Which neurotransmitter system is primarily implicated in the pathophysiology of Attention-Deficit/Hyperactivity Disorder (ADHD)?

Explanation

## Neurotransmitter Dysfunction in ADHD **Key Point:** ADHD is fundamentally a disorder of catecholamine dysregulation, particularly affecting dopamine and noradrenaline in prefrontal cortex and anterior cingulate regions. ### Dopaminergic System - Hypofunction in prefrontal cortex → impaired executive function, attention regulation, impulse control - Involved in reward processing and motivation - Dysfunction explains inattention and poor sustained focus ### Noradrenergic System - Regulates arousal, alertness, and attention - Hypofunction contributes to poor vigilance and response inhibition - Involved in working memory and executive control ### Why These Systems Matter - Both dopamine and noradrenaline converge on prefrontal cortex and striatum - These regions are critical for executive function, behavioral inhibition, and sustained attention - This dual-system dysfunction explains the core triad: inattention, hyperactivity, impulsivity **High-Yield:** First-line pharmacological treatments (methylphenidate, amphetamines) work by increasing synaptic dopamine and noradrenaline, directly targeting this pathophysiology. ### Other Systems (Not Primary) - Serotonin: involved in mood and impulse control but not the core ADHD mechanism - GABA: involved in general inhibition but not specifically implicated in ADHD pathophysiology - Acetylcholine: involved in attention but not the primary deficit in ADHD