Keywords

As reviewed elsewhere in this book, the line between these three waves is difficult to draw (see earlier chapters of this volume). Arguably, this line is even harder to draw for the treatment of anxiety disorders, OCD, and OCRDs because the behavioral principles of habituation to bodily states (e.g., anxiety, fear) and extinction of avoidance responses are an important aspect of the treatment across all three waves (Twohig et al., 2013). This commonality is seen in the centrality of exposure exercises to all three waves, although the proposed process of change in each one of these phases varies (Twohig et al., 2015). Still, we believe it would be remiss to write that these three waves did not occur in the treatment of anxiety, OCD, and OCRDs. We will argue that there have been slow but notable refinements in behavior therapy’s conceptualization of anxiety disorders, as well as notable modifications to treatments within each wave.

While each treatment that falls under the “third wave” category differs, the following are a set of key features that may distinguish this third wave from the first and second, especially as the third wave applies to anxiety disorders. First, while many of the third wave therapies have a focus on symptom reduction, they also have a strong focus on increased general functioning. Some could argue that symptom reduction obviously leads to increased functioning. While that view is reasonable, the focus on symptoms versus functioning will alter the measures used in therapy, determining when the client reaches the end of therapy, and how sessions are structured. As a simple example, a therapist who is focused on symptom reduction might track levels of anxiety and avoidance per week, whereas a third wave therapist might choose to ask about increases in the frequency of engaging in meaningful activities instead.

A second broad difference is a focus on first versus second order change of internal experiences—in other words, whether the therapy aims to change the target private event or instead alter how the client responds to them. A very simple example is the use of subjective units of distress (SUDS) in many exposure therapies. To those who have done traditional exposure therapy (e.g., Foa et al., 2012), the main goal is to see within and between session decreases in SUDS. In many of the third wave therapies, the focus is on metacognition, mindfulness, and acceptance of the internal experience. We do not seek to increase or decrease any internal experience per se, but to alter its effect on behavior. For example, in traditional ERP, the aim is to decrease OCD symptoms (i.e., obsessions and compulsions) while in ACT, the aim would be to increase valued behaviors that OCD symptoms may interfere with.

Additionally, there are a number of procedures that are more central to the third wave of therapies for anxiety. Emotional acceptance or tolerance has found its way into the vernacular of most therapies for anxiety disorders (e.g., Abramowitz & Arch, 2014). Still, emotional acceptance and tolerance are central to most third wave therapies and are seen as the end outcome and not a step toward habituation as typically described by second wave cognitive behavioral treatments for anxiety (Arch & Craske, 2008). A second notable procedural difference is cognitive challenging as compared to stepping back from thinking. This difference is very consistent with the concept of first vs second order change (i.e., change the content versus change the function). In much of the work we will describe here, third wave approaches will use strategies to step back from and/or instruct the client to simply notice inner experiences. Most third wave therapies will aim to help the client take a metacognitive stance (i.e., thinking about thinking) toward their obsessions, fears, or anxieties versus actively engaging with them. Third, the concept of being present and mindful is central, or at least a notable part, of most of these third wave therapies. As a way to challenge the power of anxiety or fear-provoking stimuli (that occasion avoidance and meaningless action), a third wave therapist may help the client to mindfully notice all the stimuli in the environment—including the other private thoughts and emotions. Mindfully noticing may be defined as nonjudgmental awareness of internal experiences without trying to remove or change them and can be measured through a variety of questionnaires or through personal observations of behavior (e.g., noticing that avoidance is not chosen). This approach can open the response options to all stimuli available instead of the few that are triggering (e.g., the Choice Point exercise; Harris, 2019); in other words, the client is made aware of potential actions beyond avoidance. Several third wave therapies thereby have a strong focus on valued action over actions that are about emotional avoidance. For example, choosing to visit a family member with a dog instead of asking the person to meet at a restaurant in order to avoid the feared dog. We would hope for a client to shift their daily behaviors from regulating inner experiences to living a meaningful life.

Overview of Exposure Therapy in the Third Wave

These distinctions all play into the concept of exposure therapy in a meaningful way. Exposure therapy in third wave therapies is still the core of useful treatment for almost all anxiety, OCD, and OCRDs (e.g., Twohig et al., 2015). In Foa and Kozak’s (1986) seminal paper on traditional exposure therapy, the authors discuss emotional processing theory and the idea that a cognitive “fear structure” is activated when confronting a feared stimulus, leading to typical responses such as escape or avoidance. Their theory suggests that exposure exercises bring on this cognitive and behavioral fear response, but if the client does not engage in escape or avoidance then the avoidance response will habituate to the feared stimulus and in addition they will gain have corrective knowledge (e.g., the feared outcome does not occur, the anxiety/fear is tolerable). Within and between session habituation is a key indicator of this process. However, after many years of research, we have found that within and between session habituation is not related at all or notably related to improvements in anxiety disorders (Asnaani et al., 2016).

