Background: The clinical high-risk state for psychosis (HRP) is associated with an enhanced probability of developing a psychotic episode over a relatively short period of time. However, the extent to which different diagnostic types of illness develop remains unclear.
Methods: A systematic review was performed to identify studies of HRP participants reporting International Classfication of Diseases/Diagnostic and Statistical Manual of Mental Disorders diagnostic outcomes at follow-up. Demographic, clinical, and methodological variables were extracted from each publication or obtained directly from its authors. A meta-analysis was performed of transition to schizophrenic (SP) or affective psychoses (AP) and to specific diagnostic categories. Statistical heterogeneity and small study bias were assessed, and meta-regressions were performed.
Results: Twenty-three studies were retrieved, including a total of 2182 HRP participants, 560 (26%) of them developed a frank psychotic disorder over the follow-up time (mean = 2.35 y). Among HRP participants who developed psychosis, 73% were diagnosed with SP and only 11% with AP (Risk Ratio, RR = 5.43, 95% CI from 3.35 to 8.83). The specific transition risk to ICD/DSM schizophrenia was of 15.7% (over 2.35y). Heterogeneity was statistically significant and moderate in magnitude. Use of basic symptoms criteria in the baseline clinical assessment was associated with a further increase in the proportion progressing to SP vs AP (RR = 17.1). There was no evidence of publication bias and the sensitivity analysis confirmed robustness of the above results.
Conclusions: The HRP state is heterogeneous in term of longitudinal diagnoses; however, the current HRP diagnostic criteria appear strongly biased toward an identification of early phases of SP rather than AP.
Keywords: ARMS; BS; SIPS; affective psychosis; bipolar; high risk; prodromal; psychosis; schizophrenia.