This chapter provides a comprehensive review of the theory and research on
Acceptance and Commitment Therapy (ACT). The chapter will begin by outlining the
theoretical basis of ACT and the ACT model of psychopathology, which accounts for the
occurrence of psychological distress via two key constructs: experiential avoidance and
cognitive fusion, together which produce psychological inflexibility. The second part of the
chapter will focus on the translation of the ACT model into clinical practice, by describing
the core treatment processes of ACT: creative hopelessness, acceptance, cognitive defusion,
mindfulness, self-as-context, values, and committed action. The third part of the chapter will
outline the differences between ACT and cognitive behavioural therapy (CBT), the current
dominant psychotherapeutic modality, in order to further illuminate the unique theoretical
features of ACT, and how these translate into clinical practice. The final part of the chapter
will review clinical studies on ACT for depression, anxiety and transdiagnostic psychological
problems in order to establish the empirical evidence base for ACT, and to support the
application of ACT to the treatment of emotional disorders in particular. In the conclusion of
this chapter, it is argued that there is a need for more research on the effectiveness of ACT for
a range of psychological issues.
Theoretical basis
At a broad level, acceptance and commitment therapy (ACT; Hayes, Strosahl &
Wilson, 1999) is a mindfulness, acceptance and values-based psychotherapy that is grounded
in behavioural and cognitive theory (Hayes, Masuda, & De Mey, 2003). In contrast to other
therapeutic approaches, such as cognitive behavioural therapy (CBT), ACT is somewhat
philosophical level, ACT is grounded in functional contextualism (Hayes, 1993; Hayes,
Hayes, & Reese, 1988; Biglan & Hayes, 1996), a philosophy of science which consists of a
number of assumptions and rules used to construct and test theories.
Functional Contextualism serves as a philosophical basis for Relational Frame Theory
(RFT; Hayes, Barnes-Holmes, & Roche, 2001), which is the theoretical foundation of ACT.
RFT is a theory of language and cognition that attempts to explain how human beings infer
relationships between arbitrary objects (Fox, 2006). A detailed discussion of RFT is beyond
the scope of this thesis (see Hayes et al., 1999, for a comprehensive explanation of both
functional contextualism and RFT), however the basic premise of RFT is that humans form
relationships between stimuli via language and cognition, and that individuals respond to
stimuli (or “verbal events”; Hayes et al.) based on these relationships. According to RFT,
once the “relational frame” around two stimuli has been established it acts as a cue for how the stimuli will be responded to in the future, and once this frame has been created it is very
difficult to break (Wilson & Hayes, 1996). For example, if an individual forms an association
between a particular feeling (anxiety) and a specific situation (public speaking), it is likely
that future encounters with the situation or even thoughts about the situation will elicit the
feeling. Thus, according to RFT, the “events” themselves (anxiety; public speaking) are not what matters, it is the relationships that exist between these events that give them their
meaning and their psychological functions.
The ACT Model of Psychopathology
On the grounds of RFT, ACT emphasizes the role of the context rather than the
content of language and cognition in psychological distress. According to this model, there
are no thoughts, feelings, or other private experiences that are faulty or “wrong”, and
al., 1999). Rather, it is the way individuals relate to these private experiences through
language and cognition that is potentially harmful, for example, through the assumption that
these experiences must be controlled or suppressed in order to reduce distress, or through an
over-reliance on beliefs, rules, fears, and judgments in the regulation of behavior.
