Predicting clinical outcomes via human fear conditioning: A narrative review

Self-report measures of fear learning and extinction and their association with internet-based cognitive behavioural therapy outcome

Despite the widespread use of cognitive-behavioural therapy (CBT), only about half of patients respond favourably. Understanding whether relevant psychological processes are associated with treatment response could help identify patients at risk of non-response prior to treatment and improve their outcomes by enabling clinicians to tailor interventions accordingly. Fear conditioning tasks are a valuable tool for studying the learning processes associated with anxiety disorders and their treatment. This study examined associations between outcomes from a remote fear conditioning task and responses to internet-based CBT. Anxious adults (n = 112) completed a fear conditioning task before receiving internet-based CBT. Participants rated their expectancy of an aversive noise (unconditioned stimulus; US) in response to a reinforced conditional stimulus (CS+) and a nonreinforced conditional stimulus (CS-) during acquisition, followed by extinction where neither stimulus was reinforced. Anxiety symptoms were assessed before each CBT session. Linear regression models indicated no significant association between mean US-expectancy ratings for 'safe' stimuli (acquisition CS- and extinction CS+) and change in anxiety across treatment. These findings contribute to the mixed literature on fear conditioning's role in treatment outcomes, highlighting the need for further research to elucidate the complex interplay between fear conditioning processes and response to CBT in anxiety disorders.

Fear and safety learning in anxiety- and stress-related disorders: An updated meta-analysis

Fear learning processes are believed to play a crucial role in the development and maintenance of anxiety and stress-related disorders. To integrate results across different studies, we conducted a systematic meta-analysis following PRISMA guidelines to examine differences in fear conditioning during fear acquisition, extinction, and extinction recall between individuals with anxiety-related or stress-related disorders and healthy participants. This analysis updates the work of Duits et al. (2015) while also refining distinctions between physiological and behavioral outcomes and examining extinction recall. Our meta-analysis encompasses 77 studies published from 1986 to 2022, involving 2052 patients with anxiety disorders, obsessive-compulsive disorder, or post-traumatic stress disorder, and 3258 healthy controls. The results indicate significant differences in fear acquisition, extinction, and recall between the two groups. Specifically, during acquisition patients exhibited heightened physiological and behavioral responses to the CS- and reported increased affect ratings for the CS+ . During extinction and extinction recall, patients continue to show heightened threat expectancy and negative affect ratings towards the CS- and increased affect ratings towards the CS+ . No differences were found in CS+ /CS- differentiation between groups. These findings imply that individuals with anxiety and stress-related disorders may exhibit amplified responses to safety cues and stronger reactions to threat cues during fear conditioning, lasting through extinction and extinction recall. These changes may lead to increased sensitivity in detecting fear and slower extinction process, resulting in more enduring anxiety responses. We discuss these results in the context of existing literature on fear and safety learning and consider potential underlying mechanisms.

Stage 2 Registered Report: Propositional Thought Is Sufficient for Imaginal Extinction as Shown by Contrasting Participants With Aphantasia, Simulated Aphantasia, and Controls

Imaginal exposure is a standard procedure of cognitive behavioral therapy for the treatment of anxiety and panic disorders. It is often used when in vivo exposure is not possible, too stressful for patients, or would be too expensive. The Bio-Informational Theory implies that imaginal exposure is effective because of the perceptual proximity of mental imagery to real events, whereas empirical findings suggest that propositional thought of fear stimuli (i.e., thinking about the stimuli without seeing them in the mind's eye) could be sufficient. To investigate whether mental imagery or propositional thought is crucial for the success of imaginal exposure, participants with the rare state of aphantasia (= absence of sensory mental imagery) and two control groups were subjected to a fear conditioning paradigm followed by imaginal exposure and a reinstatement procedure. During imaginal exposure, a control group (N = 30) stared at a bright screen to disrupt visual imagery by incoming luminance (=simulated aphantasia), while a second control group (N = 30) and participants with actual aphantasia (N = 30) kept their eyes closed. Results showed successful extinction in all groups, thus demonstrating that imaginal extinction is possible using propositional thought. Moreover, exploratory analyses revealed less subjective fear in people with aphantasia during the fear conditioning procedure, potentially due to similar mechanisms as in alexithymia, that is, a decoupling between physiological arousal and emotional experience.

