Part 1: Habituation during ERP treatment: Always appreciated, never expected

** Special thanks to one of my clients for the title of this post **

If you have any familiarity with obsessive-compulsive disorder (OCD) and exposure and response prevention treatment (ERP), then you’ve almost certainly heard the term habituation. 

Here’s a simplified, but quick and easy, way of thinking about habituation:

Have you ever jumped into a cold lake? How’d it feel? Cold at first. Perhaps even uncomfortably cold. What happened when you stayed in the water for ten minutes? Or maybe just two or three minutes. You got used to it. You probably got to the point where you didn’t further notice the temperature of the water. 

Did your body heat up the temperature of the lake and that’s why you didn’t notice the temperature anymore? Of course not. Your body got used to the temperature and you were free to swim and splash.

In the context of OCD, and put more clinically, habituation is the process by which a person's emotional and physiological response to a “trigger” (a feared stimulus) naturally decreases over time through repeated, prolonged exposure to that stimulus (combined with abstaining from the use of avoidance or escape behaviors).

For example: Does your anxiety activate when touching a door knob? Then a typical exposure within ERP will include touching door knobs. Although your anxiety will probably activate when you initially touch the door knob, the longer you do it, the more likely you’ll experience a natural reduction in your anxiety – the more likely you’ll habituate. 

Frequently, I have clients who’ve previously participated in ERP tell me that they’ve been told that the purpose of doing ERP is to “face your fear until it doesn’t scare you anymore” and that “if they just stay in the exposure (e.g. keep touching the door knob), their anxiety will go away”. 

It’s true that doing things that make you anxious is part of ERP. And it’s true that staying in the exposure for prolonged periods of time, even if you’re anxious (even very anxious), is part of ERP. However, “facing your fear until you’re not scared anymore” or “doing exposures until the anxiety goes away” is:

1. An overly simplistic account of what’s occurring during an exposure 

2. Wrong in a very important way.

To understand how come I say this is an over simplistic and wrong account of what’s occurring during an exposure, in part 1 of this series, we’ll briefly review the history of ERP. This will help us see how come the “face your fear until it doesn’t scare you anymore” idea is partially correct. Then, in part 2, we’ll review the more up-to-date way of thinking about what’s going on inside of ERP. 

---

The History of ERP

Until the mid-1960s, if you sought treatment for OCD (assuming you could find a professional who knew what OCD was), you’d almost certainly be told that OCD is an untreatable condition.¹ This began to change with an initial breakthrough in 1966. Victor Meyer, a psychiatrist at the Middlesex Hospital Medical School in London, published an article describing two case studies.² The case studies described two women, both exhibiting symptoms of OCD, who had not experienced meaningful success with previous treatments. Their symptoms were so severe that both were considering lobotomy (it was that long ago). 

The first woman was experiencing obsessions and compulsions around contamination. The second woman was experiencing obsession and compulsions around blasphemous thoughts. Meyer supported them during treatment, continually guiding them through participation in activities that activated their anxiety (exposures). Crucially, Meyer worked with both clients in abstaining from the rituals the clients normally used to reduce the obsessions and anxiety after having participated in the exposure tasks (this is the response prevention portion of exposure treatment). Meyer reported good, life-saving results of the treatment for both women and suggested that other treatment providers consider a similar treatment strategy.

Meyer continued his work and other researchers followed his lead throughout the 1970s. This included the first controlled studies which found similar promising results.³ Although exposure and response prevention was involved in these studies, the researchers reported uncertainty around why response prevention appeared related to successful treatment.

A hallmark moment in OCD and ERP treatment was the 1986 publication of the article “Emotional processing of fear: Exposure to corrective information” in the prestigious journal Psychological Bulletin.⁴ By 1986, it was already well established that ERP was an effective treatment for OCD. What made Foa and Kozak’s 1986 article so important was its comprehensive description of the mechanisms of ERP (how come ERP is effective). 

The umbrella term Foa and Kozak used to describe these mechanisms was “emotional processing theory” and that’s what we’ll turn to now.

Edna B. Foa, Ph.D.

Emotional Processing Theory:

Foa and Kozak’s 1986 article presented a possible mechanism for how come ERP was effective at treating OCD. They suggested that ERP worked by activating a fear structure and then presenting new information incompatible with the fear structure which results in new learning. 

Let’s break down what they mean step by step.

The first concept to understand is the idea of a fear structure. Fear is a natural and helpful human emotion. In most (but not all) cases, fear is learned. Learning involves memory. Foa and Kozak elaborated on this when they described a fear structure as involving specific fear-inducing stimuli that are represented in memory via a particular structural network which includes information about the feared stimuli (e.g., door knobs might be contaminated), information about fear responses related to the stimuli (e.g., when I touch door knobs, I get thoughts about contamination and get anxious), and the meaning of this information (e.g., I might get sick; I might get stuck with these thoughts and feelings forever). 

Foa and Kozak further reviewed that the various components of the fear structure act as a network, meaning that activation of any element could activate the entire network (e.g., feeling anxious might activate thoughts of contamination in the same way that thoughts of contamination might activate feelings of anxiety – and both are related to urges to wash).  

