Ultimately this is an empirical question. After considering that we can look at the possible advantages in a theoretical sense.

Right now there are a handful of studies that have looked directly and they tend to be medium to small. Only a few are published, and one of these barely mentions outcome because it was a piece on process of change. So we have a long way to go before this question will be answered empirically.

Here are the studies done so far:

Rob Zettle, who trained with Beck, did two very small randomized trials on ACT versus CT for depression – one using individual ACT and CT and the other using ACT and CT group therapy. A larger multi-site randomized trial is underway right now. In his two studies (see the ACT Handout) he found Cohen’s d’s at post between ACT and CT of 1.23 (individually delivered) and .53 (group) and at follow-up of .92 and .75. The N was very small though. The ACT group was only an N of 6 in the individual study and about 10 or so in the group study.

The 4 other studies are brand new and are not published yet. Ann Branstetter did a randomized trial with end stage cancer distress. Ann was trained in traditional CBT and she applied CBT procedures she thought would help (such as cognitive restructuring). There was not follow up because the patients were in end stage cancer but at week 12 ACT had a Cohen’s d of .9 compared to traditional CBT on distress over dying. You can email her for details – she is at Southwest Missouri State University.

Jennifer Block’s dissertation at Albany (she was just hired as a faculty member at LaSalle) compared ACT and CBGT in social phobia and found a Cohen’s d of .45 at post in favor of ACT compared to traditional CBT on the behavioral measure (standing up and speaking).

Carmen Luciano’s team at the University of Almeria just did a smoking trial comparing ACT and a CBT package used by a Spanish cancer society and found a Cohen’s d of .42 at a one year follow up on smoking cessation.

Raimo Lappalainen and his group at the University of Tampere has data in an effectiveness trial comparing ACT and traditional CBT (using CBT methods linked to functional analysis, such as skills training, or exposure) in a training clinic. Beginning student therapists were randomly assigned one ACT and one traditional CBT client (N = 14 each condition). Problems ranged across the usual outpatient spectrum but they were mostly anxiety and depression. On the SCL 90 the post Cohen’s d between ACT and CBT was .62. At follow up the effect was larger. Here is the reference: Lappalainen, R., Lehtonen, T., Skarp, E., Taubert, E., Ojanen, M., & Hayes, S. C. (2007). The impact of CBT and ACT models using psychology trainee therapists: A preliminary controlled effectiveness trial. Behavior Modification, 31, 488-511. By thw ay at the process level there was greater acceptance for ACT patients; great self-confidence for CBT patients. Both correlated with outcomes, but when partial correlations are calculated, only acceptance still relates to outcome. The effect was accidentally not included in the publication but at follow up ACT was now significantly better than CBT in self-confidence.

Evan Foreman and James Herbert reported similar data from their clinic at Drexel University: Forman, E. M., Herbert, J. D., Moitra, E., Yeomans, P. D. & Geller, P. A. (2007). A randomized controlled effectiveness trial of Acceptance and Commitment Therapy and Cognitive Therapy for anxiety and depression. Behavior Modification, 31(6), 772-799. In this study 101 heterogeneous outpatients reporting moderate to severe levels of anxiety or depression were randomly assigned either to traditional CT or to ACT. 23 junior therapists were used. Participants receiving CT and ACT evidenced large and equivalent improvements in depression, anxiety, functioning difficulties, quality of life, life satisfaction and clinician-rated functioning. “Observing” and “describing” one’s experiences mediated outcomes for those in the CT group relative to those in the ACT group, whereas “experiential avoidance,” “acting with awareness” and “acceptance” mediated outcomes for those in the ACT group.

It is also known that ACT methods can empower behavioral methods (which are also part of the ACT model by the way ... so this finding is in essences a confirmation of the model itself). For example, consider this study: Levitt, J. T., Brown, T. A., Orsillo, S. M., & Barlow, D. H. (2004). The effects of acceptance versus suppression of emotion on subjective and psychophysiological response to carbon dioxide challenge in patients with panic disorder. Behavior Therapy, 35, 747-766. In it acceptance methods (drawn directly from the ACT book) did a better job than control strategies in promoting successful exposure to CO2 gas in panic disordered patients.

A similar finding was reported in:

Campbell-Sills, L., Barlow, D. H., Brown, T. A., & Hofmann, S. G. (2006). Effects of suppression and acceptance on emotional responses of individuals with anxiety and mood disorders. Behaviour Research and Therapy, 44, 1251-1263. As with the study above, brief acceptance methods led to lower heart rate during exposure to an aversive film and less negative affect during the post-film recovery period that did control strategies in individuals with anxiety and mood disorders.