Predicting Emotional Distress, Based on Acquisition, Extinction, Avoidance, and Generalization Learning

This prospective study aimed to investigate whether fear conditioning parameters measured at baseline could predict the development of emotional distress over a 6-month period among 655 first-year university students. Verbal and behavioral measures of acquisition, extinction, avoidance, and generalization were obtained through an online task at the start of the academic year. Emotional distress was evaluated 4 to 6 months later, with questionnaires assessing anxiety, stress, depression, and coping trajectories. Initial analyses explored the interplay of conditioning parameters at baseline, hypothesizing that the corresponding learning processes may mutually reinforce each other, contributing to distinct vulnerabilities for emotional distress. Although no distinct profiles based on conditioning processes were identified, the analyses did uncover correlations between increased acquisition and avoidance of conditioned threat stimuli and reduced extinction, avoidance of safe stimuli, and generalization. Subsequent main analyses related the processes and their interactions to the development of emotional distress. Findings suggest that acquiring fear toward conditioned safety and threat stimuli, as well as avoiding conditioned threat stimuli, may be predictive of higher levels of emotional distress. Analyses relating extinction and generalization to emotional distress revealed mostly nonsignificant findings, emphasizing the need for methodological scrutiny in identifying anxiety-related learning indices. This research contributes to understanding individual differences in the development of emotional distress and informs future investigations into learning processes and their implications for mental health.

Overgeneralization of conditioned fear in patients with social anxiety disorder

Introduction

While abnormal responses to threat, including overgeneralization to conditioned fear, have been postulated to play a critical role in pathological anxiety, the relevance of previous findings to social anxiety disorder (SAD) is unclear. We investigated conditioned and generalized fear responses in patients with SAD using socially relevant stimuli.

Methods

A total of 26 patients with SAD and 25 healthy controls participated in a fear conditioning and generalization paradigm consisting of two neutral faces as conditioned stimuli (CS+ or CS-) and an angry face with contemptuous comments as unconditioned stimuli. Eight morphed faces of two conditioned stimuli in each continuum were given to test generalization. Behavioral data and physiological responses were acquired.

Results

Successful conditioning was observed in the risk ratings for both groups, while only a marginal indication of conditioning was noted in physiological measures. During the generalization phase, patients rated the risk higher than CS- when the stimuli close to CS- contained a portion of CS+ features. Larger skin conductance responses to this stimulus were linked to higher fear of negative evaluation. In addition, patients spent a longer time evaluating safe and ambiguous stimuli than healthy controls and exhibited consistently high levels of subjective arousal.

Discussion

Taken together, our findings suggest that SAD patients may exhibit a tendency towards overgeneralization of fear responses and show distinct patterns in processing generalized threat stimuli compared to healthy controls. Even though overgeneralization was not evident in physiological measures, it is necessary to consider this behavioral characteristic in the clinical management of patients with SAD.

Unconditioned stimulus devaluation decreases the generalization of costly safety behaviors

Safety behaviors are often maladaptive in clinical anxiety as they typically persist without realistic threat and cause various impairments. In the laboratory, safety behaviors are modelled by responses to a conditioned stimulus (CS) that reduce the occurrence of an expected aversive unconditioned stimulus (US). Preliminary evidence suggests that US devaluation, a procedure that decreases US aversiveness, devalues the threat value of the CS and thus diminishes safety behaviors to the CS. This study (n = 78) aimed to extend this finding and examined whether US-devaluation can reduce the generalization of safety behaviors to various stimuli. After acquiring safety behaviors to CSs of different categories, the US predicted by one CS category was devalued. In test, participants showed a selective reduction in safety behaviors to novel stimuli of the devalued CS category, reflecting a decrease in generalization of safety behaviors. Trait anxiety was associated with persistent generalized safety behaviors to novel stimuli of the devalued category. We discuss how US devaluation may improve treatment outcome but also the challenges of clinical translation.

