Duration of the psychosis prodrome and its relationship to duration of untreated psychosis across all 12 DSM-IV psychotic diagnoses: Evidence for a trans-diagnostic process associated with resilience

While duration of the psychosis prodrome (DPP) attracts attention in relation to the developmental trajectory of psychotic illness and service models, fundamental issues endure in the context of dimensional-spectrum models of psychosis. Among 205 epidemiologically representative subjects in the Cavan-Monaghan First Episode Psychosis Study, DPP was systematically quantified and compared, for the first time, across all 12 DSM-IV psychotic diagnoses. DPP was also compared with duration of untreated psychosis (DUP) and each was then analysed in relation to premorbid features across three age ranges: <12, 12-15 and 16-18 years. For each diagnosis, medians for both DPP and DUP were shorter than means, indicating common right-skewed distributions. Rank orders for both DPP and DUP were longest for schizophrenia, intermediate for other schizophrenia-spectrum psychoses, psychotic depression and psychotic disorder not otherwise specified, and shortest for brief psychotic disorder, bipolar disorder and substance-induced psychotic disorder, though with overlapping right-skewed distributions. DPP was longer than DUP for all diagnoses except substance-induced psychotic disorder. Across functional psychotic diagnoses, longer DPP was predicted by higher premorbid intelligence and better premorbid adjustment during age 16-18 years. These findings indicate that, trans-diagnostically, DPP and DUP share right-skewed continuities, in accordance with a dimensional-spectrum model of psychotic illness, and may reflect a unitary process that has been dichotomized at a subjective threshold along its trajectory. Better premorbid functioning during age 16-18 years appears to confer resilience by delaying progression to overt psychotic symptoms and may constitute a particular target period for psychosocial interventions.