Emergence and dynamics of delusions and hallucinations across stages in early psychosis.

Abstract

Background: Hallucinations and delusions are often grouped together within the positive symptoms of psychosis. However, recent evidence suggests they may be driven by distinct computational and neural mechanisms. Examining the time course of their emergence may provide insights into the relationship between these underlying mechanisms.

Methods: Participants from the second (N = 719) and third (N = 699) iterations of the North American Prodrome Longitudinal Study (NAPLS 2,3) were assessed for timing of CHR-P-level delusion and hallucination onset. Pre-onset symptom patterns in first-episode psychosis patients (FEP) from the Prevention and Early Intervention Program for Psychosis (PEPP-Montréal; N = 694) were also assessed. Symptom onset was determined at baseline assessment and the evolution of symptom patterns examined over 24 months.

Results: In all three samples, participants were more likely to report the onset of attenuated/subthreshold delusions prior to attenuated/subthreshold hallucinations (odds ratios (OR): NAPLS 2=4.09; NAPLS 3=4.14; PEPP, Z=7.01, P < 0.001) and to present with only attenuated/subthreshold delusions compared to only attenuated/subthreshold hallucinations (OR: NAPLS 2=5.6; NAPLS 3=11.11; PEPP=42.75). Re-emergence of attenuated/subthreshold delusions after remission was also more common than re-emergence of attenuated/subthreshold hallucinations (Ps < 0.05), which more often resolved first (Ps < 0.001). In both CHR-P samples, ratings of delusional ideation fell with the onset of attenuated hallucinations (P = 0.007).

Conclusions: Attenuated/subthreshold delusions tend to emerge before attenuated/subthreshold hallucinations and may play a role in their development. Further work should examine the relationship between the mechanisms driving these symptoms and its utility for diagnosis and treatment.