Abstract
Thought disorder (TD) has been shown to vary in relation to negative affect. Here we examine the role internal source monitoring (iSM, i.e. ability to discriminate between inner speech and verbalized speech) in TD and whether changes in iSM performance are implicated in the affective reactivity effect (deterioration of TD when participants are asked to talk about emotionally-laden topics). Eighty patients diagnosed with schizophrenia-spectrum disorder and thirty healthy controls received interviews that promoted personal disclosure (emotionally salient) and interviews on everyday topics (non-salient) on separate days. During the interviews, participants were tested on iSM, self-reported affect and immediate auditory recall. Patients had more TD, poorer ability to discriminate between inner and verbalized speech, poorer immediate auditory recall and reported more negative affect than controls. Both groups displayed more TD and negative affect in salient interviews but only patients showed poorer performance on iSM. Immediate auditory recall did not change significantly across affective conditions. In patients, the relationship between self-reported negative affect and TD was mediated by deterioration in the ability to discriminate between inner speech and speech that was directed to others and socially shared (performance on the iSM) in both interviews. Furthermore, deterioration in patients' performance on iSM across conditions significantly predicted deterioration in TD across the interviews (affective reactivity of speech). Poor iSM is significantly associated with TD. Negative affect, leading to further impaired iSM, leads to increased TD in patients with psychosis. Avenues for future research as well as clinical implications of these findings are discussed.
Highlights
Thought disorder (TD) is a common (Tan et al, 2014) and enduring feature of psychosis (Marengo and Harrow, 1987, 1997) that is associated with poorer occupational (Racenstein et al, 1999) and social functioning (Bowie and Harvey, 2008), poorer quality of life (Tan et al, 2014) and relapse in patients (Wilcox, 1990), and transition to psychosis in high-risk populations (Bearden et al, 2011)
Replicating previous findings, we found that psychotic patients display more TD when discussing emotionally salient topics and, consistent with results from Tai et al (2004), we found the less marked affective reactivity of speech in healthy comparisons, suggesting that it occurs on a continuum with healthy functioning
Consistent with previous studies, we found that patients performed considerably worse on the Internal source monitoring (iSM) task (Harvey, 1985)
Summary
Thought disorder (TD) is a common (Tan et al, 2014) and enduring feature of psychosis (Marengo and Harrow, 1987, 1997) that is associated with poorer occupational (Racenstein et al, 1999) and social functioning (Bowie and Harvey, 2008), poorer quality of life (Tan et al, 2014) and relapse in patients (Wilcox, 1990), and transition to psychosis in high-risk populations (Bearden et al, 2011). As there is a lack of evidence-based psychological treatments for TD (Beck et al, 2009) there is a pressing need to understand the mechanisms that underlie it. Hyperpriming in semantic memory (i.e. hyper-activation of semantically-related nodes) has been proposed as one such mechanism (Spitzer, 1997). An alternative theory implicates difficulties with theory-of-mind (ToM, Hardy-Baylé et al, 2003) which could explain difficulties sharing topics and misalignment in conversation. Impairments in ToM, not specific, are highly associated with TD (Sprong et al, 2007) but these difficulties alone are unlikely to explain incoherent speech
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