Interestingly, while traditional exposure therapy was largely based on operant and classical research on learning and extinction (Mowrer, 1960), basic behavioral research since then has shown us that any learned response cannot be unlearned (Bouton et al., 2001). Basic behavioral principles on extinction show that it just takes the right context for a response to re-occur: spontaneous recovery (through passage of time), disinhibition (through renewed responding to a novel stimulus), reinstatement (through presentation of an unconditioned stimulus or reinforcer), renewal (through change in context), or resurgence (through a new behavior introduced during extinction). The difficulty in completely stopping a fear or anxiety response from continuing to occur has been written about by leaders in the treatment of anxiety disorders (Bouton et al., 2001).

Relatedly, behavioral research on language and cognition has found the same parameters with extinction to cognitive responses, where once a cognitive response is trained it simply takes the right context to bring it back (Wilson & Hayes, 1996). Recent research has found that the same is true with avoidance responding conditioned through stimulus equivalence or relational responding (Dymond et al., 2018). Thus, it is not just the traditional fear or anxiety response that is difficult to unlearn, but all cognitive activity surrounding the fear response and associated behavioral avoidance.

This all flows logically into the most supported cognitive behavioral understanding of exposure therapy to date: inhibitory learning (Craske et al., 2014b). In inhibitory learning, the link between the unconditioned response and the conditioned response is never unlearned. Even if habituation occurs, the right context will bring that response back. Instead, there is competing learning with the original learning, inhibiting the initial fear response and associated avoidance. Thus, a key feature of inhibitory learning are exposure exercises that focus on building “tolerance” to anxiety and fear throughout the course of treatment.

To us, this is a notable step towards a second order approach (altering function) to the treatment of inner experiences in anxiety, OCD, OCRDs. Exposure exercises from the third wave approach are therefore not about habituating to internal experiences—they are chances to practice being mindful and creating distance from thoughts so that this is easier to do in important extra-therapy situations (Twohig et al., 2015). For example, in acceptance and commitment therapy (ACT) we might approach a stimulus and stay in contact with it while it provokes emotion, but the function is to practice feeling rather than waiting until it decreases. Instead of focusing on therapy techniques that will result in a first order reduction in a cognitive or physiological response, acceptance and mindfulness procedures seek to promote stepping back from and just noticing the occurrence anxiety or fear. Therefore, we look at exposure exercises more so as an opportunity to see inner experiences for what they are (just thoughts, feelings, and sensations) and as chances to practice living meaningful lives and moving towards values. We seek to teach the client how to live with those behavioral and emotional responses and not be affected by them. Similar to a tolerance model, we seek to teach acceptance as a lifelong approach to internal experiences, rather than tolerate the moment to a future that has less difficulty.

Research Overview

A formal vote regarding who wants their treatment to be considered part of the third wave of behavior therapy never occurred; relatedly, we were not unanimous on using the terms “first, second, or third wave.” Nonetheless, following the previous guidelines on elements that are consistent with third wave therapies we are choosing to review: mindfulness-based therapies (MBT; mindfulness-based stress reduction [MBSR] and mindfulness based cognitive therapy [MBCT], Dialectical Behavior Therapy [DBT], and ACT).

Mindfulness Based Therapies for Adult Anxiety Disorders

While MBCT and MBSR are different treatments, to be consistent with most large meta-analyses, we will combine them in our review. As is well-known, MBSR was largely developed for chronic medical conditions (Kabat-Zinn, 2003) and MBCT was mostly focused on reducing relapse in depression (Kuyken et al., 2008). Both therapies include mindfulness practice with the hope of providing clients with skills to effectively respond to their distressing internal experiences. Specifically, in the treatment of anxiety, mindfulness is used to help the client be aware of all bodily states and take an open and accepting stance towards those experiences. This process could combat ruminations or worry, common themes in anxiety disorders (Kabat-Zinn, 2003; Mathews, 1990). In addition, several authors have proposed the varied function mindfulness plays in the reduction of symptom related distress; for example, the cognitive shift to a non-judgmental perspective towards thoughts (Kabat-Zinn, 1982) or mindful exposure to distressing states may provide healthy alternatives to worry (Hayes, 2002).

As reviewed in the following meta-analyses, there are randomized controlled trials (RCTs) for heterogeneous anxiety problems: social anxiety disorder, generalized anxiety disorder, posttraumatic stress disorder, panic disorder, and health anxiety. The largest meta-analysis of mindfulness for anxiety disorders to date reported a within condition (pre-post) Hedges’ g of 0.63 for mindfulness in participants who were not seeking services for anxiety disorders (e.g., seeking services for a different issue but had high anxiety scores), and a Hedges’ g of 0.97 on anxiety in those seeking treatment for anxiety disorders (Hofmann et al., 2010). These results indicate that there is moderate support for the use of MBTs as treatments for anxiety disorders. The same team found MBTs had a medium effect size when compared to waitlist, a small effect size compared to active treatment comparisons, but these were not more effective than traditional CBT or behavioral therapies (Khoury et al., 2013).

