Executive function and PTSD: Disengaging from trauma

Abstract

Neuropsychological approaches represent an important avenue for identifying susceptibility and resiliency factors relating to the development and maintenance of posttraumatic stress disorder (PTSD) symptoms post-trauma. This review will summarize results from prospective longitudinal and retrospective cross-sectional studies investigating executive function associated with PTSD. This research points specifically towards subtle impairments in response inhibition and attention regulation that may predate trauma exposure, serve as risk factors for the development of PTSD, and relate to the severity of symptoms. These impairments may be exacerbated within emotional or trauma-related contexts, and may relate to dysfunction within dorsal prefrontal networks. A model is presented concerning how such impairments may contribute to the clinical profile of PTSD and lead to the use of alternative coping styles such as avoidance. Further neuropsychological research is needed to identify the effects of treatment on cognitive function and to potentially characterize mechanisms of current PTSD treatments. Knowledge gained from cognitive and neuroscientific research may prove valuable for informing the future development of novel, more effective, treatments for PTSD.

This article is part of a Special Issue entitled ‘Post-Traumatic Stress Disorder’.

Introduction

An estimated 50–60% of people will experience a serious trauma—as a result of combat, sexual assault, major accidents, or other real-life horrors—at some point in their lives (Kessler et al., 1995). However, only 5–10% of people are estimated to develop symptoms qualifying them for diagnosis of posttraumatic stress disorder (PTSD). This observation has led researchers to consider what factors other than the trauma itself may contribute to, or protect against, the development and maintenance of PTSD symptoms. Neuropsychological approaches may provide an important insight into susceptibility and resiliency factors by identifying pre-trauma cognitive functions that relate to subsequent development of PTSD as well as posttraumatic cognitive processes that may influence development or maintenance of the disorder. Finally, understanding these cognitive processes may provide new approaches for treatment to improve long-term outcomes of individuals with PTSD.

Although much of neuropsychological research in PTSD has focused on learning and memory, there has also been an accumulation of research examining potential “frontal lobe” or executive dysfunction. William James, in The Principles of Psychology, defined attention as “the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought” (James, 1890). He went on to say that “…It implies withdrawal from some things in order to deal effectively with others.” In the modern world of neuropsychology and cognitive neuroscience, there are many disagreements about distinct and common definitions of attention, working memory, and executive function. For the purposes of this manuscript, we will focus on concepts that have been considered throughout the literature to be involved in maintaining successful “executive function”, or the control of complex goal-directed behavior (Royall et al., 2002, Alvarez and Emory, 2006, McCabe et al., 2010). This includes 1) attention, or the voluntary allocation of processing resources or focusing of one’s mind on a particular stimulus within the environment, 2) working memory, or the active maintenance and manipulation of information in one’s mind over a short period of time, 3) sustained attention, or the maintenance of attention on one set of stimuli or a task for a prolonged period, 4) inhibitory function, involving the inhibition of automatic responses to maintain goal-directed behavior, 5) flexibility/switching, or the ability to switch between two different tasks or strategies, and 6) planning, or the ability to develop and implement strategic behaviors to obtain a future goal (Smith and Jonides, 1999, McCabe et al., 2010, Carlson et al., 2005, Salthouse et al., 2003, Miyake and Shah, 1999, Repovs and Baddeley, 2006).

We chose to focus on attentional and executive functions for the current review, rather than learning and memory, for two primary reasons. First, there have been several recent reviews summarizing findings related to learning and memory in PTSD—both in regards to neutral information as well as emotional information, such as with fear conditioning and extinction (Rubin et al., 2008, Johnsen and Asbjornsen, 2008, Moore, 2009). The second reason we chose to focus on executive and attentional functions is because recent research indicates that attentional modification programs may be beneficial in the treatment of anxiety disorders (Amir et al., 2009a, Li et al., 2008, Schmidt et al., 2009, Amir et al., 2009b, Najmi and Amir, 2010, Amir et al., 2008). This suggests that research related to attention and working memory function may not only increase our understanding of PTSD, but may also lead to more effective treatments for these patients.

The majority of neuropsychological research in PTSD uses cross-sectional designs from which it is impossible to determine whether any observed cognitive dysfunctions represent pre-trauma risk and resiliency factors or if they represent responses to the experience of trauma or PTSD. We therefore begin our review by discussing results from longitudinal and twin studies that may shed some light on this issue. We then synthesize results from cross-sectional studies concerning “frontal lobe” dysfunction associated with PTSD, focusing on simple attention and working memory, “higher-order” executive functions, flexibility, and inhibition, and the effects of emotional context on attention and executive function. The focus of this discussion will be on how difficulties regulating attention and inhibiting responses to stimuli (particularly emotional or trauma-related stimuli) could contribute to the clinical profile of PTSD—for example, leading to the development of alternative, potentially maladaptive, coping mechanisms. We will also discuss research concerning potential neural substrates of executive dysfunction, and the relationship between treatment and cognitive dysfunction, in PTSD. This review will not discuss the issue of comorbid disorders (e.g., traumatic brain injury, substance use disorders) and their potential influence on neurocognitive function in PTSD. We recognize the significant influence comorbid conditions can have on neurocognitive function and refer to recent articles focusing on this important and complex issue (Stein and McAllister, 2009, Samuelson et al., 2006).