So far it looks as though there might be a small advantage for ACT over traditional CBT methods in outcomes; there is a different set of change processes involved, and ACT methods may empower traditional behavioral methods.

Theoretically, the strengths of the ACT model as compared to CBT are these.

1. The model is easily scalable and broadly applicable. If you look at the whole outcome literature done so far (RCTs, controlled time series designs, and case studies) the problems targeted form a pretty broad list: PTSD, panic, depression, racist prejudice, burnout, epilepsy, smoking, OCD, pain, psychosis, cancer, diabetes, multiple sclerosis, sports psychology, attitudes against pharmacotherapy, skin picking, learning new procedures at work, heroin abuse, worksite stress, work innovation, marijuana abuse, and several others.

2. The putative processes of change are well specified with at least marginally adequate measures available in most areas. These change processes are a small set and they do not wildly vary from disorder to disorder.

3. The mediational analyses seem to be working. There are by our count already 16 successful formal mediational analyses published, or completed and coming. So far the data are very supportive. The processes successfully examined so far include acceptance, defusion, values, committed action, and psychological flexibility so most of the key ACT have some data in mediational trials.

4. Specific components seem to be working when inductively tested. There are at least 18 such studies. In every case ACT methods are impactful and work in a way that is theoretically coherent. These include all 6 points of the hexagon model.

5. The basic theory is intricately linked with the technology and itself seems to be working. For example, we are approaching 10 RFT studies linked to the three senses of self in ACT; RFT work on values is coming; and so on.

For those who believe only in RCTs of manuals, much of this answer will be dismissed. But the history of science shows that you cannot create a progressive science using only outcome studies. I (SCH) explained why in The Scientist-Practitioner (Hayes, Barlow, & Nelson-Gray, 1999). In a nutshell, though, it is this: without good theory, the technological development problem is based on common sense categories and it becomes empirically and practically overwhelming.

This should not be heard as “ACT adherents say RCTs are not important.” ACT folks have published nearly 30 RCTs of ACT methods. But they are not enough! Development in the areas of philosophy of science, basic principles, applied theory, specification of processes of change and effectiveness are just as important (and in the long run more important) than efficacy tests of technology.

The scientific game the ACT / RFT / Contextual psychology group is playing is this: to try to create a truly progressive science of psychology that can address the human condition in a more adequate way. Sure that is bold, but why not have bold goals? Is the ACT group willing to stand or fall on RCTs as a measure of success? Ultimately yes. But we want and demand another, even more difficult criteria: seeing a more truly useful psychology emerge as a result. That means concepts, theories, components, basic principles, effectiveness, training, dissemination and so on.

We think it is only fair to insist that ACT be measured against its own very difficult criteria when considering the progress of this effort. For example, examining ACT without examining RFT is like examining a cancer drug without looking at physiology.

Like the hare and the tortoise, ACT is following the slow and steady path. We think traditional CBT hopped ahead into a lay theory of cognition -- which produced quick progress but long term problems. We'd rather take the slow, one step at a time approach of contextual behavioral science. Which one will go farthest? Let's see. Let's be patient and see.

If there is an advantage of the ACT wing of CBT as compared to traditional CBT, this is where you are most likely to see it.

It is an empirical question, as was the previous one.

As for data so far, right now we have two studies showing a smaller effect size for ACT than for a traditional CBT procedure done outside of an ACT model. Zettle, 2003 found a smaller effect for ACT than for systematic desensitization with trait anxiety when treating a relatively minor problem (math anxiety). The effect was the same in the area of math anxiety per se.

The second study is Forman, E. M., Hoffman, K. L., McGrath, K. B., Herbert, J. D., Bradsma, L. L., & Lowe, M. R. (2007). A comparison of acceptance- and control-based strategies for coping with food cravings: An analog study. Behaviour Research and Therapy, 45(10), 2372-2386. They compared ACT to a traditional CBT program for those who were impacted at different levels by food. 98 participants with chocolate cravings were exposed to a well known CBT-based protocol (Kelly Brownell’s LEARN program) and an ACT-based protocol or no instructions and required to carry chocolate with them of for two days. Those highly impacted by food related cues ate less and had fewer cravings in the ACT condition. But those not impacted by food, did worse in the ACT condition than in the CBT condition (and both did worse than doing nothing at all).

