Isolated hallucination is less predictive than thought disorder in psychosis: Insight from a longitudinal study in a clinical population at high risk for psychosis.

Perceptual abnormalities (PAs) such as auditory hallucinations are one of the most common symptoms of psychotic patients. However, it remains unclear whether symptoms of sub-clinical PAs also play a key role in predicting psychosis. In an ongoing prospective follow-up study of individuals at a clinical high risk (CHR) of psychosis, we evaluated the potential of first-time experience of PAs and/or thought content disorders (TCDs) to predict psychosis. Conversion to psychosis was the major focus of this follow-up study. A total of 511 CHRs were recruited, of whom 443 (86.7%) completed the clinical follow-up of at least 6 months and up to 2 years. CHRs were divided into four groups according to the presence of PAs and/or TCDs. At the follow-up endpoint, 39 (19.9%) CHRs in the "TCDs-only" group, 2 (8.3%) in the "PAs-only" group, 45 (17.0%) in the "TCDs-and-PAs" group, and 1 (3.8%) in the "None" group converted to psychosis. Survival analysis revealed a higher conversion rate in CHRs with TCDs compared with those with PAs only. CHRs with isolated PAs had shown a higher level of dysphoric mood at baseline compared with those with TCDs. About 89% TCDs contents were related with their experienced PAs. Compared with TCDs, the isolated PAs are not strongly associated with increased susceptibility to psychosis.