Another notable meta-analysis analyzed MBTs for anxiety and stress across 47 studies (Goyal et al., 2014). While their review included MBTs and transcendental meditation programs, the results demonstrated moderate between-group effect sizes for anxiety. However, another meta-analysis found that MBT for anxiety disorders was effective when compared to a waitlist condition, but not more effective than another active or evidence-based treatment, such as cognitive behavioral therapy, as recommended by the American Psychological Association (Goldberg et al., 2018). Overall, these results indicate that MBTs are useful, but have not been shown to be more useful than existing treatments for anxiety disorders. Also, these more general meta-analyses found that MBTs have some of their strongest outcomes with anxiety (Goldberg et al., 2018; Goyal et al., 2014).

Dialectical Behavior Therapy for Adult Anxiety Disorders

Evolved from cognitive behavioral therapy (CBT) and composed of individual sessions, phone consultation, and weekly group skills training, DBT was originally developed as a treatment for borderline personality disorder (Linehan, 1993). Among the skills taught in the weekly group trainings are mindfulness, distress tolerance, emotion regulation, and interpersonal effectiveness.

DBT has been shown to reduce anxiety in heterogeneous clinical samples of an intensive outpatient program (e.g., Lothes II et al., 2016). Another mixed clinical sample of undergraduates reported reductions in general and specific anxiety disorder symptoms (e.g., OCD, specific phobia) following an adapted DBT treatment protocol (Panepinto et al., 2015). DBT has also been investigated as a specific treatment adjunct for anxiety. Residential DBT for posttraumatic stress disorder (DBT-PTSD) demonstrated promising results as a treatment for PTSD associated with childhood sexual abuse in two studies (Bohus et al., 2013; Steil et al., 2018). Researchers have also investigated a skills-only intervention for test anxiety, noting reduced symptoms of test anxiety after receiving only mindfulness DBT skills (Lothes II & Mochrie, 2017) and reduced overall anxiety using DBT as a whole (Neacsiu et al., 2014). On the whole, DBT shows some feasibility as a treatment for anxiety, even when treatment has been slightly remodeled from the original format.

Acceptance and Commitment Therapy for Adult Anxiety Disorders

ACT aims to increase psychological flexibility, the ability to live in the present moment, regardless of distress, while engaging in behavior based on one’s values. To date there has been one meta-analysis showing small to large correlations between psychological inflexibility and different forms of anxiety (Bluett et al., 2014).

There is a wide range of evidence supporting ACT as a treatment for mixed anxiety disorders in a diverse set of delivery methods (e.g., individual, group, bibliotherapy, web-based) and settings (e.g., outpatient, college, residential; Gloster et al., 2020). In a recent a meta-analysis of ACT meta-analyses, 6 of 7 meta-analyses reported small to medium between condition effect sizes for ACT as a treatment for anxiety; the remaining one favored active control conditions with a negligible nonsignificant effect size (Gloster et al., 2020). As covered in several other meta-analyses (Bluett et al., 2014) and systematic reviews of ACT for anxiety disorders (Twohig & Levin, 2017), multiple RCTs have been completed for every anxiety disorder. Across all meta-analyses the effect size was at least medium in favor of ACT. Most notably, ACT performed better than other active control conditions, but only equivalent to CBT.

Mindfulness Based Therapies for Anxiety Disorders in Youth

A recent meta-analysis found five RCTs comparing MBTs to a control condition (e.g., waitlist, narrative exposure therapy) for youth (Borquist-Conlon et al., 2019). One study used ACT and the remaining four were not traditional MBT but were manualized mindfulness-oriented treatments. The investigators found a medium effect size (Hedges’ g = 0.62) on anxiety measures. When excluding ACT and DBT, another meta-analysis found mindfulness-based interventions to be efficacious for treating anxiety in youth (Kallapiran et al., 2015). They analyzed 11 randomized trials of MBSR and MBCT, finding large effect sizes when compared against nonactive treatments. Thus, there is limited support for MBCT and MBSR for youth with anxiety disorders as RCTs are mostly limited to nonactive controls.

Dialectical Behavior Therapy for Anxiety Disorders in Youth

In a meta-analysis of DBT-Adolescent, the authors analyzed three randomized controlled trials with a total of 146 participants with heterogenous diagnoses (Hunnicutt Hollenbaugh & Lenz, 2018). Each study showed a small to medium between-conditions effect size favoring DBT-A as compared to TAU or multimodal therapy. The overall effect size for DBT-A for anxiety was .47.