Within an ACT framework, there are two key processes which represent maladaptive
ways of relating to private experiences: experiential avoidance and cognitive fusion. These
constructs are seen as contributing to the development and maintenance of psychopathology
via the effects of language. Experiential avoidance occurs when a person is unwilling to
remain in contact with particular private experiences (e.g. thoughts, emotions, urges, bodily
sensations, memories), and involves “mental and behavioural strategies aimed at changing the form or frequency of one’s current internal experience” (Orsillo, Roemer, & Holowka, 2005, p.11). These strategies can include either suppression, which involves active attempts
to control and/or eliminate the experience of negative private events; or situational avoidance,
which constitutes the avoidance of or escape from contextual factors which are associated
with the emergence of unwanted private experiences (Hayes et al., 2004). Hayes and
colleagues (1999) suggest that experiential avoidance has evolved from the generalization of
cultural rules which suggest that negative thoughts and emotional states can and should be
controlled. For example, common phrases such as, “look on the bright side”, “boys don’t cry”, and “just forget about it”, for example, are seen as perpetuating the idea that one can achieve control over their internal experiences, which creates further distress for individuals
when attempts at control are futile (Hayes et al., 2004). According to ACT, experiential
avoidance leads to a long-term increase in the frequency and intensity of difficult private
A number of studies across different domains of research have demonstrated the
negative impact of experiential avoidance. In the coping literature, emotion-focused and
avoidant strategies have been found to negatively predict outcome in depression (De Genova,
Patton, Jurich, & MacDermid, 1994), substance abuse (Ireland, McMahon, Marlow, &
Kouzakanani, 1994), and recovery from child sexual abuse (Leitenberg, Greenwald, & Cado,
1992). The research on thought suppression indicates that attempting to suppress a thought
results in it rebounding to a greater intensity than its original state (Wenzlaff et al., 1988).
Wegner and Zanakos (1994) found that depressive symptoms are increased in individuals
who exhibit trait-based avoidance of emotions, particularly when this is also combined with
thought suppression. In a review of studies looking at the relationship between
psychopathology and experiential avoidance, Ruiz (2010) found that the weighted
correlations between the experiential avoidance and depressive and anxiety symptoms were
r=.55, and r=.52 respectively. Finally, Hayes et al. (1999) suggest that the incorporation of
acceptance (the antidote of experiential avoidance) and mindfulness components into a
number of established psychotherapies (including Dialectical Behaviour Therapy, Linehan,
1993; behavioural marital therapy, Jacobson, 1992; Jacobson, Koerner, & Christensen, 1994;
and emotion-focused therapy, Greenberg & Johnson, 1988) has improved treatment outcomes
is indicative of the role of avoidance in psychological distress. Overall, this literature presents
convincing evidence for the detrimental effects of experiential avoidance and its role in
psychological suffering.
Cognitive fusion is defined as “fusing with or attaching to the literal content of private experiences whereby we respond to a thought or feeling not just as a thought or feeling but as
the actual event it describes” (Eifert & Forsyth, 2005, p.88). According to ACT, human beings’ over-reliance on verbally-derived relationships between stimuli means that they are
vulnerable to becoming “fused” with the content of cognitions (Hayes et al., 1999). Through the process of cognitive fusion, thoughts and the actual stimuli or events represented by these
thoughts become fused together, such that the functional properties of the stimuli can be
present in a psychological sense. Hayes and colleagues suggest that the fact that thoughts can
produce panic symptoms is an example of cognitive fusion, because the individual is reacting
as if the feared situation is immediately present. The ACT model emphasizes that thoughts
themselves are not problematic – rather, it is the fusion with and subsequent avoidance of
thoughts, feelings and situations that leads to distress (Hayes et al., 1999).
In view of its conceptualization of psychopathology and philosophical and theoretical
foundations, ACT does not attempt to reduce, change, suppress or avoid thoughts, feelings,
memories, urges, and emotions. Rather, it aims to reduce the impact or influence of painful
private events on the individual (Harris, 2006). ACT views human suffering as normal, and
rejects the notion that happiness is dependent on the absence of negative affect (Hayes et al.,
1999). Thus, symptom reduction is not an explicit goal of ACT, rather it is seen as a natural
consequence of acceptance, defusion from unwanted thoughts, increased engagement with
the present experience, and increased engagement in values-consistent action.
Core Treatment Processes
In terms of intervention, the two major goals of ACT are to foster (a) acceptance of
problematic, unhelpful thoughts and feelings that cannot be controlled, and (b) commitment
and action toward living a life that is consistent with one’s values (Eifert, Forsyth, Arch, Espejo, Keller, & Langer, 2009). These goals are achieved through the six core treatment
processes of ACT: acceptance, defusion, contact with the present moment (through
mindfulness), the observing self (self-as-context), values, and committed action. In ACT,
are introduced as needed based on the client’s presentation, and are revisited and utilized in a
dynamic way throughout the therapeutic process. An additional component of ACT called
“creative hopelessness” is incorporated early in treatment, as a means of motivating the client to recognize the futility of control and avoidance behaviours.
