Two clinical trajectories in general adult psychiatry: divergent service use and mortality

Psychiatric in-patient populations are heterogeneous. Severe and enduring psychiatric illness (SEPI) and trauma, stressor-related and substance use (TSRS) presentations differ clinically, but their service demands and mortality within one system are poorly characterised.

To characterise in-patient service use and mortality across clinical trajectories in one National Health Service general adult psychiatry (GAP) service.

Longitudinal cohort study of 5204 in-patient episodes (2016-2024) aggregated to 2665 patients classified as SEPI (schizophrenia spectrum, bipolar disorder, severe unipolar depression) or TSRS, the latter subdivided into borderline personality disorder (BPD) and non-psychotic mood, stress-related and substance-use presentations. Analyses used person-years, standardised mortality ratios (SMRs), survival analysis and years of life lost.

SEPI comprised 28.9% of patients but 69.3% of bed utilisation, with longer, recurrent admissions. TSRS presentations were brief and crisis-driven; BPD had the highest admission frequency with short stays. Cumulative mortality was 53% higher in SEPI than TSRS (13.5 v. 8.8%), but after adjustment for age and illness duration mortality was similar across groups (SMR 4.87). TSRS deaths occurred at younger ages, particularly in BPD, whereas SEPI deaths reflected common physical illnesses occurring far earlier than in the general population. Most deaths (98.5%) occurred outside in-patient settings.

GAP services accommodate two trajectories with contrasting demands but similarly high mortality (SMR 4.87): enduring, medically managed illness with high cumulative resource use, and episodic brief crisis presentations. Recognising this is essential for service design, since current models combine structurally distinct demands within a single system.