty completing tasks 2
• Easy distractibility by extraneous stimuli 2
• Forgetfulness in daily activities 2

Hyperactive Symptoms

• Fidgeting with hands or feet, or squirming in seat 1
• Inability to remain seated in situations where sitting is expected 2
• Running or climbing in inappropriate situations (in adolescents/adults, may manifest as subjective feelings of restlessness) 1
• Difficulty engaging quietly in leisure activities 2
• Being "on the go" or acting as if "driven by a motor" 1
• Excessive talking 2

Impulsive Symptoms

• Blurting out answers before questions are completed 2
• Difficulty waiting one's turn 2
• Interrupting or intruding on others' conversations or activities 1
• Impulsive decision-making without considering consequences 1

Diagnostic Thresholds

Children under 17 years require at least 6 symptoms from either the inattentive or hyperactive/impulsive category (or both), while adults 17 years and older require at least 5 symptoms. 1, 2

• Symptoms must persist for at least 6 months 1, 2
• Symptoms must have been present before age 12 years 1, 2
• Impairment must occur in at least 2 settings (e.g., home and school, work and social situations) 1, 2
• Clear evidence of functional impairment in social, academic, or occupational functioning must be documented 1

Age-Specific Presentations

Preschool Children (Ages 4-5)

• Extreme hyperactivity and inability to sit during structured activities are most prominent 1
• Marked distractibility and difficulty finishing simple tasks 2
• Diagnosis is more challenging due to developmental variability 1

School-Age Children (Ages 6-11)

• Symptoms become most apparent in structured settings like classrooms 1
• Disruptive classroom behavior and difficulty completing homework or classwork are common manifestations 1, 2
• Careless mistakes in schoolwork become more evident 2

Adolescents (Ages 12-18)

• Overt hyperactivity declines but internal restlessness persists 1, 2
• Inattentive symptoms become more prominent and problematic 1, 2
• Hyperactive presentation shifts to more subtle manifestations including impulsive decision-making 1
• Adolescents frequently underestimate the severity of their symptoms and related impairments 1, 2

Adults

• Predominantly inattentive presentation rather than hyperactive symptoms 1, 3
• Poor attention to detail and difficulty maintaining concentration are typical 1, 2
• Significant organizational difficulties managing tasks, materials, and time 1, 2
• Residual hyperactive-impulsive features such as fidgeting, inability to sit still, and internal agitation may persist 2

Critical Diagnostic Pitfalls to Avoid

Relying solely on self-report is a critical error, particularly in adolescents and adults who often lack insight into their symptoms or may underestimate their severity. 4, 1

• Multiple observers across different settings are mandatory (parent/guardian reports, teacher reports, direct observation) 1, 2
• For adolescents and adults, collateral history from parents or school records is necessary to document childhood manifestations before age 12 4, 1
• Variability in ratings between settings is expected and can provide valuable clinical insight 4

Essential Comorbidity Screening

The majority of individuals with ADHD meet criteria for at least one additional psychiatric disorder, making systematic screening essential. 2

Common Comorbidities

• Oppositional defiant disorder and conduct disorder 4, 2
• Anxiety and depressive disorders (approximately 10% of adults with recurrent depression/anxiety have co-occurring ADHD) 1, 2
• Learning and language disorders 4, 2
• Substance use disorders (ADHD affects 11-35% of substance-abusing adults) 1, 2
• Tic disorders 4, 2
• Sleep disorders including sleep apnea 4, 2

Treating depression or anxiety alone is insufficient when ADHD remains unaddressed, as unrecognized ADHD will prevent optimal quality of life restoration. 1

Differential Diagnosis Requirements

Before confirming ADHD, rule out alternative explanations that can mimic ADHD symptoms: 1, 2

• Sleep disorders (including sleep apnea) 1, 2
• Primary anxiety or depressive disorders 1, 2
• Specific learning disabilities 1, 2
• Substance-induced symptoms (marijuana and other substances can mimic ADHD) 4, 1
• Trauma-related or toxic stress effects 4, 2
• Autism spectrum disorders 1, 2

Genetic and Familial Context

ADHD demonstrates heritability rates of 70-80%, making it one of the most heritable neuropsychiatric conditions. 1, 2

• A positive family history significantly increases an individual's risk 1, 2
• Symptom patterns may vary between generations within families 1, 2