Shmuel Lissek

Attention Bias Modification Treatment: A Meta-Analysis Toward the Establishment of Novel Treatment for Anxiety

BACKGROUND Attention Bias Modification Treatment (ABMT) is a newly emerging, promising treatment for anxiety disorders. Although recent randomized control trials (RCTs) suggest that ABMT reduces anxiety, therapeutic effects have not been summarized quantitatively. METHODS Standard meta-analytic procedures were used to summarize the effect of ABMT on anxiety. With MEDLINE, January 1995 to February 2010, we identified RCTs comparing the effects on anxiety of ABMT and quantified effect sizes with Hedges d. RESULTS Twelve studies met inclusion criteria, including 467 participants from 10 publications. Attention Bias Modification Treatment produced significantly greater reductions in anxiety than control training, with a medium effect (d = .51 [corrected] (p < .001). Age and gender did not moderate the effect of ABMT on anxiety, whereas several characteristics of the ABMT training did. CONCLUSIONS Attention Bias Modification Treatment shows promise as a novel treatment for anxiety. Additional RCTs are needed to fully evaluate the degree to which these findings replicate and apply to patients. Future work should consider the precise role for ABMT in the broader anxiety-disorder therapeutic armamentarium.

Overgeneralization of Conditioned Fear as a Pathogenic Marker of Panic Disorder

OBJECTIVE Classical conditioning features prominently in many etiological accounts of panic disorder. According to such accounts, neutral conditioned stimuli present during panic attacks acquire panicogenic properties. Conditioned stimuli triggering panic symptoms are not limited to the original conditioned stimuli but are thought to generalize to stimuli resembling those co-occurring with panic, resulting in the proliferation of panic cues. The authors conducted a laboratory-based assessment of this potential correlate of panic disorder by testing the degree to which panic patients and healthy subjects manifest generalization of conditioned fear. METHOD Nineteen patients with a DSM-IV-TR diagnosis of panic disorder and 19 healthy comparison subjects were recruited for the study. The fear-generalization paradigm consisted of 10 rings of graded size presented on a computer monitor; one extreme size was a conditioned danger cue, the other extreme a conditioned safety cue, and the eight rings of intermediary size created a continuum of similarity from one extreme to the other. Generalization was assessed by conditioned fear potentiating of the startle blink reflex as measured with electromyography (EMG). RESULTS Panic patients displayed stronger conditioned generalization than comparison subjects, as reflected by startle EMG. Conditioned fear in panic patients generalized to rings with up to three units of dissimilarity to the conditioned danger cue, whereas generalization in comparison subjects was restricted to rings with only one unit of dissimilarity. CONCLUSIONS The findings demonstrate a marked proclivity toward fear overgeneralization in panic disorder and provide a methodology for laboratory-based investigations of this central, yet understudied, conditioning correlate of panic. Given the putative molecular basis of fear conditioning, these results may have implications for novel treatments and prevention in panic disorder.

Anxious responses to predictable and unpredictable aversive events

Anxiety induced by 2 types of predictable and unpredictable aversive stimuli, an unpleasant shock or a less aversive airblast to the larynx, were investigated in a between-group design. Participants anticipated predictable (signaled) or unpredictable (not signaled) aversive events, or no aversive event. Unpredictable, relative to predictable, contexts potentiated the startle reflex in the shock group but not in the airblast group. These data suggest that unpredictability can lead to a sustained level of anxiety only when the pending stimulus is sufficiently aversive. Because predictable and unpredictable danger may induce different types of aversive responses, the proposed design can serve as a useful tool for studying the neurobiology and psychopharmacology of fear and anxiety.

Generalization of Conditioned Fear-Potentiated Startle in Humans: Experimental Validation and Clinical Relevance

Though generalization of conditioned fear has been implicated as a central feature of pathological anxiety, surprisingly little is known about the psychobiology of this learning phenomenon in humans. Whereas animal work has frequently applied methods to examine generalization gradients to study the gradual weakening of the conditioned-fear response as the test stimulus increasingly differs from the conditioned stimulus (CS), to our knowledge no psychobiological studies of such gradients have been conducted in humans over the last 40 years. The current effort validates an updated generalization paradigm incorporating more recent methods for the objective measurement of anxiety (fear-potentiated startle). The paradigm employs 10, quasi-randomly presented, rings of gradually increasing size with extremes serving as CS+ and CS-. The eight rings of intermediary size serve as generalization stimuli (GSs) and create a continuum-of-similarity from CS+ to CS-. Both startle data and online self-report ratings demonstrate continuous decreases in generalization as the presented stimulus becomes less similar to the CS+. The current paradigm represents an updated and efficacious tool with which to study fear generalization--a central, yet understudied conditioning-correlate of pathologic anxiety.

