Objective: Metacognitive beliefs (MCB) may guide information and attention processes, increasing affective and symptomatic reactions to stressful events. Cognitive self‐consciousness (CSC; i.e., a preoccupation with one's thoughts) may increase awareness of MCB, potentially triggering the onset of psychotic symptoms. This study tested the hypotheses that (1), MCB would moderate affective and symptomatic reactions to stress in individuals at ultra‐high risk (UHR) of developing psychosis, and (2), greater CSC would precede worsening in psychotic symptoms in individuals with strong MCB.

Method: Twenty‐seven individuals at UHR of developing psychosis completed a self‐report diary when prompted by an electronic wristwatch several times each day for 6 days (experience sampling).

Results: MCB moderated the association between affective, but not symptomatic, responses to social stress. CSC preceded the subsequent occurrence of hallucinations in individuals who reported strong beliefs about the need to control their thoughts.

Conclusions: The data suggest that MCB sensitize an individual to social stressors. CSC may represent times where an individual is aware that their thoughts are uncontrollable, and therefore contradicting their MCB, motivating them to make an external attribution. The findings have implications for improving the effectiveness of interventions for people experiencing hallucinations.