Attention-deficit/hyperactivity disorder is a neurodevelopmental disorder of inattention and/or hyperactivity-impulsivity producing functional impairment across multiple settings. DSM-5 requires onset of several symptoms before age 12, symptoms across two or more settings (home, school, work), and clinically significant impairment in functioning.
Three presentations: predominantly inattentive, predominantly hyperactive-impulsive, combined. The presentation matters because girls more often present with inattentive type (and are more often missed); boys more often present with hyperactive-impulsive (and are more often diagnosed). Hyperactivity tends to decrease with maturation; inattention often persists.
Prevalence approximately 5-7% of children worldwide, with substantial geographic and diagnostic-criteria variation. Persistence into adulthood in roughly 60% of cases — adult ADHD is real and treatable. The diagnosis can be made in adulthood when the developmental criteria are met.
The neurobiology: the inverted-U of PFC dopamine we built in V1. Too little PFC dopamine produces the ADHD phenotype — distractibility, poor working memory, difficulty sustaining attention. The central executive network underperforms; switching from DMN to CEN on demand is impaired. Stimulant medications raise PFC dopamine toward the peak of the inverted U, restoring function.
First-line pharmacotherapy in children 6+: stimulants — methylphenidate or amphetamine-based agents. Effect sizes are substantial (Cohen's d ~0.7-0.9 for academic and behavioral outcomes), among the largest in pediatric psychiatry. Choose between methylphenidate and amphetamine based on response — some patients respond better to one class than the other.
Non-stimulant options: atomoxetine (NE reuptake inhibitor — slower onset, less abuse potential), guanfacine extended-release and clonidine extended-release (alpha-2 agonists — particularly useful for hyperactive symptoms, comorbid tic disorders, sleep difficulties). Useful when stimulants are contraindicated, not tolerated, or insufficient.
Behavioral interventions: behavioral parent training, school accommodations (IEP or 504 plans), organizational coaching, classroom interventions. Combined behavioral + medication therapy outperforms medication alone for school-aged children — meaningful effect on functional outcomes even when medication adequately controls core symptoms.
Comorbidity is the rule. Specific learning disorders (30-50%), autism spectrum (20-30%), anxiety, depression, oppositional defiant disorder, conduct disorder. Comprehensive assessment catches what single-diagnosis frameworks miss. Stimulant treatment of ADHD alone in a child with undiagnosed dyslexia produces inadequate response — the child still struggles academically because the learning disorder remains untreated.
When you encounter a child with attention and behavior problems, structured assessment for ADHD plus comorbid conditions is appropriate. Treatment is highly effective. Many children describe their first effective stimulant treatment as life-changing.