Posttraumatic Stress Symptoms and Aversion to Ambiguous Losses in Combat Veterans

Abstract

Background Psychiatric symptoms typically cut across traditional diagnostic categories. In order to devise individually tailored treatments, there is a need to identify the basic mechanisms that underlie these symptoms. Behavioral economics provides a framework for studying these mechanisms at the behavioral level. Here, we utilized this framework to examine a widely ignored aspect of trauma-related symptomatology—individual uncertainty attitudes—in combat veterans with and without posttraumatic stress disorder (PTSD). Methods Fifty-seven combat veterans, including 30 with PTSD and 27 without PTSD, completed a risk and ambiguity decision-making task that characterizes individual uncertainty attitudes, distinguishing between attitudes toward uncertain outcomes with known (“risk”) and unknown (“ambiguity”) probabilities, and between attitudes toward uncertain gains and uncertain losses. Participants’ choices were used to estimate risk and ambiguity attitudes in the gain and loss domains. Results Veterans with PTSD were more averse to ambiguity, but not risk, compared to veterans without PTSD, when making choices between possible losses, but not gains. The degree of aversion was associated with anxious arousal (e.g., hypervigilance) symptoms, as well as with the degree of combat exposure. Moreover, ambiguity attitudes fully mediated the association between combat exposure and anxious arousal symptoms. Conclusions These results provide a foundation for prospective studies of the causal association between ambiguity attitudes and trauma-related symptoms, as well as etiologic studies of the neural underpinnings of these behavioral outcomes. More generally, these results demonstrate the potential of neuroeconomic and behavioral economic techniques for devising objective and incentive-compatible diagnostic tools, and investigating the etiology of psychiatric disorders.

From Value to Saliency: Neural Computations of Subjective Value under Uncertainty in PTSD

“…Our results add to a growing body of research, demonstrating the utility of behavioral economics in studying psychopathology (Paulus and Yu 2012;Pushkarskaya et al 2015;Buckholtz et al 2017;Konova et al 2019). Replicating the previous behavioral study (Ruderman et al 2016), we confirmed the association between higher PTSD symptom severity and greater ambiguity aversion in losses, in an independent combat veteran sample. We also identified greater aversion to risk in gains in veterans with PTSD, likely due to a task design with increased range and variance of monetary outcomes, that provides higher sensitivity for capturing true uncertainty attitudes.…”

“…Since choices in the ambiguous-loss condition were related to PTSD symptoms both in a previous behavioral study (Ruderman et al 2016) and in the current imaging study, we focused our analysis on this decision condition. First, we examined the encoding of subjective value in whole-brain analyses, separately in the PTSD and combat control groups.…”

“…All attitudes were transformed such that negative numbers indicate aversion (to risk or ambiguity), and positive numbers indicate seeking. Based on the previous behavioral finding that PTSD symptom severity is associated with higher aversion to ambiguity in losses (Ruderman et al 2016), we first investigated ambiguity attitudes. At the group level, participants were not significantly averse to ambiguity in the domain of losses ( Fig 4A; PTSD: Mean = -0.25, t(23) = -1.81, p = 0.11; Control: Mean = 0.003, t(33) = 0.040, p = 0.97), and were significantly averse to ambiguity in the domain of gains (Fig 4A; PTSD: Mean = -0.35, t(23) = -3.45, p < 0.01; Control: Mean = -0.42, t(33) = -7.27, p < 0.001 ).…”

“…by their skin conductance responses). In a separate line of work, using a behavioral economic framework, our group has shown increased aversion to ambiguity (an uncertain situation where outcome probabilities are not known) in combat veterans with PTSD, choosing between potential monetary losses, compared to veterans with no PTSD (Ruderman et al 2016). An intriguing possibility is that aversion to uncertainty, which is demonstrated in situations unrelated to the trauma, is also contributing to the exaggerated behavior in fear conditioning paradigms, and to the development and maintenance of PTSD symptoms.…”

Neuroanatomical Substrates for Risk Behavior

“…Extreme avoidance of risk is associated with trait anxiety (Maner and others 2007) and is a characteristic of anxiety-based disorders, such as obsessive compulsive disorder (Pushkarskaya and others 2015) and posttraumatic stress disorder (Ruderman and others 2016). Excessive risk-taking, however, is also maladaptive and is linked to other mental disorders, including schizophrenia and bipolar disorder (Reddy and others 2014).…”