Given ACT’s stance that language is the cause of psychological suffering, therapeutic processes and techniques such as metaphors and experiential exercises are employed to
overcome the trap of language. Hayes and colleagues (1999) maintain that changing verbal
relations by adding new verbal relations elaborates the existing network of such relations in
the mind rather than eliminating it, and that the most effective way of weakening verbal
relations is to change the context supporting the verbal process, rather than by focusing on the
verbal content. In other words, maladaptive and distressing cognitive content cannot be
ameliorated with more cognition, and thus ACT is aimed at facilitating growth through
engagement with the present moment, where real opportunity for change is thought to occur.
Creative Hopelessness.
Generally the first therapeutic component in ACT protocols, creative hopelessness
involves helping the client to realize that past efforts to change, control and avoid difficult
thoughts, feelings, sensations, memories and so forth have not worked, and that the struggle
with these difficult private experiences has actually impeded the client’s ability to engage in valued life activities.
Metaphors and experiential exercises are utilized to raise the client’s awareness of the various ways in which they have attempted to both avoid and control difficult internal
experiences, for example, through substance use, therapy, positive thinking, numbing, and so
forth, thereby establishing the futility (and the costs) of these efforts. The ideal outcome of
“unworkable change agenda” which has been instilled in them by broader society, that is, the notion that symptom control is a prerequisite for living a happy, fulfilling and successful life
(Eifert et al., 2009). Once the individual gains insight into the fact that this agenda is not
actually effective, the rationale for acceptance as an alternative to control and avoidance is
established.
Acceptance.
Acceptance within ACT is defined as “an active taking in of an event or situation… [an] abandonment of dysfunctional [symptom] change agendas and an active process of
feeling feelings as feelings, thinking thoughts as thoughts… and so on” (Hayes et al., 1999, p.77). Acceptance involves opening up to and making room for thoughts, feelings, sensations,
urges, and memories, and the client is encouraged to adopt a stance of willingness in the face
of the difficult internal experiences that human beings inevitably face. The notion of
acceptance in ACT represents the antithesis to the idea that symptoms must be controlled or
avoided and that difficult thoughts and feelings need to be absent in order for meaningful
therapeutic change and psychological health to occur. Therefore, ACT offers acceptance as
the alternative to avoidance, and it is cultivated in therapy to counter the client’s efforts to avoid their difficult private experiences. Importantly, however, acceptance is not framed as
being an end in itself, but rather it is developed and used to enable values-consistent change
to occur in the individual’s external world (Cullen, 2008).
The ACT therapist encourages acceptance through the use of metaphors and
mindfulness techniques. The client is encouraged to experience affect states and bodily
sensations, such as anxiety, in the moment, as they occur, rather than trying to control the
early on in ACT sessions, and the practice of acceptance and willingness is thought to allow
for valued and committed action to occur.
Cognitive Defusion.
Cognitive defusion is employed in ACT to undermine cognitive fusion with thoughts
that perpetuate psychological distress and inhibit value-based action. It is ACT’s major tool
for dealing with difficult and distressing thoughts, and unlike cognitive therapy, it emphasizes
altering the context rather than the content of thought. That is, within an ACT framework, the
specific thoughts a client has are not important; what is significant is the meaning people
attach to their thoughts and the context in which certain thoughts occur. In light of this, the
cognitive defusion component of ACT is aimed at weakening the literality of difficult
thoughts (Cullen, 2008), so that the individual is able to avoid getting “caught up” in specific thoughts as well as in the “ruminative trap of cognition” (Arch, 2008, p. 266).
Cognitive defusion is facilitated in therapy via experiential exercises, through which
the client is taught to distance themselves from the literal meaning and content of language
(by seeing thoughts as thoughts instead of facts), and to be mindful of the continuous ebb and
flow of thoughts. For example, a particularly distressing thought, such as “I am worthless” will be inspected, spoken out loud, and repeated until it is seen for what it actually is – a
group of words – rather than the actual painful event it describes (Cullen, 2008). Cullen
highlights the parallels between cognitive defusion techniques and exposure therapy, in that
the more an individual can stay in contact with a painful or uncomfortable thought or feeling,
the more likely that the distress associated with that thought or feeling will diminish.