Acceptance and Commitment Therapy for Anxiety Disorders in Youth

ACT for youth has not been thoroughly investigated as it has for adults. In a review from 2015, there were ACT outcome studies with positive results for children or adolescents who were diagnosed with OCD, learning disability and anxiety, and posttraumatic stress disorder (Swain et al., 2015). A recent meta-analysis of 14 RCTs (N = 1189) of ACT for youth combined outcomes across depression, anxiety, and problem behavior (Fang & Ding, 2020). Much like the adult data, ACT showed medium to large effect sizes against treatment as usual and waitlist, but there was no significant difference from traditional CBT. When analyzing depression and anxiety alone, the same outcomes were found.

Mindfulness Based Therapies for OCD and OCRDs in Adults

Mindfulness is thought to be helpful with avoidance of and/or rigidity towards internal experiences (including reassurance-seeking or rituals), interrupting internal OCD processes (e.g., mental rituals), and attentional biases common in OCD (Didonna, 2009). Indeed, individuals diagnosed with OCD report lower mindfulness qualities (e.g. nonjudgmentalness, awareness) as compared to a nonclinical group (Didonna, 2009). Mindfulness has demonstrated potential as a way to cope with difficult obsessions (Fairfax, 2008).

Studies looking at more structured mindfulness treatments (e.g., MBSR or MBCT) found promising results. One multiple baseline study found that MBCT reduced OCD, depression, and anxiety symptoms (Liu et al., 2011). The use of MBCT was also supported by a recent pilot trial looking at the effectiveness of group MBCT for OCD; results indicated significantly decreased OCD and increased mindfulness abilities (Didonna et al., 2019). Larger RCTs of mindfulness treatments for OCD show inconsistent findings. One study found that biweekly MBCT for “pure O” OCD left 67% of participants in remission, as determined by a 55% reduction in Yale Brown Obsessive Compulsive Scale (YBOCS) scores (Kumar et al., 2016). On the other hand, mindfulness-based exposure and response prevention (ERP) did not differ from ERP-only outcomes, beyond increased levels of mindfulness (Strauss et al., 2018).Several RCTs have reported that MBCT following CBT in patients with lingering OCD symptoms ultimately reduced OCD, anxiety, and depressive symptoms while increasing mindfulness and self-compassion (Key et al., 2017). However, no differences in OCD symptoms were found following MBCT or psychoeducation groups after receiving a full course of CBT (Külz et al., 2019). The data on mindfulness for OCRDs are limited, with only one pilot study demonstrating improvements in tic-related symptoms after MBSR (Reese et al., 2015).

Dialectical Behavior Therapy for OCD and OCRDs in Adults

There is some evidence that patients with OCD have difficulty identifying and regulating a variety of emotions (Stern et al., 2014). However, there is only one published study looking at DBT as a treatment for OCD. Ahovan et al. (2016) assessed the effectiveness of eight, 90-min DBT sessions covering all four DBT modules for OCD resulting in reduced OCD severity and increased emotion regulation as compared to a control group.

Some theories suggest that hair pulling is utilized as an emotion regulation tool, particularly in response to negative emotions, thoughts, or urges (MacPherson et al., 2013). The focus of this research illustrates that, if hair pulling is functioning as an emotion regulation strategy, then DBT combined with habit reversal training (HRT) may provide the best outcomes over other treatments (Welch & Kim, 2012). DBT, as compared to a control group, resulted in greater improvement in hair pulling symptoms and emotion regulation difficulties (Keuthen et al., 2012). Hair pulling severity was reduced and gains were maintained at follow-up (Keuthen & Sprich, 2012).

Acceptance and Commitment Therapy for OCD and OCRDs in Adults

The amount of research on ACT for OCD is quite substantial (Bluett et al., 2014). In addition to many single subject designs on ACT for OCD, there have been at least six RCTs on ACT for OCD with two completed in the USA and the remaining in Iran. ACT outperformed progressive relaxation training in 79 adults with OCD showing response rates of 55–65% compared to 13–18% at post-treatment and 3-month follow-up (Twohig et al., 2010). In a follow-up to that study, ACT was combined with traditional ERP and compared to traditional ERP alone (Twohig et al., 2018). Treatments were equivalent and successful with response rates of 70% for ACT+ ERP and 68% of ERP at posttreatment, and 60% and 64% at follow-up. In the four trials of ACT for OCD in Iran, all followed the same brief protocol used in Twohig et al. (2010) that does not emphasize exposure exercises. Consistent with Iranian medical system and culture, participants were often on stable doses of SSRIs and group therapy was often female only. Pretreatment YBOCS scores were in the 22–28 range, posttreatment was in the 13–17 range, and follow-up was in 6–15 range. ACT was always found to be superior to waitlist and never stronger than traditional CBT, although multiple trials found process of change differences between the treatments with psychological flexibility being involved in ACT more so than SSRIs alone (Baghooli et al., 2014; Esfahani et al., 2015; Rohani et al., 2018; Vakili et al., 2015).

