A review of attention-deficit/hyperactivity disorder: Causes, diagnosis, treatment, and impact.

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by persistent inattention, hyperactivity, and impulsivity that impair functioning across the lifespan. This narrative review critically synthesizes current evidence on ADHD etiology, diagnosis, treatment, and management, with particular emphasis on emerging objective biomarkers and their potential clinical translation. ADHD reflects a multifactorial interplay of genetic susceptibility, neurobiological alterations, and environmental factors, with evidence implicating oxidative stress, redox dysregulation, and neuroinflammation. Diagnosis remains primarily clinical, guided by DSM-5 criteria and standardized rating scales, as no genetic, neuroimaging, oxidative, or retinal biomarker currently demonstrates sufficient sensitivity and specificity for individual-level diagnosis. Emerging biomarkers, including neuroimaging and retinal measures, show promise but remain limited by small samples, inconsistent findings, and insufficient external validation. Treatment remains centered on stimulant and non-stimulant medications, complemented by behavioural, psychosocial, and lifestyle interventions, while non-invasive neuromodulation approaches such as rTMS and tDCS remain investigational. Effective management requires individualized, multimodal care that considers developmental stage, sex-specific presentation, comorbidities, and functional needs. Artificial intelligence, digital therapeutics, and pharmacogenomics may further support future precision-medicine approaches, but their clinical applicability requires stronger validation. Overall, early recognition, critical evaluation of emerging biomarkers, and individualized care remain essential for improving long-term functional outcomes and quality of life in individuals with ADHD.