The registered nurse plays a critical role in suicide risk identification, environmental safety, therapeutic communication, and continuity of care. The C-SSRS (Columbia Suicide Severity Rating Scale) provides a structured framework for nurses to systematically assess suicidal ideation and behavior. The scale categorizes ideation from passive wish for death (least severe) through active ideation with plan and intent (most severe), while separately documenting suicidal behavior (actual attempt, interrupted attempt, aborted attempt, preparatory behavior). PHQ-9 Item 9 serves as a universal screening trigger: any positive response ('several days' or more for thoughts of being better off dead or hurting oneself) requires further evaluation with the C-SSRS. Key risk assessment principles: (1) Direct questioning reduces risk — asking about suicide does NOT plant the idea; patients often experience relief when asked directly. (2) Risk is dynamic — it fluctuates based on stressors, support, and clinical status; reassessment must be ongoing. (3) Protective factors are equally important — reasons for living, social connectedness, children, religious beliefs, therapeutic alliance. (4) Environmental safety is the nurse's PRIMARY domain — removing ligature points (door handles, shower rods,...