What is Acceptance and Commitment Therapy?

Acceptance and commitment therapy (usually pronounced as the word “act” rather than the initials “A-C-T”) is a form of clinical behavioural analysis developed in 1986 by psychologists Steven Hayes, Kelly Wilson, and Kirk Strosahl. Originally called comprehensive distancing, it gets its current name from one of its core messages: the injunction to accept what is out of one’s personal control and commit to action that improves and enriches one’s life. Thus, ACT:

  1. Is an empirically-based set of psychological interventions that
  2. Uses mindfulness skills to develop psychological flexibility and
  3. Helps clarify and direct values-guided behaviour (Carrasco, 2013; Wikipedia, 2013; Harris, 2013).

What are ACT’s goals?

ACT aims to maximise human potential in order to create a rich and meaningful life, while accepting the pain that inevitably goes with it. It teaches those practicing it – let’s say that’s us – to accept things that are out of our control (this does not mean that we approve them) without evaluation or attempts to change them (unlike in Cognitive Behavioural Therapy), while committing to taking action that enriches our life. ACT therapy achieves this by:

  • Helping us to clarify what is genuinely important and meaningful (that is, our values) and to use that knowledge to inspire and guide us to set life-enriching goals;
  • Teaching psychological skills, known as mindfulness skills, for handling painful thoughts, feelings, urges, images, and memories (called private experiences) in such a way that they have much less impact on us. Developing a new mindful relationship with such experiences frees us to take action consistent with our values (Harris, 2006; Carrasco, 2013; Harris, 2009).

What is the underlying philosophy of ACT?

ACT is based on the pragmatic philosophy of Relational Frame Theory (RFT), a comprehensive theory of language and cognition that is derived from behaviour analysis. While traditional models of language and cognition go for an information transmission system, RFT uses a functional, contextualistic approach to understand complex human behaviour such as language and thought (Wikipedia, 2013; Fox, 2013).

Translated into simpler language, the above paragraph means that RFT refers to the way that the stimulus functions of a thing or event tend to get transferred to the word used to describe it. For instance, let’s say that you are afraid of snakes. Every time you see one, you experience a knot of fear in your stomach, you break out into an anxious sweat, and you have an overwhelming desire to run away. RFT understands that if someone merely utters the word “snakes” in your presence (the stimulus), you are likely to experience the same fear, anxiety, and desire to run as if you were confronted by a live snake.

Because all of us as human beings contain a huge storehouse of anxiety hidden in our personal histories, we also have a wealth of potential anxiety that could be experienced in our personal futures. In the present, thoughts can occur that remind us of anxiety we experienced in the past, and we may anticipate anxiety that could occur in the future. Thus, according to the principles of RFT, words become causes of pain. We hear someone talking about their grief from losing their father, and we re-experience our own similar grief. All that we have been exposed to is the other person’s words; we haven’t just experienced another bereavement, but the words of grief we are hearing evoke automatic thoughts and feelings as though the death were occurring right here and now.

We tend to take these words, these thoughts, literally, rather than observing them as thoughts. Thus language and thought ends up being able to hurt us, because through it, pain can be brought to our minds at any time. It cannot be avoided. The more we try to avoid the painful experience (through distraction, repression, substance abuse, and many more short-term strategies), the more it lingers, causing us anxiety, fear, sadness, pain, shame, and other difficult emotions. If we didn’t have language, we could not call up a negative past, nor anticipate a negative future. But the way our minds tend to deal with this pain makes things worse. We tend, as human beings, to set up an unwritten rule that suffering is bad, that the absence of suffering is good, and that if something is bad, we should try to get rid of it by acting on it directly (NWLCB Training, n.d.).

Enter Acceptance and Commitment Therapy. Working with the RFT model of language and cognition above, ACT helps people to relieve their suffering by dealing with painful experiences and thoughts – which RFT and ACT both acknowledge cannot be controlled long-term – by accepting them, and committing to actions which create a rich and purpose-filled life. Thus, the underlying philosophy of ACT (that is: RFT) is pragmatic, and precise, relying on just a few basic concepts to account for language and thought, with directly observable principles. It has direct applied and clinical applications, and is based on empirical research. Proponents say that it is taking behavioural science into exciting new directions with profound implications for almost every topic relating to complex human behaviour (Wikipedia, 2013; Fox, 2013).

Where does ACT “sit” within schools of therapy?

Russ Harris, a general practitioner-turned-psychotherapist who has actively promoted the concepts of ACT through his writings, web presence, and training workshops, has commented that ACT is hard to describe, but can best be thought of as an “existential humanistic cognitive behaviour therapy” (Harris, 2009, p. 21). ACT is one of the “third wave” behavioural therapies, along with Dialectical Behaviour Therapy (DBT), Mindfulness-Based Cognitive Therapy (MBCT), and Mindfulness-Based Stress Reduction (MBSR) (you can read a bit about these in the MHA Mindfulness course). All four focus on the development of mindfulness skills.

