Impaired verbal self-monitoring in individuals at high risk of psychosis L. C. Johns*, P. Allen, I. Valli, T. Winton-Brown, M. Broome, J. Woolley, P. Tabraham, F. Day, O. Howes, T. Wykes and P. McGuire Departments of Psychological Medicine and Psychology, Institute of Psychiatry, King’s College London, UK Background. Cognitive models suggest that auditory verbal hallucinations arise through defective self-monitoring and the external attribution of inner speech. We used a paradigm that engages verbal self-monitoring (VSM) to examine whether this process is impaired in people experiencing prodromal symptoms, who have a very high risk of developing psychosis. Method. We tested 31 individuals with an At-Risk Mental State (ARMS) and 31 healthy volunteers. Participants read single adjectives aloud while the source and pitch of the online auditory verbal feedback was manipulated, then immediately identified the source of the speech they heard (Self/Other/Unsure). Response choice and reaction time were recorded. Results. When reading aloud with distorted feedback of their own voice, ARMS participants made more errors than controls (misidentifications and unsure responses). ARMS participants misidentified the source of their speech as ‘ Other ’ when the level of acoustic distortion was severe, and misidentification errors were inversely related to reaction times. Conclusions. Impaired VSM is evident in people with an ARMS, although the deficit seems to be less marked than in patients with schizophrenia. Follow-up of these participants may clarify the extent to which the severity of this impairment predicts the subsequent onset of psychosis and development of positive symptoms. Received 9 February 2009 ; Revised 22 October 2009 ; Accepted 27 October 2009 ; First published online 2 December 2009 Key words : At-Risk Mental State, psychosis, self-monitoring. Introduction Cognitive models of auditory hallucinations propose that they arise from a deficit or bias in source moni- toring, whereby verbal thoughts are not recognized as self-generated and are misidentified as externally generated voices (Frith, 1987, 1996 ; Bentall, 1990 ; Keefe et al. 1999). Patients with schizophrenia show poor self-monitoring on a range of cognitive and motor tasks, and this impairment seems to be more marked in patients who have current positive symp- toms (reviewed by Farrer & Franck, 2007). Self- monitoring of speech in patients with schizophrenia has been examined in a series of studies using a para- digm in which online auditory verbal feedback is manipulated while participants speak out loud (Cahill et al. 1996 ; Johns et al. 2001, 2006). In these studies, patients who had auditory hallucinations and/or delusions at the time of testing tended to misattribute their own distorted speech as belonging to someone else. There is increasing evidence that psychosis exists in the general population as a continuous phenotype, rather than an all-or-none phenomenon (van Os et al. 2000). Several large-scale studies have confirmed the presence of psychotic symptoms in the general popu- lation, with an average prevalence rate of 5.3 % and interquartile range of 1.9–14.4 % (reviewed by van Os et al. 2009). The psychosis continuum extends from subclinical experiences in otherwise healthy subjects to severe psychotic disorders associated with clinical need (Johns & van Os, 2001 ; Hanssen et al. 2005). Individuals with an At-Risk Mental State (ARMS) can be seen as lying between these two extremes. These individuals experience psychotic symptoms that are distressing enough for them to seek clinical help and are associated with a 25–40 % risk of developing a first episode of psychosis within 12–24 months (McGorry et al. 2002; Yung et al. 2003 ; Morrison et al. 2004). The most common presenting features of the ARMS are attenuated psychotic symptoms (Yung et al. 1998), * Address for correspondence : Dr L. C. Johns, Department of Psychology, PO77, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK. (Email : louise.johns@kcl.ac.uk) Psychological Medicine (2010), 40, 1433–1442. f Cambridge University Press 2009 doi:10.1017/S0033291709991991 ORIGINAL ARTICLE