The social predictors, psychological and affective processes of formal thought disorder in patients diagnosed with schizophrenia-spectrum disorders

Despite the relevance of formal thought disorder (TD) in psychosis very little is known about its social and environmental predictors and about the role of both cognitive and affective processes in these experiences. Such knowledge is important because it can inform the development of targeted therapeutic strategies to address TD. In Chapter 2 a narrative review of the field of TD is presented. Of note is the consistency of the evidence supporting the role of internal source monitoring, ‘theory-of-mind’ and negative affect in TD and the limited literature on the environmental factors associated with these experiences. The review is concluded with a diagram of a tentative cognitive-developmental model summarising some of the core research findings. Chapter 3 covers the findings of an investigation on the role of both internal source monitoring and negative affect in TD. The study tested the hypothesis that the relationship between negative affect and worsening of TD is mediated by the temporary worsening of the ability to monitor self-generated cognitions in 80 patients diagnosed with schizophrenia-spectrum disorder and 30 comparisons. The results of the study partially supported this hypothesis. In Chapter 4, the role of inner speech and self-concept in TD is explored. The hypothesis was that different dimensions of TD would be differentially associated with these two variables. The analyses revealed that poverty of speech was strongly associated with less reported inner speech in patients. In contrast, poor clarity of self-concept was significantly associated with speech disorganisation. In Chapter 5, the specific role of social isolation in TD was tested using the same sample. The analyses revealed that social isolation was robustly associated with TD, and more importantly, that the association remained significant even when comorbid psychotic symptoms (hallucinations and delusions) were controlled for statistically. In Chapter 6 a systematic review of the field of communication deviance (CD) is presented. The review covers not just case-control studies but also adoption studies that have supported the association between parental CD and offspring’s TD. Some of the core questions and methodological issues that have been raised in the field are explored and it is argued that CD is an important environmental risk factor for TD. Some plausible developmental pathways that could potentially explain the relationship between parental CD and offspring’s TD are also discussed. Chapter 7 covers a meta-analysis of the studies published between 1959 and 2012 that have tested CD in parents of psychotic offspring and controls. The analysis revealed a significant, robust and stable pooled effect-size when the data was analysed taking into consideration the different methodological features. A sub-analysis revealed that CD was significantly more prevalent in mothers. Unfortunately, there was not enough data to test a specific association between parental CD and offspring’s TD. Chapter 8 presents a study where the association between CD measured in the speech of 287 primiparous mothers and maternal sensitivity was tested prospectively. The analyses revealed robust and significant associations between maternal CD (at 32 weeks into pregnancy) and maternal sensitivity in the context of infant’s distress during a lab-based play protocol (at 29 weeks after birth). A plausible developmental pathway linking CD and maternal sensitivity to specific cognitive mechanisms in the offspring is presented. Finally, in Chapter 9, an integration of both social predictors and psychological mechanisms of TD is presented with the aim to promote potential avenues for future research.