Memory biases in the anxiety disorders: Current status

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Abstract

Information-processing models of emotional disorders suggest that anxious individuals may be characterized by a memory bias for threat-relevant information. This paper reviews and synthesizes evidence for explicit (conscious) and implicit (unconscious) memory biases in the anxiety disorders. Our review suggests variations among the anxiety disorders for explicit memory biases. Specifically, there is support for explicit memory biases for threat-relevant information in panic disorder (PD), particularly when information has been deeply encoded, but not in social phobia (SP) or generalized anxiety disorder (GAD). The few available studies suggest the presence of explicit memory biases in posttraumatic stress disorder (PTSD) and obsessive–compulsive disorder (OCD), but further research is needed. In contrast, some degree of support for implicit memory biases has been demonstrated for each of the anxiety disorders. Inconsistencies in the existing literature, topics worthy of future research attention, and directions for revising existing information-processing models of anxiety are discussed.

Introduction

The examination of memory bias in anxiety disordered individuals is important from both clinical and basic science perspectives. Intrusive memories are a common symptom of several anxiety disorders. Individuals with posttraumatic stress disorder (PTSD), for example, often experience unwanted memories through flashbacks, nightmares, and intrusive recollections of their traumatic event. Individuals with social phobia (SP) can often recount the vivid details of their self-perceived public humiliations. Individuals with panic disorder (PD) frequently experience terrifying thoughts of heart attacks, impending insanity, or even death, which may be fueled by salient memories of their first, or worst, attack. These examples suggest that anxiety disorders are characterized by heightened accessibility of threatening information. If so, they should be associated with a memory bias, or preferential memory, for threatening information. As reasonable as this hypothesis appears, when examined across anxiety disorders and types of memory, the relevant evidence is mixed.

The anxiety disorders share the primary features of anxiety and avoidance. Despite their similarities, however, there are many distinctions among them (e.g., the focus of the anxiety, comorbidity patterns, age of onset), and this heterogeneity may have contributed to inconsistent findings regarding memory biases. It is also likely that differences in methods used to study memory processes have contributed to differences in findings. Indeed, the methods that have been utilized have been as diverse as the populations studied. To date, there has not been a comprehensive examination of the empirical support for different types of memory bias in the anxiety disorders. While some reviews have been presented (e.g., Becker et al., 1999, Williams et al., 1988, Williams et al., 1997), a more comprehensive review will allow for better assessment of current knowledge and more complete delineation of areas for future exploration.

This paper is comprised of three main sections. First, we provide a general context for understanding the literature review to follow. This context includes summaries of information-processing models in general and specific to the anxiety disorders. Second, we review the evidence for explicit and implicit memory biases in each of the anxiety disorders,2 focusing on studies that have examined preferential memory for threat-relevant information among clinically anxious individuals. Each anxiety disorder is considered separately to best examine whether different clinical characteristics are related to different memory processes. Finally, possible reasons for inconsistencies in the literature are addressed and directions for future research on memory biases in the anxiety disorders are discussed. Directions for revising existing information-processing models of anxiety are considered as well.

Section snippets

Information-processing theories of emotional disorders

Information-processing models of emotional disorders suggest that anxious individuals are characterized by a memory bias for threat-relevant information. That is, they may be more likely to recall threat-relevant stimuli, either in comparison to their recall of nonthreat stimuli or in comparison to the recall of nonanxious persons. Two theories that stimulated much of the research on information processing in the anxiety disorders are A. T. Beck's theory of cognitive schemata and Bower's theory

Review of studies in Panic Disorder

Panic Disorder (PD) is characterized by recurrent and unexpected periods of intense fear or discomfort in which the person experiences a number of symptoms (e.g., palpitations, choking, nausea, fears of dying) that develop abruptly and reach their peak rapidly. Panic attacks are followed by persistent concern about having additional attacks, worry about the implications or consequences of the attack, or result in a significant change in behavior. PD can be accompanied by agoraphobia, in which

Conclusions drawn from the review

The amount of support for explicit memory biases towards threat-relevant information varies greatly by disorder. Support for explicit memory biases in individuals with PD has been demonstrated in the majority of studies in which deep-encoding procedures were utilized. Studies of explicit memory biases in PTSD and OCD appear supportive but are few in number. However, studies have generally failed to provide support for explicit memory biases for threat-relevant information in GAD or SP. In

Explaining apparent inconsistencies in the review

Although our understanding of memory processes in anxiety is increasing, there remain many inconsistencies to be resolved and new areas to be explored. It appears that there will be no simple answers to questions such as: “How is memory affected by an anxiety disorder?” Our review suggests some methodological and conceptual variables that may be particularly useful in understanding apparent discrepancies between existing studies on memory bias in the anxiety disorders: (1) the nature of the

Agenda for future research

Our review also suggests several additional areas that may be worthy of attention. Most importantly, the interplay of depressive symptoms and anxious symptoms in the expression of cognitive biases calls for much more empirical work. It will also be worthwhile to distinguish in future research on memory biases between temporary mood states and stable personality traits. Finally, influences of baseline biases in implicit memory tests should be addressed.

Implications for information-processing models of anxiety

What are the theoretical implications of the findings reviewed herein? Most generally, our review suggests that information-processing models must be modified to account for different patterns of memory biases in various anxiety disorders. This finding has great implications, as these models have not made differential predictions based on the locus of the anxiety. However, individual papers have briefly addressed these differences Cloitre et al., 1994, Lundh et al., 1997, and at least one paper

Conclusions

When examining the anxiety disorders as a group, there is little support for explicit memory biases for threat-relevant information and modest support for implicit memory biases. However, examination of results by principal diagnosis reveals that various anxiety disorders show different patterns of memory bias. Patients with PD most commonly show explicit memory biases for threat-relevant information, particularly information that has been deeply encoded. However, support for implicit memory

Acknowledgements

The authors wish to thank Drs. Mark Wheeler, Nora Newcombe, and Philip Kendall for their feedback on earlier drafts of this manuscript. The authors would also like to thank the anonymous reviewers for their helpful comments on an earlier draft of this manuscript. Preparation of this paper was supported in part by Grant No. 44119 from the National Institute of Mental Health to Richard G. Heimberg.

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