Test of an Inhibitory Learning Model of Extinction in Treatment of Anxious Youth

Exposure therapy-which involves repeatedly exposing individuals to feared situations to change their fear responses to and beliefs about those situations--has been a mainstay of treatments for anxiety disorders since it was developed in the 1950s. Today, exposure therapy is the most commonly-occurring treatment technique included in well-supported treatments for anxiety disorders, and meta-analyses have indicated that exposure is more strongly associated with treatment gains in anxious youth compared to non-behavioral interventions. Despite its effectiveness, approximately 40% of anxious youth fail to achieve clinically significant benefit from exposure therapy. This indicates that further research is needed regarding strategies for optimizing exposure therapy so that it is effective for a greater proportion of youth.

There is clearly a need to optimize exposure therapy for youth, but at the same time very little empirical data exists regarding how exposure works or the best way to conduct exposures. Common wisdom about exposure, based on emotional processing theory, dictates that exposure works by breaking and eliminating conditioned fear responses through a process called habituation. This viewpoint dictates that exposure should be conducted until habituation occurs (i.e., until a physiological fear response reduces by at least 50%), and that habituation both during and between exposure sessions is necessary for improvement. As exposure therapy has evolved, other common practices have emerged that lack clear evidence supporting their efficacy. For example, it is common clinical practice to encourage youth to challenge their thoughts about a feared situation before and during an exposure (i.e., cognitive restructuring), even though clear evidence does not exist to support this practice. Additionally, it is common for clinicians to create a "fear ladder" or "hierarchy" with patients before beginning exposures. This hierarchy typically takes the form of a rank-ordered list of exposures or feared stimuli from least to most difficult, and clinicians move up this list systematically from the easiest to most difficult items during treatment. Again, there is little clear evidence to support this practice.

More recent research on fear extinction indicates that exposure therapy does not cause threat associations to disappear but rather leads to the formation of non-threat (i.e., inhibitory) associations that compete with and weaken older threat associations. The goal of exposure therapy, according to this model, is to strengthen these non-threat associations and weaken threat associations. Research on inhibitory learning has turned many of the long-standing exposure practices discussed in the previous paragraph on their head by providing new guidelines for optimizing exposure therapy. Many of these new guidelines differ significantly from common clinical practices and are designed to maximize learning of inhibitory associations. These guidelines are as follows:

1. Design exposures that maximally violate a patient's expectations about how bad an outcome would be or how often it will occur. In clinical practice, an exposure that maximally violates expectancies is one that is terminated not when fear habituates or reduces by a certain amount (e.g., "What is your fear rating?") but rather when the patient's expectancy of a bad outcome is significantly reduced. (e.g., "What do you think the chances are that X will happen?).
2. Do not instruct patients to change their thinking about a feared situation before or during and exposure. The principle of maximum violation of expectancies dictates that participants should not be encouraged to use cognitive reappraisal (e.g., strategies for thinking more realistically or accurately) during an exposure, as such strategies reduce the expectation that a negative outcome will occur and thus prevent maximum violation of expectancy.
3. Introduce variability of stimuli into exposure tasks by moving up and down a fear ladder randomly. Inhibitory learning theory suggests that clinicians should frequently vary the difficulty of exposure to stimuli to create a consistently high level of emotion, which has been associated with superior extinction learning. This guideline means that, instead of moving up a fear hierarchy or ladder in a systematic way from least to most difficult over time, and moving on to more difficult items after habituation to easier ones has occurred, clinicians should design exposures that will allow patients to achieve variable but generally high levels of fear or anxiety over the full course of an exposure.

In this study, the investigators plan to test these clinical practice guidelines derived from inhibitory learning against standard exposure practice. A few studies have empirically tested these and/or other clinical practice guidelines established based on inhibitory learning in clinical adult samples. However, no known studies have yet empirically tested the efficacy of an inhibitory learning approach to exposure therapy in youth with anxiety or other emotional disorders, nor have any known studies tested the acceptability or feasibility of such an approach. Therefore, in this study the investigators propose to conduct a small-scale, pilot randomized controlled trial (RCT) examining the feasibility, acceptability, and relative efficacy of applying an inhibitory learning approach to exposure in youth. Up to 20 youth will be randomized to one of two groups-standard exposure (SE) or exposure conducting according to inhibitory learning principles (E + IL). Given the small n for this study, the primary goal will be to assess feasibility and acceptability of an inhibitory learning approach to exposure, while establishing the efficacy of this approach relative to SE is exploratory. This study, along with planned larger-scale RCTs to follow, will help to inform clinical care guidelines for best practice of exposure therapy with anxious youth.