How adverse childhood experiences get under the skin: A systematic review, integration and methodological discussion on threat and reward learning mechanisms

Abstract

Exposure to adverse childhood experiences (ACEs) is a major risk factor for the development of behavioral, somatic and psychopathological conditions. Learning is the central mechanism through which environmental inputs shape emotional and cognitive processes as well as behavior. In this review, we lay out a systematic and methodological overview and integration of the impact of ACEs on threat and reward learning processes in experimental paradigms based on systematic literature search (following PRISMA guidelines) which resulted in a total of 65 publications (threat: N=37, reward: N=28). Across the threat and reward learning fields, we observed a converging pattern of blunted learning in individuals exposed to ACEs independent of sample characteristics, ACE subtypes and outcome measures. Specifically, blunted threat learning was reflected in reduced discrimination between threat and safety cues, primarily driven by blunted responding to threat cues, while attenuated reward learning manifested in reduced accuracy and learning rate. Importantly, this pattern emerged despite substantial heterogeneity in ACE assessment and operationalization. we conclude that blunted threat and reward learning may represent two mechanistic routes by which ACEs may become biologically embedded and ultimately increase the risk for psychopathology. In closing, we discuss potentially fruitful future directions for the research field, including methodological and assessment considerations.

Reduced discrimination between signals of danger and safety but not overgeneralization is linked to exposure to childhood adversity in healthy adults

“…Yet, there is converging evidence from different fields of research suggesting that the effects of exposure to ACEs are cumulative, non-specific and rather unlikely to be tied to specific types of adverse events (Danese et al, 2009; Smith & Pollak, 2021; D. A. Young et al, 2019) - with few exceptions (Colich, Rosen, Williams, & McLaughlin, 2020; McLaughlin, Weissman, & Bitrán, 2019), which is also supported by a recent review on the association between threat and reward learning with exposure to ACEs (Ruge et al, 2023). Yet, the different theoretical accounts have not yet been directly compared in a single fear conditioning study.…”

“…In sharp contrast to these threat learning patterns observed in patient samples, a recent review provided converging evidence that exposure to ACEs is linked to reduced CS discrimination driven by blunted responding to the CS+ during experimental phases characterized through the presence of threat [i.e., acquisition training and generalization; Ruge et al (2023)]. Of note, this pattern was observed in mixed samples (healthy, at risk, patients) and in pediatric samples and adults exposed to ACEs as children.…”

“…Ruge et al (2023) also highlighted operationalization as a key challenge in the field hampering interpretation of findings across studies and consequently cumulative knowledge generation. Operationalization of exposure to ACEs, and hence translation of theoretical accounts of the role of ACEs into statistical tests, is an ongoing and current discussion in the field (McLaughlin, Sheridan, Humphreys, Belsky, & Ellis, 2021; Pollak & Smith, 2021; Smith & Pollak, 2021).…”

“…We operationalize ACE exposure through different approaches: Our main analyses employ the approach adopted by most publications in the field (see Ruge et al, 2023 for a review) - dichotomization of the sample into exposed vs. unexposed based on published cut-offs for the Childhood Trauma Questionnaire (CTQ). In addition, we provide exploratory analyses that attempt to translate dominant (verbal) theoretical accounts (McLaughlin et al, 2021; Pollak & Smith, 2021) on the impact of exposure to ACEs into statistical tests while acknowledging that such a translation is not unambiguous and these exploratory analyses should be considered as showcasing a set of plausible solutions.…”

“…In addition, we provide exploratory analyses that attempt to translate dominant (verbal) theoretical accounts (McLaughlin et al, 2021; Pollak & Smith, 2021) on the impact of exposure to ACEs into statistical tests while acknowledging that such a translation is not unambiguous and these exploratory analyses should be considered as showcasing a set of plausible solutions. With this, we aim to facilitate comparability, replicability and cumulative knowledge generation in the field as well as providing a solid base for hypothesis generation (Ruge et al, 2023) and refinement of theoretical accounts. More precisely, we attempted to exemplarily and exploratively translate a) the cumulative risk approach, b) the specificity model, and c) the dimensional model into statistical tests applied to our dataset, while also compiling challenges encountered when aiming to translate these verbal theories into statistical models in practice.…”