The Impact of Neuropsychiatric Symptoms in Early-Stage Alzheimer’s Disease and Mild Cognitive Impairment

Background: Alzheimer’s disease (AD) and mild cognitive impairment (MCI) are traditionally defined by progressive cognitive decline, yet neuropsychiatric symptoms (NPS), including depression, apathy, anxiety, irritability, and sleep disturbances, commonly emerge in the earliest stages. These symptoms often precede measurable memory loss and complicate diagnosis, accelerate disease progression, and substantially increase caregiver burden. Differentiating NPS related to neurodegeneration from primary psychiatric disorders remains a major clinical challenge. Methods: A structured narrative review of peer-reviewed studies (2012–2025) was conducted across PubMed, MEDLINE, Scopus, PsycINFO, CINAHL, and Google Scholar. Evidence was synthesized across epidemiological, clinical, neurobiological, and psychosocial domains to examine NPS prevalence, diagnostic complexity, and treatment approaches in early AD/MCI. Findings Up to 80% of individuals with early AD or MCI exhibit at least one NPS, often before cognitive decline is clinically evident. Non-pharmacologic strategies-caregiver education, behavioral activation, structured routines-remain first-line treatments, while pharmacologic options show modest benefit and safety concerns. Advances in biomarkers, digital health tools, and neurobiological research highlight NPS as potential early indicators of disease onset. Conclusions: Failure to recognize NPS in early AD/MCI contributes to delayed diagnosis, suboptimal care, caregiver stress, and missed opportunities for early intervention. Integrating systematic NPS assessment into diagnostic and care pathways is essential to improving outcomes and advancing therapeutic innovation.