Waves of behaviour therapies

So if ACT is the third wave, what were the first and second waves, you ask? Good question. The “first wave” of behavioural therapies, while started in the 1920s, became well-known in the fifties and sixties. These therapies looked at observable behavioural change and were characterised by their techniques of operant and classical conditioning: what is traditionally known as behaviourism. The “second wave” began in the seventies when practitioners allowed cognitive interventions to be included, and therapies such as Rational-Emotive Behaviour Therapy (REBT) and Cognitive Behaviour Therapy (CBT) grew in popularity, the latter eventually coming to dominate the “wave” (Harris, 2006).

Differences between ACT and other behaviour therapies

Clearly, there has been a growing trend to allow increasingly broader aspects of the client to come under study. Classical behaviourism, the first wave, looked only at behaviour. Therapies such as REBT and CBT in the second wave included both behaviour and cognition (thought and belief) as valid aspects to study in order to understand a human being. Third wave therapies, in their focus on mindfulness, additionally allow the aspect of awareness (that is, an aspect larger than the Western conception of “mind”) as a valid focus.

Within the current wave, ACT differs from the other therapies in several ways. First, MBSR and MBCT (the mindfulness approaches to stress reduction and cognitive therapy) are chiefly manualised protocols, designed to help groups of people in the treatment of stress or depression. DBT is often a combination of group skills training and individual therapy, created particularly to help those with Borderline Personality Disorder (Baer, 2003). Conversely, ACT can be used with a variety of clinical populations – as individuals, couples, or groups – in therapy sessions which can be brief, medium-term, or long-term. ACT encourages therapists to create or individualise their own mindfulness techniques (even co-creating them with clients) rather than relying on manualised procedures. And ACT views formal mindfulness meditation as only one way within a wide range of methods to teach mindfulness skills (Harris, 2006).

The evidence

Sounds interesting, you may say, but does it work? The good news here is that there is a growing body of evidence to support practitioners’ claims, both in terms of the size and degree of control of the trials, and also in regard to the areas in which ACT interventions have been deemed to be successful. Here are a few:

ACT is considered an empirically validated treatment by the American Psychological Association; it has given the status of “modest research support” in depression and “strong research support” in chronic pain (APA Presidential Task Force on Evidence-Based Practice, 2006).

ACT is listed as evidence-based by SAMSA (the Substance Abuse and Mental Health Services Administration) in the United States (SAMSHA’s National Registry of Evidence-Based Programs and Practices, 2013). It has randomised trials for ACT in the areas of psychosis, work site stress, and Obsessive Compulsive Disorder.

ACT has demonstrated preliminary evidence of effectiveness in randomised trials for a variety of presenting issues including:

  • Chronic pain
  • Addictions
  • Smoking cessation
  • Depression
  • Anxiety
  • Psychosis
  • Workplace stress
  • Diabetes management
  • Weight management
  • Epilepsy control
  • Self-harm
  • Body dissatisfaction
  • Eating disorders
  • Burnout (Hayes, 2013)

Key ACT processes, such as acceptance, defusion, and values clarification, seem to be playing a causal role in producing beneficial clinical outcomes (Lundgren, Dahl, & Hayes, 2008), and more, the reverse may true. Correlational studies are showing that absence of these processes predicts psychopathology. ACT processes account for, on average, 16 – 29 per cent of the variance in psychopathology according to a recent meta-analysis (Forman, Herbert, Moitra, Yeomans, & Geller, 2007; Zettle, Rains, & Hayes, 2011).

In New Zealand, a 2010 study was conducted to examine the effectiveness of ACT therapy, in the form of self-help books, for people with chronic pain. With a sample size of 24, the researchers made sure that subjects in the experimental group had sufficient reading comprehension, no psychiatric disorder, stable medication, and no history of trauma. The method used was two group study conducted over a six-week period, with some participants required to read the self-help book and complete the exercises. Pre- and post-intervention questionnaires revealed that the experimental group (those reading the ACT self-help books) had statistically significant improvements, with large effect sizes, for acceptance, satisfaction with life, and quality of life. Medium effect sizes were obtained for enhancement in pain ratings (Johnston, Foster, Shennan, Starkey, & Johnson, 2010).

A recent meta-analysis of 68 laboratory-based studies on ACT components has given support to the connection between psychological flexibility and some of ACT’s components (Levin, Hildebrandt, Lillis, & Hayes, 2012).

This article was adapted from the upcoming Mental Health Academy CPD course “Acceptance and Commitment Therapy: Basics and Techniques”. This course covers the basic concepts and techniques of Acceptance and Commitment Therapy (ACT), and we invite you to examine as we go through the material, just how and why it may be effective with clients.


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  • Fox, E.  (2013). Advantages of RFT.  Association for Contextual Behavioral Science.  Retrieved on 16 July, 2013, from: hyperlink.
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  • Zettle, R. D., Rains, J. C., & Hayes, S. C. (2011). Processes of Change in Acceptance and Commitment Therapy and Cognitive Therapy for Depression:  A Mediation Reanalysis of Zettle and Rains. Behavior Modification 35 (3): 265–83. doi:10.1177/0145445511398344. PMID 21362745.