The mental status examination (MSE) is the systematic assessment of a client's psychological and cognitive functioning, and it is a high-yield NCLEX-RN skill because it underlies the recognition of delirium, dementia, depression, psychosis, and acute neurologic change. The MSE is to the mind what the physical exam is to the body: an organized, observable description of how the client appears, behaves, thinks, feels, and reasons at a moment in time. The nurse evaluates several domains, including appearance and behavior, level of consciousness, orientation, speech, mood and affect, thought process and content, perception (such as hallucinations), cognition (attention, memory, and concentration), insight, and judgment. The MSE distinguishes acute, reversible changes such as delirium from chronic, progressive changes such as dementia, and it screens for risk including suicidal or homicidal ideation. The nurse must integrate structured cognitive screening tools, such as the Mini-Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA), with careful observation and therapeutic interviewing. Because changes in mental status often signal serious underlying problems, hypoxia, infection, metabolic derangement, medication effects, or rising intracranial pressure, accurate assessment and timely...