In addition to multiple single subject studies and one open trial on ACT alone or ACT+HRT for adult trichotillomania (Haaland et al., 2017; Twohig & Woods, 2004), three randomized trials have tested ACT or ACT+HRT for adults with trichotillomania. In a RCT examining ACT enhanced HRT as compared to waitlist, the ACT condition had a 66% response rate compared to 8% of the waitlist (Woods et al., 2006). The same ACT+HRT protocol was tested when delivered over teletherapy, with similar results; 58% responders in the treatment group compared to 17.7% in the waitlist (Lee et al., 2018). Finally, ACT alone was tested as treatment for trichotillomania in adults and adolescents as compared to a waitlist; results supported the use of ACT alone for trichotillomania (Lee et al., 2020). The treatment group showed a 77% decrease in pulling versus a 10% decrease in the waitlist. In addition to hair pulling, one multiple baseline testing ACT for skin picking found four out of five participants reporting reduced skin picking at posttreatment, as well as increased psychological flexibility (Twohig et al., 2006). However, only one participant maintained these gains at follow-up.

Third Wave Therapies for Youth with OCD and OCRDs

Few studies have found evidence supporting the use of mindfulness and acceptance-based treatments in youth and teens with OCD and related disorders. In a multiple baseline for ACT for OCD in adolescents, 44% reported a decrease in symptoms (using the CYBOCS) at follow-up (Armstrong et al., 2013). In another study, adolescents with OCD already taking SSRIs were randomly assigned to group ACT, group CBT, or SSRI alone (Shabani et al., 2019). Both ACT and CBT groups had significant reductions in OCD severity at post and follow-up (Shabani et al., 2019). Lastly, one study of tic disorders in adolescents found no differences between ACT enhanced HRT as compared to ACT alone (Franklin et al., 2011).

Thoughts on the Three Waves

At an outcome level, third wave therapies do not appear to be more beneficial than first or second wave treatments for anxiety disorders and OCD (Bluett et al., 2014). Interestingly, researchers have not found benefits for the second wave over the third in terms of outcomes for these disorders, especially since exposure-based therapies are one of the most beneficial treatments for anxiety (Tolin, 2009). Again, no matter how exposures are done in the trials, we have not greatly increased its effectiveness (Tolin, 2009). The data on OCRDs are a little different because the work is much less advanced than with anxiety and OCD. A small amount of work was conducted during the first phase of behavior therapy (Azrin & Nunn, 1973) and even less for second wave procedures for trichotillomania and skin picking. A moderate amount of work has occurred testing a traditional CBT procedure for body dysmorphic disorder (BDD) showing large effect sizes for CBT over waitlist or credible placebo controls (Harrison et al., 2016). There has been a fairly steady stream of work on ACT and DBT for trichotillomania and skin picking (Bluett et al., 2014).

One thing that stands out regarding the third wave work on anxiety disorders and OCD is that the sample sizes of the studies are often fairly small and very few are federally funded. While there is not an exact date for when the third wave started, we can generally say around 2000. At that time, there was a notable shift in the funding priorities of the National Institute of Health (NIH) away from general efficacy trials for diagnosable mental disorders (Wilson, 2022). The real bulk of the efficacy work occurred in the 1980s and 1990s, when traditional CBT was developed for most anxiety disorders and OCD. The efficacy rates of CBT for anxiety disorders and OCD are high enough—around 50% response rate (Loerinc et al., 2015)—that NIH shifted priorities away from RCTs and towards neurobiological understanding of psychopathology (Goldfried, 2016). Thus, much of the third wave missed the opportunity to do the larger well-controlled RCTs supported by federal funding. Nowadays, most of the large funding for third wave research is in medical conditions or substance use (e.g., Vilardaga et al., 2020)

Process of Change Research

One notable shift that occurred from the first to third wave was an increased focus on processes of change and moderators (Hofmann & Hayes, 2019). We do not think that the third wave therapies deserve the credit for helping shift a focus to why treatments work and for whom. That was likely a natural progression in psychotherapy over time. First wave therapies for anxiety were largely based off traditional behavioral principles. With time, these procedures developed a more cognitive orientation. They shifted from focusing on extinction and habituation to elements of cognitive change (Foa & Kozak, 1986). Many of the second wave protocols for anxiety were more logical than process of change focused. For example, Barlow’s work on panic disorder cut down a larger treatment package to focus on the elements that were most helpful by excluding muscle relaxation (Pompoli et al., 2018). However, the steps to engage in that dismantling were less process based and more technique based.

