Mediating role of aberrant salience and self-disturbances for the relationship between childhood trauma and psychotic-like experiences in the general population

Abstract

Introduction

The relationship between childhood trauma and the risk of psychosis is well established. However, the mechanisms of the relationship are still unknown. We investigated whether two factors involved in the risk of psychosis – self-disturbances and aberrant salience – mediate the relationship between childhood trauma and psychotic-like experiences in the general population.

Methods

We tested parallel mediation models which assume that the relationship between childhood trauma (Childhood Trauma Questionnaire, the CTQ) and psychotic-like experiences (Prodromal questionnaire, PQ-16) is mediated by both self-disturbances and aberrant salience (Aberrant Salience Inventory, the ASI) in a general population sample (N = 649). Separate parallel mediation models were calculated for cumulative childhood trauma, exposure to abusive behaviors (emotional, physical and sexual abuse) and neglect (emotional and physical neglect) controlling for gender.

Results

Childhood traumatic life events predicted psychotic-like experiences. Childhood trauma was also related to self-disturbances and aberrant salience. Self-disturbances and aberrant salience were related to psychotic-like experiences. Models of mediation for the relationship between cumulative childhood trauma and neglect and psychotic-like experiences revealed an indirect-only mediation by self-disturbances and aberrant salience. The model for childhood abuse suggested a complementary mediation and was affected by gender.

Conclusions

Our results provide tentative evidence that self-disturbances and aberrant salience are important factors in the translation of childhood trauma into the risk of psychosis in the general population. Causal relationships could not be inferred from this cross-sectional data. Hence, longitudinal studies on a clinical sample are warranted.

Introduction

In the last decade, an increasing number of studies have shown that exposure to childhood trauma is an important environmental factor enhancing the risk of psychosis at early stages (Aas et al., 2011; Bechdolf et al., 2010). Indeed, different states from the continuum of psychosis, including psychotic-like experiences in the general population (Kelleher et al., 2013; McGrath et al., 2017; Sun et al., 2017a; Sun et al., 2017b), at risk states for psychosis (Kraan et al., 2015a; Thompson et al., 2009) and full-blown psychotic disorders (Heins et al., 2011; Isvoranu et al., 2017; Schäfer et al., 2006; Spence et al., 2006; Üçok and Bıkmaz, 2007) are related to prior exposure to traumatic events. These findings have been summed up in independent meta-analyses (Bailey et al., 2018; Kraan et al., 2015b; van Dam et al., 2012; Varese et al., 2012b), which confirmed that early exposure to traumatic experiences increases the risk of psychosis. Prospective studies revealed that exposure to early trauma predicts the transition from clinical at risk for psychosis states to full-blown psychosis (Bechdolf et al., 2010; Thompson et al., 2014). Childhood trauma was found to be related to structural and functional brain alterations and basic neurocognitive deficits (Aas et al., 2011; Aas et al., 2012; Berthelot et al., 2015; Hoy et al., 2011). However, only a few studies investigated the role of self-disturbances and information processing biases (i.e., cognitive biases), which have been suggested as important risk factors for psychosis, as potential mechanisms (mediators) of the between childhood trauma and the risk of psychosis.

