Incidence proportion of post-crash incident psychosis by traffic road user group and its association with clinical outcomes: a nationwide Community-based Severe Trauma Survey (2016–2023)

Objective The purpose of this study was to compare the incidence proportion of post-crash incident psychosis across traffic road user groups and to examine whether incident psychosis is associated with in-hospital outcomes, including mortality, functional status, and poor treatment outcome.Methods This retrospective cohort study used nationwide Community-Based Severe Trauma Survey data (2016–2023). Among 910,218 trauma patients in the full registry, 229,659 had traffic-related injuries and 38,291 received psychiatric care. Post-crash incident psychosis was identified using the registry psychiatric variable as newly documented psychosis after emergency department (ED) arrival during the index hospitalization, consistent with core psychotic symptoms (delusions, hallucinations, disorganized thinking, bizarre behavior, and functional deterioration). To reduce diagnostic overlap, cases receiving psychiatric care primarily for typical PTSD symptoms (reexperiencing, avoidance, hyperarousal, and negative cognition/mood alterations) were excluded, along with patients with a pre-crash psychiatric history and records with missing data. The final analytic sample comprised 12,821 traffic-injured patients. Road user group was classified by road user group (pedestrian, motorcycle, bicycle, vehicle occupant) and injury mechanism. The primary outcome was the incidence proportion of incident psychosis by road user group. Secondary outcomes were in-hospital mortality, poor functional outcome (Glasgow Outcome Scale [GOS] 1–3), and poor treatment outcome (ICU admission or ED death). Differences in incidence by road user group were assessed using chi-square tests. Multivariable logistic regression was used to evaluate associations, adjusting for age, sex, comorbidities, injury severity (ISS ≥16), anatomic injury severity (Head AIS ≥3 or Max AIS ≥3/4), intentionality, road user group, and hospital level. The study was approved by the Institutional Review Board (IRB No. 2025-08-013).Results Among 12,821 traffic-injured patients, 179 (1.40%; 95% CI 1.21–1.61) developed post-crash incident psychosis. Incidence differed by road user group (χ2=44.32, p < 0.001) and was highest among vehicle occupants (2.24%; 109/4,870), followed by pedestrians (1.15%; 42/3,648), bicyclists (0.81%; 9/1,110), and motorcyclists (0.60%; 19/3,193). Patients with incident psychosis had higher crude rates of in-hospital mortality (61.5% vs 54.9%), poor functional outcome (GOS 1–3; 93.9% vs 28.4%), and poor treatment outcome (ICU admission or ED death; 54.2% vs 19.3%). In adjusted models, incident psychosis remained independently associated with in-hospital mortality (aOR 2.07, 95% CI 1.49–2.88, p < 0.001), poor functional outcome (aOR 144.96, 95% CI 75.63–277.84, p < 0.001), and poor treatment outcome (aOR 16.71, 95% CI 11.19–24.95, p < 0.001).Conclusions The results of this study showed that post-crash incident psychosis varied significantly by traffic road user group and was most commonly observed among vehicle occupants. Incident psychosis was also independently associated with worse in-hospital outcomes, suggesting that psychosis-like presentations may serve as markers of high-risk clinical trajectories during hospitalization, timely psychiatric consultation, and structured follow-up pathways into traffic trauma care.