It may not make that much sense to use a procedure like ACT with minor problems because the issues it raises are so fundamental. This could be proven wrong with data. But note that in the Zettle study, ACT worked better with highly experientially avoidant subjects than with low avoidant subjects; desensitization did not show that relationship; in the Forman study those with high food impact were helped by ACT but not those with low food impact. It is not a comparison to CBT but another study [Masuda, A., Hayes, S. C., Fletcher, L. B., Seignourel, P. J., Bunting, K., Herbst, S. A., Twohig, M. P., & Lillis, J. (2007). The impact of Acceptance and Commitment Therapy versus education on stigma toward people with psychological disorders. Behaviour Research and Therapy, 45(11), 2764-2772 found that ACT was not better than education in reducing mental health stigma significantly among participants who were relatively flexible and non-avoidant to begin with. For experientially avoidant and inflexible participants, however, ACT was much better.

It seems possible based on this line of reasoning that CBT might actually work better than ACT in more confined and minor areas; in more severe or chronic areas ACT, might work a bit better ... and perhaps all of that because more avoidant and inflexible folks will be more dominant in severe areas. That is not a conclusion -- it is too early to say -- but it is a guess based on a few studies so far. And remember that ACT is part of CBT -- when we say "CBT" here we mean CBT methods placed into the context of a traditional CBT model that basically focuses on the idea that thoughts cause emotions and behavior.

It helps to keep in mind that ACT is a model not just a package. All of the behavioral methods and some of the cognitive ones can easily be put into ACT protocols. They are still ACT when that happens if they fit the model. That is especially true with behavioral methods -- which are a node on that hexagon model of ACT.

But ultimately we will have to show that, for example, exposure from an ACT perspective is better than (or at least works through a different process than) exposure from a traditional CBT perspective. We have a couple of small studies that indicate that might be true (e.g., see Jill Levitt’s dissertation in Behavior Therapy, 2004) but not large RCTs on the question. Some of these are underway right now (such as in Michelle Craske’s lab) so in a few years we will know.

Is there much in traditional CBT that is helpful? Yes, of course, and virtually all of what is known to work at the level of components fits with the ACT model so these procedures can be used from an ACT perspective. The things that contradict an ACT model are not known to work as components, such a cognitive restructuring. But even there you can modify it to be more a matter of cognitive flexiblity.

Is the ACT model a better place to put all of these procedures? Let’s see. The answer will probably not be “yes, always.” Presumably it is more likely to be “sometimes yes, sometimes no.” But both the yes and no answers will move us forward, and that is the whole point, not silly name brand struggles.

Some skeptics have not really read the whole literature and considered it carefully. Let's put these aside -- they are easy to detect and there is little to say about such criticism. What you then have left behind are two types. One are honest critics. These are very valuable and helpful people because they can light the way for additional research and development. The differences with honest critics so far seem to be in these areas.

Breadth of the criteria. The ACT / RFT community gives more weight to a model that is working than to RCTs alone. Mediational analyses, RFT progress, AAQ studies, component studies, experimental psychopathology, the like all weigh in very heavily. It is absolutely fair to let RCTs be the ultimate arbiter but if you pick them off one at a time with methodological worries, and focus only on DSM syndromes one at a time, even at  ~120 RCTs you can see less support than people within the ACT / RFT community might believe is there. Over time, however, if the ACT / RFT community does its job, even that problem will be self-correcting because the development path being following includes randomized controlled trials as a centrally important area -- just not the only area.

The temporal measure of progress. Given the larger purpose of ACT / RFT, this harder set of criteria needs to be considered in terms of how hard the actual task is. The ACT / RFT community wants to be held to a high (amazingly high) standard, but this also means that judgments about accomplishment of such goals have to be made in the context of that stated purpose. This does mean that there is a certain prolonged sense of ambiguity. ACT / RFT research is more than 30 years old and critics can still doubt whether we are actually producing a more progressive psychology. That is fair, but then by the time the ACT / RFT community meets its goals to everyone's satisfaction, most folks in psychology and the behavioral sciences will know it, because these goals are so darned lofty.

Breadth of application. The ACT / RFT community think that the breadth of the model really matters, because the model itself claims to be about a deeper understanding of human cognition. In traditional syndromal treatment studies, the models are often quite narrow and breadth of application is not a fair test so when these folks look at ACT / RFT they don't quite know what to say. APA says we are over the bar only in chronic pain in terms of strong empirical support.  Across the board the progress is more notable and the breadth of application is already pretty amazing but only now are good researchers in specific areas doing a deep dive -- modifying protocols and chasing process of change evidence.  If the program succeeds there will be multiple studies of ACT / RFT applications within specific areas. Right now there are about 10 areas with at least 5 outcome studies, and nearly 20 areas with more that two (see the new book on "The ACT Research Journey" by Hooper and Larsson).

