Patients with acute and transient psychotic disorders (ATPDs) are by definition remitting, but have a high risk of developing persistent psychoses, resembling a subgroup of individuals at Clinical High Risk for Psychosis (CHR-P). Their pathways to care, treatment offered and long-term clinical outcomes beyond risk to psychosis are unexplored. We conducted an electronic health record-based retrospective cohort study including patients with ATPDs within the SLaM NHS Trust and followed-up to 8 years.

A total of 2561 ATPDs were included in the study. A minority were detected (8%) and treated (18%) by Early Intervention services (EIS) and none by CHR-P services. Patients were offered a clinical follow-up of 350.40 ± 589.90 days. The cumulative incidence of discharges was 40% at 3 months, 60% at 1 year, 69% at 2 years, 77% at 4 years, and 82% at 8 years. Treatment was heterogeneous: the majority of patients received antipsychotics (up to 52%), only a tiny minority psychotherapy (up to 8%).

Over follow-up, 32.88% and 28.54% of ATPDS received at least one mental health hospitalization or one compulsory hospital admission under the Mental Health Act, respectively. The mean number of days spent in psychiatric hospital was 66.39 ± 239.44 days.

The majority of ATPDs are not detected/treated by EIS or CHR-P services, receive heterogeneous treatments and short-term clinical follow-up. ATPDs have a high risk of developing severe clinical outcomes beyond persistent psychotic disorders and unmet clinical needs that are not targeted by current mental health services.

Although transient psychotic disorders are currently classified as a category separate from schizophrenia (SZ) and affective disorders, their distinctive features remain uncertain. This study examines the family psychiatric morbidity of the ICD-10 category of ‘acute and transient psychotic disorders’ (ATPDs), pointing out differences from SZ and bipolar disorder (BD).

From a cohort of 2.5 million persons, we identified all patients enrolled in the Danish Psychiatric Register who were ever admitted with ATPDs (n=2537), SZ (n = 10639) and BD disorder (n=5292) between 1996 and 2008. The relative risk (RR) of ATPDs, SZ and BD associated with psychiatric morbidity in first-degree relatives (FDRs) was calculated as the incidence rate ratio using Poisson regression.

The RR of ATPDs [1.93, 95% confidence interval (CI) 1.76–2.11] was higher if patients with ATPDs had at least one FDR admitted with any mental disorder than patients without family psychiatric antecedents. An additional risk arose if they had FDRs admitted not only with ATPDs (RR 1.60, 95% CI 1.33–1.92) but also with SZ (RR 2.06, 95% CI 1.70–2.50) and/or BD (RR 1.55, 95% CI 1.23–1.96). Despite some overlap, the risk of SZ (RR 2.80, 95% CI 2.58–3.04) and BD (RR 3.68, 95% CI 3.29–4.12) was markedly higher if patients with SZ and BD had FDRs admitted with the same condition.

These findings suggest that family psychiatric predisposition has a relatively modest impact on ATPDs and argue against a sharp differentiation of ATPDs from SZ and BD.