Increased Anxiety During Anticipation of Unpredictable But Not Predictable Aversive Stimuli as a Psychophysiologic Marker of Panic Disorder

OBJECTIVE Predictability is a fundamental modulator of anxiety in that the ability to predict aversive events mitigates anxious responses. In panic disorder, persistent symptoms of anxiety are caused by anticipation of the next uncued (unpredictable) panic attack. The authors tested the hypothesis that elevated anxious reactivity, specifically toward unpredictable aversive events, is a psychophysiological correlate of panic disorder. METHOD Participants were exposed to one condition in which predictable aversive stimuli were signaled by a cue, a second condition in which aversive stimuli were administered unpredictably, and a third condition in which no aversive stimuli were anticipated. Startle was used to assess anxious responses to cues and contexts. RESULTS Relative to healthy comparison subjects, patients with panic disorder displayed equivalent levels of fear-potentiated startle to the threat cue but elevated startle potentiation in the context of the unpredictable condition. CONCLUSIONS Patients with panic disorder are overly sensitive to unpredictable aversive events. This vulnerability could be either a premorbid trait marker of the disorder or an acquired condition caused by the experience of uncued panic attacks. As a premorbid trait, vulnerability to unpredictability could be etiologically related to panic disorder by sensitizing an individual to danger, ultimately leading to intense fear/alarm responses to mild threats. As an acquired characteristic, such vulnerability could contribute to the maintenance and worsening of panic disorder symptoms by increasing anticipatory anxiety.

Impaired discriminative fear-conditioning resulting from elevated fear responding to learned safety cues among individuals with panic disorder

Classical fear-conditioning is central to many etiologic accounts of panic disorder (PD), but few lab-based conditioning studies in PD have been conducted. One conditioning perspective proposes associative-learning deficits characterized by deficient safety learning among PD patients. The current study of PD assesses acquisition and retention of discriminative aversive conditioning using a fear-potentiated startle paradigm. This paradigm was chosen for its specific capacity to independently assess safety- and danger learning in the service of characterizing putative anomalies in each type of learning among those with PD. Though no group difference in fear-potentiated startle was found at retention, acquisition results demonstrate impaired discriminative learning among PD patients as indexed by measures of conditioned startle-potentiation to learned safety and danger cues. Importantly, this discrimination deficit was driven by enhanced startle-potentiation to the learned safety cue rather than aberrant reactivity to the danger cue. Consistent with this finding, PD patients relative to healthy individuals reported higher expectancies of dangerous outcomes in the presence of the safety cue, but equal danger expectancies during exposure to the danger cue. Such results link PD to impaired discrimination learning, reflecting elevated fear responding to learned safety cues.

Increased anxiety during anticipation of unpredictable aversive stimuli in posttraumatic stress disorder but not in generalized anxiety disorder.

BACKGROUND Uncontrollability and unpredictability are key concepts related to re-experiencing, avoidance, and hypervigilance symptoms of posttraumatic stress disorder (PTSD). However, little is known about the differential sensitivity of PTSD individuals to unpredictable stressors, relative to either healthy individuals or individuals with other anxiety disorders. This study tested the hypothesis that elevated anxious reactivity, specifically for unpredictable aversive events, is a psychophysiological correlate of PTSD. METHODS Sixteen patients with PTSD (34.5 +/- 12.4 years) were compared with 18 patients with generalized anxiety disorder (GAD) (34.0 +/- 10.5 years) and 34 healthy control subjects (30.2 +/- 8.5 years). Participants were exposed to three conditions: one in which predictable aversive stimuli were signaled by a cue, a second in which aversive stimuli were administered unpredictably, and a third in which no aversive stimuli were anticipated. Startle magnitude was used to assess anxious responses to the threat cue and to contexts associated with each condition. RESULTS Posttraumatic stress disorder and GAD patients showed normative enhancement of fear to the predictable threat cue, but the PTSD group displayed elevated anxiety during the unpredictable condition compared with participants with GAD and healthy control subjects. CONCLUSIONS Anxious reactivity to unpredictable aversive events was heightened in PTSD but not in GAD and healthy subjects. Prior works also found signs of increased reactivity to unpredictable threat in panic disorder (PD), suggesting that PTSD and PD may involve shared vulnerability. As such, the current results inform understandings of classification, pathophysiology, and psychopharmacology of anxiety disorders, generally, and PTSD and panic disorder specifically.