RCTs versus controlled time series designs. ACT comes from behavior analysis. If you eliminate time series designs in favor of only RCTs, the outcome data weaken, evne with nearly 120 RCTs and new RCTs now appearing every 2 weeks on average.

Quality of studies. Many ACT studies are put together by students and young faculty. Quite a number or from the developing world. Only a about 15 RCTs right now are funded. These early studies are often underpowered and the methodological bells and whistles are sometimes not there. Accord to a careful review by A-Tjak et al (in Psychotherapy and Psychosomatics, 2014) this is getting better, and we are starting to see replications with better controls. When you compare ACT to established CBT research from the best labs in the world, you are comparing research programs at two very different stages of development. We shall see what happens over time as funded ACT research becomes more common. However, average quality is a poor measure. A small study from, say, Iran is a wonderful thing to see ... how does any weaknesses pull down the more than 15 studies on ACT published in the Journal of Consulting and Clinical Psychology?  You need to look to see if there are enough well done studies. You need to consider small studies that have specific weaknesses by looking at the whole literature. Knocking studies over one at a time means sturies with any flaws contribute nothing. That is, well, stupid. Average ratings means if you get students, or people without funding, or the developing world excited then you are necessarily weaker. That too is, well, stupid. Look at the whole literature and be responsible. 

Published versus coming. ACT / RFT advocates often know about the data that are coming. We may know the researchers involved and feel that we can make some judgments. If you just look at publications (which an outside critic simply must do in order to be responsible) the picture looks different from the outside than it does from the inside. ACT / RFT research has been going on for 30 years, but it has only been visible for a few years, with the publication of the 1999 book on ACT and the 2001 book on RFT. About 75% of the outcome research is in the last 3 years. If the program is truly progressive, these differences will narrow over time however.  If you want to get the recent meta-analyses and are a member go to the publications area. If you are not, then click here to join!

The reviews by Ost. Lar-Goran has been invited to ACT conferences many times to criticize the work. Some of his criticisms have been very useful. Others come from a different research tradition and don't have much appeal (e.g., the demand to focus only on syndromes; the insistance that only syndromal measure matter in outcomes). The other problem is that his two reviews have data problems. The first one (in 2008) attributed differences in methodological quality between ACT and CBT to the sloppiness of ACT studies. In fact, Brandon Gaudiano showed (see Gaudiano, 2009) that if you more collect data on funding the differences more carefully you see that all of these differences were due to funding. The study by Ost (in 2014) used ratings of methodological quality have not been replicated by others using the same scale (see the A-Tjak study; when Ost's rating were compared to this study on the same studies, Ost's were more against ACT and had an unacceptably low kappa of .35).  The scale itself has several problems in my humble opinion but the A-Tjak study used a team approach for ratings that included ACT critics and ACT researchers, instead of using a single ACT critic and student raters. There were also over 80 factual or interpretive errors made in reading the ACT literature, which weaken the conclusions. A response article has been submitted to BRAT.

Bottom line. We think declaring that something is "evidence based" is a communitarian effort that should have the same open and agreed to standards that are carefully applied to all methods. APA has that ... and ACT is listed as evidence based in several areas. SAMHSA has that and ACT is listed in several areas there too. In the ACBS community we prefer to learn from our critics and keep on pursuing our vision and trying to get better.

Everywhere that cognizing humans go. We want a theory of human behavior that allows us truly to make a difference in our homes, schools, workplace, and clinics. The ACT / RFT community wants it all: a technology that works, a theory that works, basic principles, AND a powerful linkage to our deepest human desires. But we can distinguish aspirations from data – and we have created a culture of openness and self-criticism that seems scientifically healthy. It is often that culture which seems most powerful when people first contact the ACT and RFT community. We are using ACT / RFT to create an ACT / RFT community that is open, non-hierarchical, diverse, committed, sharing, caring, and just plain fun. The vitality the young professionals and students as seen on this very website beg for the question: “what would happen if we worked together to create a community dedicated to the production of a psychology worthy of the human needs we are meant to address?” By appealing to the better nature of out clients (e.g., self-acceptance, mindfulness, values, commitment) we seem to be creating change in the clinic. Similarly, by raising our sites as professionals and creating a supportive, open, generous culture the same might happen in our training programs, clinics, and research teams. For those of us in the ACT / RFT / Contextual Psychology community we do not think that basic and applied science can safely stand apart. We seek the creation of a new empirical contextual psychology that carries forward and deepens our intellectual tradition, revitalizing basic psychology and linking our work to principles that help us address problems of human suffering and human growth. We want to see us create a psychology more adequate to the challenges of the human condition. This was part of the original vision of behavioral psychology and behavior therapy. Behavioral psychology lost its way over the issue of human cognition, and traditional CBT resulted, but perhaps we have found a way forward that will go beyond the excessively narrow goal of empirically evaluated technologies, to include also the two other aspects of our original tradition that were left behind: a firm link of application to basic principles, and an expansive vision of a form of psychology that can help create a better world in every area of human life. If we can do that, psychology itself may become more robust and useful. That is the vision.

