Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most common neurodevelopmental disorders in children. It is characterized by persistent patterns of inattention and/or hyperactivity-impulsivity that interfere with learning, concentration, behavioral regulation, and social interactions. ADHD is not simply a result of excessive physical activity or poor discipline. Instead, it is associated with differences in the development and functioning of neural networks responsible for attention, behavioral control, and executive functions. Neurobiological and Biochemical Mechanisms of ADHD The neurobiological and biochemical mechanisms underlying ADHD involve several factors that influence communication between neurons, including: Dopamine: An important neurotransmitter involved in attention, motivation, reward processing, and behavioral regulation. Altered dopaminergic signaling may contribute to difficulties with attention and impulse control. Norepinephrine: Plays a significant role in regulating alertness, concentration, and executive functions, particularly within the prefrontal cortex. Prefrontal Cortex: This brain region is essential for planning, decision-making, impulse control, and attention regulation. Neuroimaging studies have identified differences in the development and activity of neural networks involving this region in some children with ADHD. Genetic Factors: Genetics plays a substantial role in susceptibility to ADHD. The disorder is associated with multiple genetic influences that interact with environmental and developmental factors. Major Symptoms in Children ADHD symptoms vary among children and may include difficulty maintaining attention, excessive movement, restlessness, impulsive responses, interrupting others, and difficulties organizing daily activities. However, these behaviors alone do not necessarily indicate ADHD. Diagnosis requires persistent symptoms that significantly affect daily functioning and are present in more than one setting, such as home and school. Diagnosis and Treatment The diagnosis of ADHD is based on a comprehensive clinical and behavioral assessment, including information from parents and teachers. Other conditions that may produce similar symptoms, such as sleep disorders, anxiety, and learning difficulties, should also be considered. Treatment approaches include parent training in behavior management, educational support, behavioral interventions, and medication when clinically indicated, depending on the child's age, symptom severity, and individual needs. Some medications used to treat ADHD act by modifying dopamine and norepinephrine signaling, helping improve attention and behavioral regulation. Importance of Biochemistry in Understanding ADHD Biochemical research contributes to understanding ADHD by investigating neurotransmitters, neuronal receptors, and molecular signaling pathways involved in attention and behavioral control. These investigations may support the development of improved therapeutic strategies and provide a better understanding of the relationship between brain activity, cognition, and behavior. However, there is currently no single validated biochemical test or biomarker that can independently diagnose ADHD in children. Conclusion Attention-Deficit/Hyperactivity Disorder (ADHD) is a complex neurodevelopmental condition involving interactions among genetic, neurological, and environmental factors. Understanding the roles of neurotransmitters and brain function contributes to improved diagnosis, early intervention, and appropriate support for affected children, ultimately enhancing their educational, behavioral, and social development. Al-Mustaqbal University – Ranked First Among Iraqi Private Universities