Generalized Anxiety Disorder Is Associated With Overgeneralization of Classically Conditioned Fear

BACKGROUND Meta-analytic results of fear-conditioning studies in the anxiety disorders implicate generalization of conditioned fear to stimuli resembling the conditioned danger cue as one of the more robust conditioning markers of anxiety pathology. Due to the absence of conditioning studies assessing generalization in generalized anxiety disorder (GAD), results of this meta-analysis do not reveal whether such generalization abnormalities also apply to GAD. The current study fills this gap by behaviorally and psychophysiologically assessing levels of conditioned fear generalization across adults with and without GAD. METHODS Twenty-two patients with a DSM-IV-Text Revision diagnosis of GAD and 26 healthy comparison subjects were recruited and tested. The employed generalization paradigm consisted of quasi-randomly presented rings of gradually increasing size, with extreme sizes serving as conditioned danger cues (CS+) and conditioned safety cues. The rings of intermediary size served as generalization stimuli, creating a continuum of similarity between CS+ and conditioned safety cues across which to assess response slopes, referred to as generalization gradients. Primary outcome variables included slopes for fear-potentiated startle (electromyography) and self-reported risk ratings. RESULTS Behavioral and psychophysiological findings demonstrated overgeneralization of conditioned fear among patients with GAD. Specifically, generalization gradients were abnormally shallow among GAD patients, reflecting less degradation of the conditioned fear response as the presented stimulus differentiated from the CS+. CONCLUSIONS Overgeneralization of conditioned fear to safe encounters resembling feared situations may contribute importantly to the psychopathology of GAD by proliferating anxiety cues in the individuals environment that are then capable of evoking and maintaining anxiety and worry associated with GAD.

TOWARD AN ACCOUNT OF CLINICAL ANXIETY PREDICATED ON BASIC, NEURALLY MAPPED MECHANISMS OF PAVLOVIAN FEAR‐LEARNING: THE CASE FOR CONDITIONED OVERGENERALIZATION

The past two decades have brought dramatic progress in the neuroscience of anxiety due, in no small part, to animal findings specifying the neurobiology of Pavlovian fear‐conditioning. Fortuitously, this neurally mapped process of fear learning is widely expressed in humans, and has been centrally implicated in the etiology of clinical anxiety. Fear‐conditioning experiments in anxiety patients thus represent a unique opportunity to bring recent advances in animal neuroscience to bear on working, brain‐based models of clinical anxiety. The current presentation details the neural basis and clinical relevance of fear conditioning, and highlights generalization of conditioned fear to stimuli resembling the conditioned danger cue as one of the more robust conditioning markers of clinical anxiety. Studies testing such generalization across a variety of anxiety disorders (panic, generalized anxiety disorder, and social anxiety disorder) with systematic methods developed in animals will next be presented. Finally, neural accounts of overgeneralization deriving from animal and human data will be described with emphasis given to implications for the neurobiology and treatment of clinical anxiety.

Development of anxiety: the role of threat appraisal and fear learning

Anxious individuals exhibit threat biases at multiple levels of information processing. From a developmental perspective, abnormal safety learning in childhood may establish threat‐related appraisal biases early, which may contribute to chronic disorders in adulthood. This review illustrates how the interface among attention, threat appraisal, and fear learning can generate novel insights for outcome prediction. This review summarizes data on amygdala function, as it relates to learning and attention, highlights the importance of examining threat appraisal, and introduces a novel imaging paradigm to investigate the neural correlates of threat appraisal and threat‐sensitivity during extinction recall. This novel paradigm can be used to investigate key questions relevant to prognosis and treatment. Depression and Anxiety, 2011.© 2010 Wiley‐Liss, Inc.