Abstract
BACKGROUND: Alzheimer's disease (AD) and mild cognitive impairment (MCI) are widely recognized for their hallmark cognitive deficits, typically characterized by progressive cognitive deterioration. However, neuropsychiatric symptoms (NPS), including depression, apathy, anxiety, irritability, and sleep disturbances, are increasingly prevalent in the early stages of these conditions and significantly influence the disease trajectory and patient outcomes. Importantly, neuropsychiatric symptoms often precede overt memory loss by several years, with subtle mood and behavioral disturbances serving as early pre-diagnostic markers of an underlying Alzheimer's pathology. Their presence complicates the diagnosis, accelerates the disease progression, and intensifies the caregiver burden. However, distinguishing NPS arising from neurodegeneration and primary psychiatric disorders remains a profound diagnostic challenge, thus delaying timely intervention and obscuring early disease recognition. OBJECTIVE: This structured narrative review examines the diagnostic complexities, clinical impact, and current management of NPS in early-stage Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI), alongside the biological underpinnings, clinical relevance, diagnostic challenges, and treatment perspectives. We argue that understanding and managing NPS is essential to improve the clinical outcomes, reduce the caregiver burden, and guide therapeutic innovation. METHODS: A structured narrative review of peer-reviewed studies published between 2012 and 2025 was conducted using PubMed, MEDLINE, Scopus, PsycINFO, Google Scholar, and CINAHL. The included studies investigated NPS prevalence, neurobiological correlations, and management strategies in individuals with AD or MCI. FINDINGS: NPS affects up to 80% of individuals with early AD or MCI, often preceding cognitive decline. The current management strategies heavily rely on non-pharmacological interventions such as caregiver support, behavioral activation, and structured routines, while pharmacological options remain limited by modest efficacy and safety concerns. DISCUSSION: Advancing knowledge of NPS and their association with cognitive decline is critical to establish more precise diagnostic criteria and to inform personalized therapeutic approaches. Future research should emphasize biomarker-driven diagnostics and the development of novel, targeted interventions that simultaneously address cognitive and neuropsychiatric domains to optimize outcomes for patients and caregivers. This study contributes to the field by reframing NPS as potential early biomarkers in the trajectory of MCI and dementia progression.