They went on to describe that in anxiety disorders like OCD, PTSD, etc., a fear structure is present and this fear structure is “pathological”. By “pathological” they meant that the fear structure is activating all the characteristic components of fear (e.g., physiological arousal, biased attentional processes, etc) even though there is no realistic danger. Because there is no realistic danger, the fear structure needs to be modified in order for the individual to be able to more freely engage in their life without the distracting and painful activation of that structure. 

Unfortunately, the modification of the fear structure does not occur simply by identifying its existence and its disproportionate and dysfunctional activation. Instead, modification of the fear structure requires emotional processing. For emotional processing to occur, two elements are required:

1. Activation of the fear structure

2. Incorporation of new information which is incompatible with the pathological elements of the fear structure.

ERP and Emotional Processing:

Let’s explore an example of ERP to make more clear how it involves emotional processing. 

Imagine that an individual with a contamination related theme area is participating in ERP. This individual’s contamination themes include, among other things, the belief that if they touch something that might be contaminated, then they will get stuck with intrusive, distracting thoughts and related painful, anxious feelings that last forever unless they decontaminate (e.g., washing compulsion). As you might have guessed, they also become concerned with cross-contaminating other items because of what that cross-contamination might mean for them (e.g., future intrusive thoughts and anxious feelings associated with possibly contacting the cross-contaminated item).

During an ERP exercise, the individual comes into contact with a contaminated object (e.g., a trash can). Touching the object activates the fear structure, including thoughts about contamination, anxious feelings (and physiological arousal of these anxious feelings like elevated heart rate, shortness of breath, muscle tension, etc), and expectations that the thoughts and feelings will last forever unless they decontaminate. 

However, over time, as the individual maintains contact with the contaminated object and allows the thoughts and feelings to be present, they notice a decrease in the intensity of the intrusive thoughts and anxious feelings. This reduction in intrusive thoughts and anxious feelings provides the individual direct contact with the new information that the intrusive thoughts and anxious feelings did not last forever. This new information contradicts the information within the fear structure that the feelings would last forever. 

As a result, this new information, obtained via the ERP exercise, results in new learning which gets stored into memory and, ultimately, results in new expectations (e.g., if I touch a contaminated object, it might activate intrusive thoughts and anxious feelings but those feelings will go away on their own, without washing, if given time). 

Once this new learning and related new expectations are sufficiently reinforced (via repeated ERP exercises), Foa and Kozak suggested that the underlying fear structure goes through a transformation. Within this transformation, the fear structure changes from something like:

“Contamination is dangerous because it will activate intrusive thoughts and anxious feelings that last forever unless I decontaminate.” 

To:

“Contamination is safe because any activation of intrusive thoughts and anxious feelings will be momentary and will go away all on their own.” 

This change in the underlying fear structure, they thought, is the underlying mechanism which facilitates symptom reduction and successful treatment of OCD. And so, Foa and Kozak suggested that the key signs of successful emotional processing in exposure treatment are:

1. Activation of the fear structure, including reports from the individual that they’re afraid as well as physiological activation

2. Habituation within session during the exposure, including reports from the individual that they’re less afraid as well as decreased physiological activation

3. Habituation across sessions (e.g., subsequent exposures activate less fear).
   

As you can see in “2” above, they argued that exposures needed to last long enough to achieve habituation. What this means is that the original description of the emotional processing mechanism of ERP treatment suggests that habituation is not only nice to have but that it’s a general requirement of effective exposure and response prevention therapy. 

It’s this sort of conceptualization that, I think, frequently leads professionals to describe ERP to their clients in language like “face your fear until it doesn’t scare you anymore” and “stay in the exposure until your anxiety goes away”.

Although habituation is an important part of ERP treatment, it’s not true that successful ERP treatment requires clients to habituate during an exposure. In fact, emphasizing that habituation is the sign of a successful exposure is not only untrue but potentially harmful, as it can reinforce the idea that anxiety is bad and in treatment we’re eagerly waiting for it to go away.

In Part 2 of our series Habituation: Always appreciated, never expected, we’ll review how come I say that habituation is not a requirement of successful ERP treatment, including a review challenges faced by the original emotional processing model, new lessons we learned as a result of these challenges, and what this means for effective ERP treatment.

References

1. Foa, E. B., & McLean, C. P. (2016). The efficacy of exposure therapy for anxiety-related disorders and its underlying mechanisms: The case of OCD and PTSD. Annual Review of Clinical Psychology, 12(1), 1-28.

2. Meyer, V. (1966). Modification of expectations in cases with obsessional rituals. Behaviour Research and Therapy, 4(4), 273-280.

3. Rachman S., Hodgson R., Marks I.M. (1971). The treatment of chronic obsessive-compulsive neurosis. Behaviour Research and Therapy 9(3), 237–47.

   Meyer, V., & Levy, R. (1973). Modification of behavior in obsessive-compulsive disorders. In H. E. Adams & P. Unikel (Eds.), Issues and Trends in Behavior Therapy (pp. 77–137). Springfield, IL: Charles C. Thomas.

   Marks I.M., Hodgson R., Rachman S. (1975). Treatment of chronic obsessive-compulsive neurosis by in-vivo exposure. A two-year follow-up and issues in treatment. British Journal of Psychiatry 127, 349–64.

4. Foa, E. B., & Kozak, M. J. (1986). Emotional processing of fear: exposure to corrective information. Psychological Bulletin, 99(1), 20-35.