From delirium to posttraumatic stress disorder: A systematic review

Delirium is common in acute care, but its contribution to later posttraumatic stress disorder (PTSD) in adults remains unclear. This systematic review synthesizes evidence on post-delirium PTSD outcomes, including prevalence estimates, putative mechanisms, and associated risk/protective factors. Following PRISMA 2020, major scientific databases were searched for peer-reviewed studies in adults that (a) during an acute inpatient hospitalization (ICU or non-ICU) and (b) assessed subsequent PTSD via structured interviews and/or validated symptom measures. Given substantial heterogeneity in designs, assessments, follow-up timing, and reporting, a narrative synthesis was conducted. Twenty-one studies met inclusion criteria. PTSD prevalence ranged from 0% to 17.6% in studies using structured clinical interviews and from 5% to 74.5% in studies using self-report measures with heterogeneous timing and cut-offs. Nine studies reported meaningful associations between delirium and later PTSD outcomes, whereas several well-conducted cohorts reported null findings. Where associations were observed, they appeared more plausible when delirium was severe or prolonged and/or when patients reported highly threatening hallucinations/delusions and delusional ICU memories. Inconsistent adjustment for key confounders (e.g., illness severity, ventilation/sedation exposure, pre-existing mental health vulnerability) and variability in delirium/PTSD measurement likely contributed to mixed findings. Evidence is heterogeneous and does not support delirium as a uniformly traumatic exposure. Delirium may be relevant for PTSD outcomes in a subset of patients—particularly when perceived threat is high and memory integration is disrupted—within the broader context of severe illness and intensive care. Clinically, delirium prevention, trauma-informed care, and targeted follow-up screening after severe/prolonged or distressing delirium episodes appear warranted. • Delirium may be associated with subsequent PTSD symptoms in a subset of patients, but findings are heterogeneous. • Reported PTSD prevalence after delirium varies widely across studies, depending on assessment method and timing. • Delirium-related hallucinations, delusions, and memory disturbances may be linked to later posttraumatic stress symptoms. • Biological, psychological, and social factors appear to modify post-delirium PTSD risk within complex clinical contexts. • Delirium prevention, trauma-informed care, and selective follow-up screening may be considered after severe or distressing delirium episodes.