Enhanced late positive potential to conditioned threat cue during delayed extinction in anxious youth

BACKGROUND

Deficits in threat learning relate to anxiety symptoms. Since several anxiety disorders arise in adolescence, impaired adolescent threat learning could contribute to adolescent changes in risk for anxiety. This study compared threat learning among anxious and non-anxious youth using self-reports, peripheral psychophysiology measures, and event-related potentials. Because exposure therapy, the first-line treatment for anxiety disorders, is largely based on principles of extinction learning, the study also examined the link between extinction learning and treatment outcomes among anxious youth.

METHODS

Clinically anxious (n = 28) and non-anxious (n = 33) youth completed differential threat acquisition and immediate extinction. They returned to the lab a week later to complete a threat generalization test and a delayed extinction task. Following these two experimental visits, anxious youth received exposure therapy for 12 weeks.

RESULTS

Anxious as compared to non-anxious youth demonstrated elevated cognitive and physiological responses across acquisition and immediate extinction learning, as well as greater threat generalization. In addition, anxious youth showed enhanced late positive potential response to the conditioned threat cue compared to the safety cue during delayed extinction. Finally, aberrant neural response during delayed extinction was associated with poorer treatment outcomes.

CONCLUSIONS

The study emphasizes differences between anxious and non-anxious youth in threat learning processes and provides preliminary support for a link between neural processing during delayed extinction and exposure-based treatment outcome in pediatric anxiety.

Let's play pretend: Towards effective modelling in experimental psycho(patho)logy

BACKGROUND AND OBJECTIVES

Models are omnipresent in science. We introduce a novel framework to achieve more effective modelling practices in general psychology and experimental psychopathology.

METHOD

We analyze three types of models that are common in psychology: laboratory models, computational models, and cognitive models. We then evaluate two common ways to assess the translational value of models (phenomenological similarity and deep similarity) as well as an arguably underappreciated way (functional similarity). Functional similarity is based on an assessment of whether variables (e.g., the administration of a pharmacological substance) have a similar effect (a) in the model (e.g., in a fear conditioning procedure) and (b) on the real-life target phenomenon (e.g., on real-life anxiety complaints).

CONCLUSIONS

We argue that the assessment of functional similarity is a powerful tool to assess the translational value of models in the field of experimental psychopathology and beyond.

Calibrating your own fears: Feasibility of a remote fear conditioning paradigm with semi-subjective stimulus calibration and differences in fear learning

Fear conditioning studies have occurred mostly in the laboratory, but recently researchers have started to adapt fear conditioning procedures for remote application. Standardization of aversive stimulus material not causing unnecessarily strong discomfort remains an issue especially relevant to research without experimental supervision. The present study introduces a novel semi-subjective method to calibrate aversive sounds in a remotely conducted fear conditioning paradigm. To demonstrate feasibility and proof of concept, 165 participants completed the paradigm, calibrating the loudness of an aversive sound without the guidance of an experimental instructor. This study also aimed to replicate existing findings of participant groups that differed in their early CS-UCS contingency awareness. Participants were classified as Accurate (UCS more likely after the CS+ than CS-), Poor (UCS more likely after the CS- than CS+, or UCS unlikely after either CS), and Threat Biased (UCS equally likely after the CS+ and CS-). Results indicated both the feasibility and efficacy of the paradigm, with participants showing typical patterns of fear learning. Threat Biased participants showed significantly higher uncertainty towards safety signals. There were no differences between the groups in terms of personality traits, thus questioning whether these attributes mediate differences in fear learning and the emergence of anxiety disorders. Using semi-subjective sound calibration appears to be functional, and future studies may consider implementing the new method when remotely administering fear conditioning paradigms.

Using pre-treatment de novo threat conditioning outcomes to predict treatment response to DCS augmentation of exposure-based CBT

BACKGROUND

Over a decade and a half of research has resulted in inconsistent evidence for the efficacy of d-cycloserine (DCS), a partial glutamatergic N-methyl-D-aspartate agonist, for augmenting exposure-based cognitive behavioral therapy (CBT) for anxiety- and fear-based disorders. These variable findings have motivated the search for moderators of DCS augmentation efficacy.

