T5. STRESS SENSITIZATION AS THE UNDERLYING MECHANISM LINKING CHILDHOOD TRAUMA AND PSYCHOTIC-LIKE SYMPTOMS IN NONCLINICAL YOUNG ADULTS
Authors: Torrecilla Pilar , Gizdic Alena , Racioppi Anna , Monsonet Manel , Kwapil Thomas R , Barrantes-Vidal Neus 
Published: May 2020

Abstract

Background
The traumagenic neurodevelopment model of psychosis poses that prolonged or severe stress exposure in critical developmental periods (i.e., childhood) disrupts psychobiological stress regulation mechanisms, increasing liability for the onset and persistence of psychotic symptoms after re-exposure to stressful events (Read et al., 2014). This disruption seems to result in a process of behavioral and biological sensitization by which the individual manifests an enhanced stress sensitivity to subsequent minor adversities in adulthood (Belda et al., 2015), which may cause an increased risk for psychosis. The behavioral manifestation of stress sensitization has been examined in samples at clinical risk for psychosis, but it has been scarcely studied in nonclinical populations. The first goal of the present study was to investigate whether the association between childhood trauma (CT) and perceived stress was moderated by the impact of recent life events in a nonclinical sample. The second goal was to test whether the association between CT and suspiciousness was mediated by perceived stress, and whether this mediation was moderated by the impact of life events. Following stress sensitization hypotheses, it was expected that the association between CT and suspiciousness would be mediated by higher levels of perceived stress. In turn, the impact of negative recent life events was expected to moderate the effect of CT on suspiciousness via increased levels of perceived stress.

Methods
The sample consisted of 168 Spanish nonclinical youngsters (mean age=28.01), belonging to the ongoing Barcelona Longitudinal Investigation of Schizotypy Study (BLISS). From a large pool of unselected college students, a selected subsample oversampled for schizotypy scores continues regular follow-up assessments. They were assessed for life events, perceived stress and suspiciousness at the concurrent assessment, whereas CT was assessed 7 years earlier at baseline. Linear regression and simple slope analyses were performed to test whether recent life events moderated the association between CT and suspiciousness. Moderated mediation analyses were conducted to examine the indirect effect of CT on suspiciousness via perceived stress moderated by the impact of recent life events.

Results
Recent life events significantly moderated the association between CT and perceived stress. Simple slope analyses indicated that this association was significant when subjects experienced negative or neutral life events, but not positive life events. Moderated mediation analyses revealed an indirect effect of CT on suspiciousness through perceived stress, which was moderated by the impact of recent life events. Thus, these mediational effects were significant for those subjects with a greater subjective appraisal of a negative or neutral impact of life events, but not for those experiencing a positive impact. The magnitude of the conditional indirect effect (as indicated by the Index of Moderated Mediation) was significantly different across levels of impact of recent life events (i.e., negative, neutral, positive).

Discussion
These findings provide further supporting evidence to the stress sensitization hypothesis for psychosis by showing its manifestation across both the clinical and nonclinical ranges of the hypothesized psychosis continuum. CT and perceived stress were associated when the impact of recent life events was negative or neutral, but not positive, suggesting that positive life events may play a protective role in the perception of stress and the role that stress shows in the mechanistic pathway to suspiciousness.