More recently, a large focus has shifted to the processes that underlie disorders and processes and techniques that can successfully alter those processes (Hofmann & Hayes, 2019). Even more so with more modern statistical methods, we can track temporality of when a process change occurs and how that affects overt actions. Relatedly, we are finding through single and multiple mediation studies that one process of change can affect another in a useful way, such that a decrease in a potential mediator occurs with the support of another mediator (e.g. Ong et al., 2020; Arch et al., 2012; Wolitzky-Taylor et al., 2012). For example, in a larger trial (N = 120 adults with an anxiety disorder) comparing ACT to traditional CBT, both groups showed strong improvements at posttreatment, but ACT showed stronger improvements at follow-up. While there were greater improvements in psychological flexibility in the ACT condition at follow-up, second wave CBT showed better quality of life. In a secondary mediation analyses, changes in cognitive defusion were stronger in ACT, but cognitive defusion predicted worry reductions in CBT over ACT (Arch et al., 2012). In moderation analyses conducted on this trial, CBT was more effective for those with moderate anxiety sensitivity and no comorbid condition whereas ACT was more effective for those with comorbid mood conditions (Wolitzky-Taylor et al., 2012). Finally, they investigated physiological and behavioral moderators of treatment outcome (Davies et al., 2015), finding that ACT did better than CBT for those with high behavioral avoidance. Thus, these overall results show that ACT and CBT are both effective treatments, one may show stronger follow-up, some treatment matching can occur, and they are associated with different processes of change.

Another larger RCT (N = 87 adults with social anxiety disorder) compared ACT, CBT, and a waitlist (Craske et al., 2014a), finding that ACT and CBT outperformed the waitlist, with no differences between ACT and CBT. Lower psychological flexibility was associated with better outcomes in CBT at follow-up. Low and high fear of negative evaluation was also associated with better outcomes in CBT over ACT. In terms of mediators, ACT showed steeper initial declines in session-by-session negative cognitions and psychological flexibility, whereas CBT showed steeper declines towards the end of treatment (Niles et al., 2014). Psychological flexibility also predicted outcomes in ACT but not CBT. In this study no outcome differences were found, but some process and moderator differences were noted.

Finally, secondary analyses from a recent multisite RCT comparing ACT-based ERP to traditional ERP in 58 adults with OCD (Twohig et al., 2018; reviewed in the ACT for OCD and OCRDs in Adults section) found sudden gains occurred in 27% of the sample and were most common in contamination OCD (Buchholz et al., 2019). While sudden gains were not associated with changes in cognitive distortions or psychological flexibility, there were only 2 (6%) participants with sudden gains in the ACT+ERP condition as compared to 10 (35%) in the ERP condition. Relatedly, we also found that cognitive fusion predicted the symmetry-related OCD symptoms beyond obsessive beliefs, suggesting that addressing obsessive beliefs versus buying into thoughts might be moderated by OCD type (Hellberg et al., 2020). Again, looking at the entire sample, we found that those with less dysfunctional appraisals did better in ERP over ACT+ERP (Ong et al., 2020). At the process of change level, increases in psychological flexibility predicted improvements in both conditions, whereas change in dysfunctional appraisals was only relevant in ERP. Finally, in a review of video recorded therapy sessions, our team found that the number one predictor of outcomes—beyond minutes of exposure exercises—was experiential delivery of an acceptance/tolerance rationale (Ong et al., 2022). While these are results of just one RCT, it is visible that it is more complicated than the similar outcomes of ERP and ACT+ERP. Elements from each intervention were predictive at a moderating and mediating level.

Therefore, third wave treatments seem to have their place in CBT, not just because they theoretically fit and there is some empirical evidence that their processes of change might be specific to them, but because they might be offering some elements to therapy that had either been minorly present or not present at all in the first two waves. Concepts such as mindfulness, cognitive defusion, and a clear focus on linking treatment goals, values have arguable been built out by the third wave treatments. These methods have been brought into other versions of CBT and are key in process-based approaches to CBT (See chapter “Advantages of Third Wave Behavior Therapies” of this volume).

Clinical Example Using ACT

We are not going to present a real case, rather we will present information gleaned largely from the following trial comparing ACT+ERP to ERP alone in the treatment of adult OCD (Twohig et al., 2015, 2018). Even though this information is based on ACT many of the general principles would apply across the therapies reviewed; and even though it is on OCD, very similar assessment, conceptualization, and treatment strategies would apply.

When conducting assessment from a third wave point of view, we would want to assess OCD severity. It is worth noting that assessment of OCD severity from a second order change standpoint can have complications. Specifically, outcome measures usually have questions on the severity and frequency of internal experiences such as obsessions, along with content area (e.g., fears about germs, violent intrusive thoughts). For example, the YBOCS asks about frequency of obsessions and compulsions. These types of questions can confuse the client and assessor alike because we might literally work with the client on the idea that obsessions cannot be controlled. Therefore, assessment should also include measure on quality of life and general functioning, such as the Quality of Life Scale (Burckhardt & Anderson, 2003), the Mental Health Continuum short form (Lamers et al., 2011) or the Work and Social Adjustment Scale (Mundt et al., 2002). Questionnaires on daily functioning seem to work better than global quality of life measures because lager quality of life issues (e.g., work, relationships) can be slow to change, but smaller daily functioning issues can change quickly.