METHODS

In this secondary analysis of a previous randomized clinical trial, we evaluated the value of de novo threat conditioning outcomes-degree of threat acquisition, extinction, and extinction retention-for predicting treatment response to exposure-based CBT for social anxiety disorder, applied with and without DCS augmentation in a sample of 59 outpatients.

RESULTS

We found that average differential skin conductance response (SCR) during extinction and extinction retention significantly moderated the prediction of clinical response to DCS: participants with poorer extinction and extinction retention showed relatively improved treatment response with DCS. No such effects were found for expectancy ratings, consistent with accounts of DCS selectively aiding lower-order but not higher-order extinction learning.

CONCLUSIONS

These findings provide support for extinction and extinction retention outcomes from threat conditioning as potential pre-treatment biomarkers for DCS augmentation benefits. Independent of DCS augmentation, the current study did not support threat conditioning outcomes as useful for predicting response to exposure-based CBT.

Fear learning and extinction predicts anxiety in daily life: a study of Pavlovian conditioning and ecological momentary assessment

BACKGROUND

The association between anxious mood and aberrant fear learning mechanisms has not been fully elucidated. Studying how fear conditioning and extinction constructs relate to anxiety symptoms and reactivity to stressful and benign moments in everyday life provides a powerful addition to experimental paradigms.

METHOD

Fifty-one young adults completed laboratory-based differential conditioning and extinction tasks with (CS + ) and without (CS-) an aversive unconditional stimulus (US). Electrodermal skin conductance responses were measured during each phase, followed by ecological momentary assessment (EMA) tapping anxiety and stressors six times daily for seven days (2, 142 moments).

RESULTS

Conditioned electrodermal reactivity to the CS + and overgeneralisation to the CS- were associated with greater change in anxiety (measured via EMA), across non-stressful situations, remaining the same across stressful situations. Likewise, during extinction when the CS + is now safe, more electrodermal reactivity to the CS + was associated with more anxiety change across non-stressful situations and remained the same across stressful situations. Also, during extinction when threat is absent, more electrodermal reactivity at the late stage of the CS- was associated with less momentary anxiety change in response to stressful situations; more electrodermal activity at the late stage of the CS + was associated with more anxiety change across non-stressful situations and remained the same across stressful situations.

CONCLUSIONS

Sampling 'in vivo' emotion and stress experiences, study findings revealed links between conditioned electrodermal reactivity and overgeneralisation to safe stimuli and heightened anxious reactivity during non-stressful (i.e. safe) moments in daily life, coupled with less change in response to actual stressors.

Challenges and considerations for treating PTSD with medicinal cannabis: the Australian clinician's perspective

INTRODUCTION

Preclinical and experimental research have provided promising evidence that medicinal cannabis may be efficacious in the treatment of posttraumatic stress disorder (PTSD). However, implementation of medicinal cannabis into routine clinical therapies may not be straightforward.

AREAS COVERED

In this review, we describe some of the clinical, practical, and safety challenges that must be addressed for cannabis-based treatment of PTSD to be feasible in a real-world setting. These issues are especially prevalent if medicinal cannabis is to be combined with trauma-focused psychotherapy.

EXPERT OPINION

Future consideration of the clinical and practical considerations of cannabis use in PTSD therapy will be essential to both the efficacy and safety of the treatment protocols that are being developed. These issues include dose timing and titration, potential for addiction, product formulation, windows of intervention, and route of administration. In particular, exposure therapy for PTSD involves recall of intense emotions, and the interaction between cannabis use and reliving of trauma memories must be explored in terms of patient safety and impact on therapeutic outcomes.