- Posted 2005-07-31

ACT is more than 40 years old.

The personal insight that led to ACT is described by Steve Hayes in this TEDx talk: bit.ly/StevesFirstTED. By his best memory, that moment on the carpet (you will understand that phrase if you see the talk) was in the winter of 1980-81. But that was just a transformational moment. ACT began to form in Steve's lab soon after. The lab members at the time included Robert Zettle ("the Z"), Zamir Korn, and Irwin Rosenfarb. The lab was jointly run with the late Aaron Brownstein, a basic behavior analyst.

The first ACT protocol was written by Steve in 1981. ACT was called "Comprehensive Distancing" -- the lab nickname for it was "Big D." You can find the protocol in the "History of ACT" daughter page of the "About ACT" section of the website.

The first actual ACT study was done in 1981-1982 and was presented at ABCT (then called AABT) in 1982: 

Hayes, S. C., Korn, Z., Zettle, R. D., Rosenfarb, I., & Cooper, L. (November 1982). Rule‑governed behavior and cognitive behavior therapy: The effects of comprehensive cognitive distancing on pain tolerance. Paper presented at the meeting of the Association for Advancement of Behavior Therapy, Los Angeles. 

Steve held back on publishing it despite its success, thinking that the implications were too large and thus outcome studies should not be a focus (especially randomized outcome studies) until its model and methods were better understood and idiographically tested. That is why this very first study was published 17 years later: Hayes, S. C., Bissett, R., Korn, Z., Zettle, R. D., Rosenfarb, I., Cooper, L., & Grundt, A. (1999). The impact of acceptance versus control rationales on pain tolerance. The Psychological Record, 49, 33-47. The only randomized outcome study published directly from the lab in this era was Rob Zettle's dissertation which came out in 1986.

The first ACT training was in 1982: Hayes, S. C. (October 1982). Cognitive distancing and psychopathology. Presentation to Broughton Hospital, Morganton, NC.

"Comprehensive distancing" seamlessly morphed into ACT as we think of it today. The first time "acceptance and commitment therapy" was used in the title of a talk was in 1991: Wilson, K. G., Khorakiwala, D., & Hayes, S. C. (May 1991). Change in Acceptance and Commitment Therapy. Paper presented at the meeting of the Association for Behavior Analysis, Atlanta. The first time it appeared in the title of a journal article was Hayes, S. C. & Wilson, K.G. (1994). Acceptance and Commitment Therapy: Altering the verbal support for experiential avoidance. The Behavior Analyst, 17, 289-303.

The ACT community has agreed not to set up our own therapist certification. There is a process to recognize ACT trainers. ACT trainers sign a values statement agreeing to make their training protocols available for low cost or no cost and agreeing not to make proprietary claims or to certify therapists.

Why reject therapist certification? Two reasons: it ossifies the method, and creates a hierarchy that cannot be readily dismantled. Instead, the ACT community provides ways to increasing sophistication and ability; conducts studies on training methods; and encourages all ACT therapists to constantly improve. On the website, therapists can list themselves as ACT therapists whenever they choose, but are asked to list their training experiences.

It has several functions but the bottom line is that it is the whole ACT model in one exercise Because it is uncomfortable but not dangerous it is a great context in which to practice defusion and acceptance. Its social nature heightens that part of it, since outright avoidance is relatively unlikely once people agree to do it. You can use psychological contact with the other as a metric of being present, so it gives feedback on the costs of fusion and avoidance. When these processes interfere the other person disappears Because self-as-context is social in origin, if the person running the exercise orients the participants to it you can contact the deictic basis of consciousness. The other person becomes somehow connected to you -- and yet you yourself contact a sense of transcendence in that social connection Because almost everyone values people, if you ask folks to use this as a physical metaphor for connection with others, it puts the mindfulness work (the work on acceptance, defusion, self, and the present) into a values context. You see how these processes support valued actions. It is a commitment exercise because you get agreement before hand; and again the social nature of it helps maintain the commitment And it is an exercise in psychological flexibility because it brings all of the other processes together in an unusual and repertoire expanding action It is the whole model in 10 minutes - Steve Hayes