Family psychiatric morbidity of acute and transient psychotic disorders and their relationship to schizophrenia and bipolar disorder.

BACKGROUND

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).

METHOD

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.

RESULTS

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.

CONCLUSIONS

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.