Of course, it is important to assess process of change constructs that are consistent with the treatment model one is working from. There are standard measures of psychological flexibility (e.g., Acceptance and Action Questionnaire II; Bond et al., 2011) and disorder specific assessments of psychological flexibility exist for OCD, trichotillomania, and hoarding disorder are available: AAQ for Obsessions and Compulsions (AAQ-OC), AAQ for trichotillomania (AAQ-TTM), AAQ for hoarding (AAQ-H; Ong et al., 2019). Finally, in addition to the larger battery of assessments given at the beginning of treatment, after treatment, and at reasonable intervals throughout treatment, we suggest self-monitoring of a clear overt action (e.g., compulsions). This monitoring allows for day to day tracking of treatment progress.

In terms of case conceptualization, we look at disorder severity data and other standardized assessments of important psychological processes (e.g., psychological inflexibility around obsessions). Those assessments can provide us with a nomothetic view of the clinical presentation. For idiographic information, the ACT Advisor, a short questionnaire, provides a form with scales for the six processes of change that are addressed in ACT (i.e., acceptance, cognitive defusion, self-as-context, present moment awareness, values, committed action). This assessment allows us to determine where the client is on the six processes we will address in therapy. For example, if a client with OCD is low on present moment awareness, we would expect them to have trouble staying mindful, often thinking about the past/future or about their current obsession (e.g., Thoughts during a dinner party such as “Is this table clean enough?” or “Are there germs on this knife?”, rather than paying attention to their meal and company), and have general difficulty flexibly using their attention. Alternatively, a client who scores high on present moment awareness may easily stay in the present moment and direct their attention to what is most important to them in that moment (e.g., noticing the mind’s concern about cleanliness and choosing to pay attention to the dinner party instead). Thus, low scores often indicate greater psychological inflexibility (e.g., fusion). We find that clients are either low on all six processes, or they are low on the more “acceptance and mindfulness” processes but high on the values and behavior change processes. We often find that there is a notable subset of those with OCD who are “white knuckling” through their disorder. For example, a person with obsessions around driving (e.g., fears about hitting someone) may be able to drive, but only enduring shorter distances with great difficulty and reliance on compulsive behaviors (e.g., checking their rearview mirror to see if they hit a person). Someone who knows what they want and has been trying to do it—although in a nonfunctional way—is in a different spot than someone who is cognitively fused and not having success in pushing through the OCD either (e.g., a person who completely refuses to drive due to intrusive thoughts around driving). We complete the ACT Advisor, or something similar, at most sessions.

In terms of actual therapy, the main focus is to teach the client how to be psychologically flexible around their obsessions by utilizing and engaging them with the six ACT processes. Once the client begins to score on the higher end of the ACT Advisor, we then move into ACT-based exposure exercises (e.g., engaging in activities that provoke anxiety/fear and are meaningful) as an opportunity to (1) pursue their values, and (2) practice interacting with their obsessions in a new, more functional way. The amount of time in therapy needed to develop psychological flexibility is hard to predict. Thus, spend as much or as little time needed to get to that place and keep the appropriate cut-off scores in mind (e.g., below 24–28 on the AAQ-II; Bond et al., 2011). We have seen it as fast as the first session (if the client has experience with these topics) or as long as maybe eight sessions. To teach psychological flexibility, we spend time with the client discussing whether attempts to regulate or control obsessions (e.g., compulsions like hand-washing, mental rituals, self-talk, medication) increase its power or decrease it. We use examples from their own lives where attempts to control, suppress, or otherwise regulate things has actually backfired. For example, a client with trichotillomania may pull their hair in order to satisfy an urge for symmetry in their eyebrows—not only does the urge return repeatedly despite these efforts, but the pulling also results in bald spots.

We then use acceptance, defusion, and mindfulness strategies to help the client see their obsessions for what they are—thoughts, images, and feelings. An example of a common acceptance and defusion strategy used in the treatment of anxiety and OCRDs is the “tug of war with a monster” metaphor. Clients are asked to consider their obsessions as a monster they are currently playing tug of war with. Whenever the monster calls out to them (e.g., what if I did something sacrilegious?), clients often pick up the rope and fight or bargain with the monster (e.g., praying excessively, re-assuring oneself that it was not a sin). We would instead encourage the client to drop the rope and continue about their lives—sometimes the monster will call out to them and they do not have to respond or pick up the rope.

“The movie theater” exercise utilizes mindfulness and defusion to aid clients in viewing obsessions for what they are. In this exercise, clients are guided through a visualization where they imagine themselves entering a movie theater with a blank screen. Clients imagine themselves sitting in the audience and then view their thoughts as passing images or words on the screen. In this way, clients practice that they are not their urges or obsessions, but an observer of each thought or feeling as it passes by. After seeing the obsession (e.g., I fear I might harm my child), they can choose to observe it and not respond.