Mindfulness.
Mindfulness, which involves the practice of being deliberately and purposefully
“being present” as “flexible, fluid, and voluntary attention to internal and external events as they are occurring, without attachment to evaluation or judgment” (p. 503). Thus,
mindfulness is considered to help the client to live fully and purposefully in the moment,
while accepting difficult private experiences and decreasing the negative impact of language
and cognition (Twohig, 2012). Mindfulness is not unique to ACT, with many other
therapeutic modalities incorporating this practice, several which were published prior to ACT
(e.g., Kabat-Zinn, 1990; Linehan, 1993).
In ACT, mindfulness goes hand-in-hand with the notion of self-as-context or the
observing self. The combination of these processes is aimed at assisting the client to
experience being in the present moment, observing the self and the surrounding environment,
rather than living in their mind and ruminating over past events or worrying about the future
(Arch & Craske, 2008; Cullen, 2008). The individual is taught to recognize when they are
not in the present, and to flexibly shift their attention (Twohig, 2012). Mindfulness is also an
important element of ACT as it helps to counteract experiential avoidance strategies aimed at
controlling or reducing discomfort.
Self-as-Context (The Observing Self).
As discussed, ACT endorses the differentiation between the content of internal
experiences and the context in which these experiences occur (Strosahl, Hayes, Wilson, &
Gifford, 2004). That is, distinguishing the “conceptualized self”, or the image of the self that is derived from one’s thoughts, feelings, memories and roles, from the “self-as-context”, or the self that is constant, and which acts as the neutral setting in which these events occur.
Twohig (2012) suggests that people attempt to protect or retain the conceptualized self even
they may continue to engage in behaviours that perpetuate that self-description, in order to
protect the self.
ACT interventions work to develop the individual’s sense of self-as-context in order
to assist the client to disentangle themselves from their symptoms and to promote
psychological flexibility. With this sense of self, the individual can experience internal and
external events and experiences, without being defined by them.
Values.
The strong and explicit emphasis on values in ACT differentiates it from other
therapeutic approaches. Arch and Craske (2008) argue that the ultimate goal of ACT therapy
is for the client to achieve valued living (via values-driven behavior), and that this is one of
the major ways in which ACT differs from CBT, for which symptom reduction is the primary
therapeutic objective. Together with committed action, understanding and clarifying values
are ACT’s “activation processes”, which assist clients to move forward in their chosen life directions (Cullen, 2008).
Values can be contrasted with goals in that they are pursued in an ongoing way across
one’s life, whereas goals are obtainable. In ACT, various exercises are used to assist the client to uncover and clarify their values, in order to help them to regain a sense of life
direction that is consistent with these values (Strosahl et al., 2004). For example, the “epitaph exercise” aims to elicit the client’s values by asking them to imagine what they would like to be written about the kind of person they were on their tombstone. As foreshadowed, value-
guided exposure is also utilized in ACT, with the aim of increasing one’s ability to live in accordance with their values, while mindfully accepting difficult thoughts and feelings (Arch
Committed Action.
ACT is a behavioural therapy, and the therapeutic component of committed action is a
key aspect of therapy. Committed action involves the client choosing to behave in ways that
are consistent with their values, and part of the goal of this phase of treatment is to show the
client how to gradually build patterns of sustainable, committed, value-driven behaviour
(Strosahl et al., 2004). Thus, traditional behavior change procedures such as goal-setting are
incorporated into therapy, and barriers (in the form of challenging thoughts, emotional
reactions, and other difficulties) are prepared for and worked through. Any behavioural
intervention, including exposure exercises and skills training, can be incorporated at this
stage as long as it is consistent with ACT processes and principles (Twohig, 2012). What
differentiates the committed action component of ACT to behavioural aspects of other
therapies is the motivation behind engaging in the behavior – for example, while exposure to
feared stimuli may be incorporated into ACT, it is used to assist the client to accept
uncomfortable feelings and thoughts so that they can live in better alignment with their
chosen values, as opposed to being aimed solely at fear extinction. Thus, the client practices
acceptance, defusion, and mindfulness, and self-as-context to deal with potential difficult
private experiences that may come up for them as they engage in committed action based on