Understanding clinical fear and anxiety through the lens of human fear conditioning

Fear is an adaptive emotion that mobilizes defensive resources upon confrontation with danger. However, fear becomes maladaptive and can give rise to the development of clinical anxiety when it exceeds the degree of threat, generalizes broadly across stimuli and contexts, persists after the danger is gone or promotes excessive avoidance behaviour. Pavlovian fear conditioning has been the prime research instrument that has led to substantial progress in understanding the multi-faceted psychological and neurobiological mechanisms of fear in past decades. In this Perspective, we suggest that fruitful use of Pavlovian fear conditioning as a laboratory model of clinical anxiety requires moving beyond the study of fear acquisition to associated fear conditioning phenomena: fear extinction, generalization of conditioned fear and fearful avoidance. Understanding individual differences in each of these phenomena, not only in isolation but also in how they interact, will further strengthen the external validity of the fear conditioning model as a tool with which to study maladaptive fear as it manifests in clinical anxiety.

Is Fear Extinction Impairment Central to Psychopathology?

As discussed in this chapter, there have been enormous advances in our understanding of how anxiety disorders develop, are maintained, and can be treated. Many of these advances have been the result of translational studies using fear conditioning and extinction models. Despite these successes, we recognize, as a field, that there are important limitations in the extent to which extinction can explain how anxiety disorders and behaviors remit. Clinically speaking, the outstanding challenge for treatment of anxiety disorders is to improve the current suboptimal success rates. Over the past 30 years, we have not improved our treatment success rates despite employing many pharmacological and pharmacological strategies. While extinction and related fear circuitry mechanisms most certainly appear to play a role in treatment of anxiety disorders, they are also apparently insufficient to fully accommodate the varied responses individuals exhibit with this treatment approach. Increasingly diverse and innovative approaches are needed that accommodate the multitude of change mechanisms involved in treating anxiety. However, this is not to suggest ignoring the key role that extinction and memory updating processes play in overcoming anxiety.

Fear conditioning and extinction learning in the mood and anxiety disorders spectrum - Associations with the outcome of cognitive behavior therapy

In the current study, we test for the specificity of deficits in fear acquisition and extinction for the anxiety disorders spectrum. We compared fear acquisition and fear extinction learning between a group of patients with either an anxiety disorder (n = 93) or depression (n = 103) attending for treatment in our outpatient center and a sample of healthy control participants (n = 60). To assess the specificity of the predictive validity of extinction learning and safety learning for the outcome of exposure-based treatments, patients additionally underwent disorder-specific cognitive behavior therapy (CBT). We found only very little evidence for differences in safety or extinction learning between healthy controls and patients with anxiety-disorders or depression using both a group-based categorical analytic approach, as well as a trans-diagnostic, dimensional analytic approach. On the contrary, for anxiety patients only, more favorable extinction learning and more favorable safety learning was associated with more favorable treatment outcome. In sum, this specific prediction of treatment outcome in anxiety patients confirms and extends current theoretical models of exposure-based treatments for anxiety disorders, but does not support the notion of general extinction learning deficits in the anxiety disorders spectrum.

Neuroimaging of Fear Extinction

Extinguishing fear and defensive responses to environmental threats when they are no longer warranted is a critical learning ability that can promote healthy self-regulation and, ultimately, reduce susceptibility to or maintenance of affective-, trauma-, stressor-,and anxiety-related disorders. Neuroimaging tools provide an important means to uncover the neural mechanisms of effective extinction learning that, in turn, can abate the return of fear. Here I review the promises and pitfalls of functional neuroimaging as a method to investigate fear extinction circuitry in the healthy human brain. I discuss the extent to which neuroimaging has validated the core circuits implicated in rodent models and has expanded the scope of the brain regions implicated in extinction processes. Finally, I present new advances made possible by multivariate data analysis tools that yield more refined insights into the brain-behavior relationships involved.