In sum, we are aiding the client to understand that obsessions are about events but are not the events themselves. For example, a client who has an obsession about sexually abusing their child would work towards an understanding that having these thoughts is not the same as engaging in the feared behavior. One way to illustrate this concept is to have the client pretend to bite into a half a lemon and imagine the reaction their body has. We might then compare that reaction to the one the client has when they picture their obsession. It can be a strong reaction, but it is a thought about a thing, not that thing (e.g., a thought about sickness, not actually sickness). The difference is really important—we may want to avoid the real thing, but we do not have to avoid thoughts about something if it is not functional.

We also bring in values discussions early on in therapy. Therapy is never primarily about OCD reduction but about moving toward valued goals in life. It is always about building relationships, growing in work or school, or whatever else they care about. We link the distress obsessions bring on as an indicator that something important is happening and then to use that moment as an opportunity to go towards their values. For example, if a client feels fear around harming their child in some way, instead of avoiding that feeling (e.g., refusing to be alone with the child), we aim to approach that feeling in the service of the value of being a parent (e.g., taking time to intentionally be present with the child). Finally, every session has a behavioral commitment to go towards their values in some specific way while practicing psychological flexibility. Again, these exercises are always about building openness to obsessions while pursuing values.

Once psychological flexibility is present, we like to engage in longer in-session exposure exercises and assign larger out of session ones. These exercises follow much of the functional principles that have already been described. Specifically, the exposure exercises are seen as opportunities to follow one’s values and practice developing a new relationship to one’s obsessions—a more psychologically flexible one. Each exposure session begins by asking the client how their exercises (i.e., exposures or behavioral commitments) went from the past week. We are interested in how open they were to the anxiety/obsessions that occurred during those exercises and whether they completely engaged anyway. Based on an assessment (e.g., ACT advisor), we would spend some time building up the needed ACT process of change. Once we felt the client was in touch with that ACT process, we would work with the client to develop an exposure exercise that they thought they could be fully open to for a specific, agreed upon time period. We do not usually build a hierarchy, but if we were to (because it can be wise to have needed stimuli ready) we would base exercises on the client’s willingness to do the exercise instead of how much distress it would cause.

Staring the ACT-based exposure involves reminding the client to get in touch with the value they are pursuing and coaching them to engage with the process of change that was discussed earlier in the session. The exposure is seen as an opportunity to interact with their obsession in a different way (e.g., accepting, distanced, defused) while pursuing values. Because it can be hard to see whether the client is practicing defusion or acceptance, we check in and coach the client along during the session. We might ask, “how are you treating the obsession?,” or “how open are you to the obsession right now?,” or “are you connected with why it is worth doing this exercise?” We do not ask for SUDS, but we have asked about “willingness.” We end the exposure when we complete the agreed upon task. Because we are practicing building a new relationship to the obsession, it really does not matter if the obsession or anxiety increases or decreases—we want the way the client relates to that feeling to change. We would plan homework that matches the skills we practiced in session.

Conclusion and Future Directions

Arguably, the discussion about the role of the three waves of therapy in anxiety, OCD, and OCRDs is an example of the discussion of the three waves in general. The first wave of behavior therapy was groundbreaking in its ability to successfully treat disorders that seemed overwhelming at the time. The second wave added a logical and scientific approach to dealing with cognitions. We feel the third wave build upon the previous two by retaining the behavioral thinking of the first wave and the focus on cognition from the second. The third wave takes a different stance towards language and cognition than the second wave. We feel confident it is new. Having strong technologies that can focus on first order change (second wave) and second order change (third wave) of cognitions and other internal experiences is key. Many disorders fall under the anxiety, OCD, and OCRD umbrella, and while they share many functions, they have their own features. In OCD alone, we can have strong fears (e.g., an obsession around killing someone) or a feeling that something is not right, but not dangerous. We have urges that a hair needs to be removed in trichotillomania and a fear of dying in in a panic attack. We need many methods of conceptualization and treatment for the myriad of internal experiences that occur in anxiety, OCD, and OCRDs, to be built within the behavioral theory put forth in the first wave.

This situates the important work of process based cognitive behavioral therapies (PB-CBT) at the forefront. Process based CBT has been proposed within our field for a long time (Hayes et al., 1996), but more formal writing on the topic has increased lately (Hofmann & Hayes, 2019; O’Donohue & Fisher, 2009). At the core of PB-CBT is the notion that while we have a method to categorize disorders (e.g., the DSM, or ICD-10), those methods do not capture the complexity of the individuals we work with. PB-CBT also proposes that there are transdiagnostic psychological processes and certain empirically supported techniques are helpful at addressing those processes to produce good clinical outcomes. Thus, it is possible that the best therapeutic practices are not from any wave of CBT, but from all waves. Each wave of CBT has offered unique and important processes and procedures that likely match with certain clinical presentations. Thus, while it is important to recognize new developments in our field, we should also recognize that we have all been helping understand the treatment of anxiety, OCD, and OCRDs.