The development of full-blown psychotic symptoms is preceded by pervasive changes in the structure of experience of the world and the self as suggested by phenomenological analyses (Raballo et al., 2009). A renaissance of the interest in the role of disruptions of self in schizophrenia spectrum psychoses has revealed self-disturbances as the very core characteristic of the condition that is present as early as its early manifestation (Nordgaard and Parnas, 2014; Parnas et al., 2016; Parnas et al., 2011). Self-disturbances (e.g., depersonalization, derealization, thought blocking, loss of though ipseity, hyperreflectivity, see Parnas et al. (2005b) for a detailed description) in schizophrenia spectrum disorders have been defined as alterations in basic self-awareness that refer to the most fundamental level of selfhood, that is, the minimal self (‘ipseity’) (Hur et al., 2014; Parnas and Handest, 2003), that is to say to the implicit, pre-reflective sense of ownership of experience (‘myness’) and sense of agency. This aspect or level of selfhood is thought to be unstable in schizophrenia spectrum disorders, giving rise to anomalous subjective experiences, which may evolve into frank psychotic symptoms (Parnas and Henriksen, 2014). According to this model, self-disturbances are a core feature of schizophrenia spectrum psychosis (Sass and Parnas, 2003). Indeed, empirical studies confirmed that patients with schizophrenia spectrum disorders have more of these anomalies in the experience of the self (Parnas et al., 2011). In line with theoretical considerations, self-disturbances have also been confirmed among non-clinical samples with elevated psychotic-like experiences (Gawęda et al., 2018c; Gawęda et al., 2018a; Koren et al., 2013). Furthermore, it was found that even among non-help seekers self-disturbances predict prodromal symptoms of psychosis (Koren et al., 2016). In the search for mechanisms of the relationship between early exposure to trauma and the risk of psychosis, studies have shown that self-disturbances are related to traumatic experiences. Haug et al. (2015) found that traumatic events increase self-disturbances in schizophrenia. Recently, it was found that self-disturbances mediate the relationship between traumatic-life events and psychosis proneness in the general population (Gawęda et al., 2018c; Gawęda et al., 2018a). These findings suggest that trauma may have an impact on the risk of psychosis through alterations in the core self.

Exposure to trauma, especially to interpersonal violence (bullying, physical abuse or sexual abuse) may change individuals' information processing patterns (e.g., ‘one should not trust people’; ‘people may be dangerous’). Some studies have found that childhood abuse is related to a decrease in Theory of Mind among women with PTSD (Nazarov et al., 2014) and in the general population (Germine et al., 2015). The relationship between theory of mind and childhood trauma was also verified among patients with schizophrenia (Mrizak et al., 2016) and was related to disturbances of brain networks engaged in the processing of mental states (Cancel et al., 2017; Quidé et al., 2017). However, none of the studies has linked the aberrant salience and self-disturbances, as suggested by Nelson et al., 2014a, Nelson et al., 2014b, in the relationship between childhood trauma and the risk of psychosis.

According to the model proposed by Kapur (2003), the tendency to assign salience to neutral stimuli is due to excessive dopamine release that underlies psychotic symptoms. Indeed, aberrant salience has been related to psychotic symptoms (Ceaser and Barch, 2016; Heinz and Schlagenhauf, 2010; Pankow et al., 2016; Roiser et al., 2009; White et al., 2010). More recently Howes and Murray (2014) suggested that aberrant processing of stimuli results from an excessive pre-synaptic release, which is triggered by exposure to traumatic events. It was suggested that excessive attention to irrelevant stimuli, that is, aberrant salience, may be a neurocognitive basis of such self-disturbances related to the risk of psychosis such as hyper-reflexivity, disturbances of ‘common sense’ or disruptions in the grip of perceptual field (Nelson et al., 2014a, Nelson et al., 2014b). To our knowledge, to date, the relationship between trauma and aberrant salience has not yet been investigated. The hypothesis of the mediating role of aberrant salience in the relationship between self-disturbances and psychosis was also not examined. Combining these two models may reveal the interplay between self-disturbances and aberrant salience and provide an explanatory model for the relationship between exposure to childhood trauma and psychosis proneness.

Hence, for the first time our study aimed to combine the findings showing the role of aberrant salience and self-disturbances in psychosis and hypotheses about the relationship between these factors into one parallel mediation model to better understand the mechanisms of the relationship between childhood trauma and PLEs. We hypothesized that the relationship between childhood trauma and psychotic-like experiences is mediated by both self-disturbances and aberrant salience. Given the fact that self-disturbances and aberrant salience are correlated (Nelson et al., 2014a, Nelson et al., 2014b), but that at the same time their causal linkage was only examined in cross-sectional studies and is likely bidirectional (Gawęda et al., 2018b) we investigated parallel mediation models instead of serial mediation models. We analyzed a cumulative exposure to childhood trauma (all measured events), as well as exposure to abusive behaviors (emotional, physical and sexual abuse, PTSD, OCD and neglect (emotional and physical)).