The influence of sleep on fear extinction in trauma-related disorders

In Posttraumatic Stress Disorder (PTSD), fear and anxiety become dysregulated following psychologically traumatic events. Regulation of fear and anxiety involves both high-level cognitive processes such as cognitive reattribution and low-level, partially automatic memory processes such as fear extinction, safety learning and habituation. These latter processes are believed to be deficient in PTSD. While insomnia and nightmares are characteristic symptoms of existing PTSD, abundant recent evidence suggests that sleep disruption prior to and acute sleep disturbance following traumatic events both can predispose an individual to develop PTSD. Sleep promotes consolidation in multiple memory systems and is believed to also do so for low-level emotion-regulatory memory processes. Consequently sleep disruption may contribute to the etiology of PTSD by interfering with consolidation in low-level emotion-regulatory memory systems. During the first weeks following a traumatic event, when in the course of everyday life resilient individuals begin to acquire and consolidate these low-level emotion-regulatory memories, those who will develop PTSD symptoms may fail to do so. This deficit may, in part, result from alterations of sleep that interfere with their consolidation, such as REM fragmentation, that have also been found to presage later PTSD symptoms. Here, sleep disruption in PTSD as well as fear extinction, safety learning and habituation and their known alterations in PTSD are first briefly reviewed. Then neural processes that occur during the early post-trauma period that might impede low-level emotion regulatory processes through alterations of sleep quality and physiology will be considered. Lastly, recent neuroimaging evidence from a fear conditioning and extinction paradigm in patient groups and their controls will be considered along with one possible neural process that may contribute to a vulnerability to PTSD following trauma.

Extinction learning as pretrauma vulnerability factor of posttraumatic stress: a replication study

BACKGROUND

Learning tasks have been used to predict why some, and not others, develop posttraumatic stress disorder (PTSD) after exposure to a traumatic event. There is some evidence from prospective studies in high risk profession samples that reduced extinction learning might represent a marker or even a vulnerability factor for PTSD development.

OBJECTIVE

Since the evidence is scarce, the aim of this study was to perform a conceptual replication of an earlier prospective study, testing whether pretrauma extinction learning predicts later PTSD symptom severity.

METHOD

A sample of 529 fire fighters performed a conditioning task at baseline and filled out questionnaires to assess PTSD symptom severity and neuroticism. At six and 12 months follow-up, exposure to stressful events and PTSD symptom severity were measured.

RESULTS

Results indicate that previous findings were not replicated: although reduced extinction learning was associated with higher PTSD symptom severity at baseline, extinction learning did not predict PTSD symptom severity at follow-up. Only PTSD symptom severity at baseline and stressor severity predicted PTSD symptom severity at follow-up.

CONCLUSIONS

Since earlier findings on the predictive value of pre-trauma extinction learning on PTSD symptom severity were not replicated, extinction learning might not be a general risk factor PTSD for all individuals. More prospective studies including multiple factors seem needed to unravel the complex relationships of these factors influencing PTSD development.

HIGHLIGHTS

Reduced extinction learning correlated with higher PTSD symptom severity at baseline.Reduced extinction learning did not predict PTSD symptom severity at follow-up.The predictive effect of pre-trauma extinction learning on PTSD was not replicated.

COVID-19-related distress is associated with analogue PTSD symptoms after exposure to an analogue stressor

Background: The COVID-19 outbreak in early 2020 was associated with an immediate increase in mental health problems in a significant percentage of the general population. Therefore, it is crucial to investigate how the COVID-19 pandemic - as a psychosocial stressor - affected the aetiological processes of mental disorders. Previous research has shown that stress potentiates associative (fear) learning and analogue symptoms of posttraumatic stress disorder (PTSD) and that analogue PTSD symptoms can emerge in response to associative learning. Objective: We investigated whether distress in response to the COVID-19 outbreak support the development of intrusions and rumination after exposure to a non-COVID-19-related analogue trauma. Moreover, we examined if these effects are mediated by the strength of associative learning during analogue trauma. Method: 122 undergraduate university students participated in an online experiment between March and July 2020. They completed questionnaires measuring distress and rumination related to the COVID-19 outbreak. On a subsequent day, they went through an associative learning task, in which neutral stimuli were paired with the appearance of a highly aversive film clip. Subjective ratings were assessed as indicators of associative learning. On the next day, participants documented film-related intrusions and rumination. Results: COVID-19-related distress but not rumination was associated with post-film intrusion and rumination load. These effects were mediated by associative learning. Conclusions: The current findings are in line with the assumptions that stress enhanced both associative learning and PTSD symptoms. Specifically, they indicate that prolonged psychosocial stress - like during the COVID-19 outbreak - is linked to individual differences in memory processing of aversive events. Further confirmatory research is needed to replicate these results.