Acceptance and commitment therapy (ACT)

Article written and reviewed by Dr Luca Moretti

Acceptance and Commitment Therapy (ACT), known in Italian as terapia di accettazione e impegno, is a contextual behavioral psychotherapy developed within the so called third wave behavioral therapies. Its central aim is to increase psychological flexibility, meaning the ability to make contact with present experience and choose behaviors consistent with personal values even in the presence of unpleasant thoughts, memories, sensations or emotions. In depression, ACT does not start from the idea that the patient must eliminate every negative mental content before being able to act, but works on the relationship with these experiences and on patterns of avoidance or rigidity that may progressively narrow the person's life.

ACT shares behavioral roots with behavior therapy and some experiential elements with mindfulness based interventions, but it has its own theoretical model and a distinct set of processes. Compared with classical cognitive therapy, it does not prioritize evaluating the truth of thought content or systematically restructuring it; instead, it seeks to reduce the rigid control that language exerts over behavior through defusion, acceptance and orientation toward values. This difference does not imply that either strategy is universally superior to the other.

The ACT literature has grown considerably. Meta analyses specifically addressing depression published in 2023 and 2025 show benefits for depressive symptoms compared with various control conditions, while broader reviews emphasize that comparisons with other bona fide psychotherapies do not demonstrate consistent superiority. For major depression, ACT can therefore be considered an empirically supported intervention, but its degree of consolidation in major guidelines is not as uniform as that of approaches such as CBT, behavioral activation or IPT.

Theoretical model: psychological flexibility and psychopathology

The ACT model describes persistent psychological distress in terms of psychological inflexibility. Painful thoughts and emotions are not considered pathological in themselves: they become particularly limiting when a person rigidly organizes behavior to control, suppress or avoid them, or when the person treats their content as a literal command determining what they can or cannot do. In depression, this pattern may manifest as withdrawal, inactivity, rumination, avoidance of feared situations, loss of contact with meaningful activities and progressive narrowing of the behavioral repertoire.

Experiential avoidance describes persistent attempts to avoid or alter unwanted internal experiences even when those strategies carry high long term costs. Not all avoidance is dysfunctional, and ACT does not prescribe passive acceptance of dangerous or modifiable situations. The clinical problem is functional rigidity: a strategy becomes maladaptive when it dominates behavior regardless of context and moves the person away from important goals and values.

Cognitive fusion refers to a relationship with language in which the content of a thought is experienced as though it coincided with reality or constituted a mandatory rule. A thought such as “I am worthless”, for example, may guide avoidance as if it were a definitive description rather than a mental event. Defusion does not necessarily seek to replace that thought with a more positive one: it aims to change the function of the thought and make it less dominant over behavior.

The ACT model has been linked to Relational Frame Theory, a research program on human language and cognition. This theoretical foundation provides a framework for explaining how verbal functions and learned relations can influence behavior, but it does not mean that every component of the theory has been demonstrated to be a necessary causal mechanism of depression. It is important to distinguish the coherence of the clinical model from empirical evidence for individual mediators.

In depression, psychological flexibility is therefore understood as the capacity to make room for difficult internal experiences, observe thoughts with greater distance, orient attention to the present and choose behaviors consistent with values. Symptom reduction remains an important clinical outcome, but it is not pursued through a continuous struggle to control every internal state. Treatment instead evaluates whether the patient's behavioral repertoire is becoming broader, more functional and more consistent with what the patient considers meaningful.

The six ACT processes

The classic model organizes the intervention around six interconnected processes. They do not constitute a rigid sequence or six isolated techniques; the therapist uses them functionally according to the case formulation. Their graphic representation is often called the “hexaflex”, but in clinical practice the central issue is identifying which rigidity processes are limiting behavior and which modes of flexibility can be trained.

• Acceptance: willingness to make contact with unavoidable internal experiences without automatically organizing behavior to eliminate them.
• Cognitive defusion: changing the relationship with thoughts, images and memories so that they are experienced as mental events rather than commands or absolute truths.
• Contact with the present moment: flexibly orienting attention toward current experience instead of being rigidly captured by rumination, the past or anticipation.
• Self as context: developing a perspective from which thoughts, emotions and roles can be observed without completely equating them with personal identity.
• Values: clarification of qualities of action and freely chosen life directions, distinct from specific goals or social prescriptions.
• Committed action: building and maintaining concrete behaviors consistent with values, with adjustments according to consequences and real obstacles.

Acceptance does not mean resignation and does not imply approving abuse, discrimination, medical conditions or modifiable practical problems. In ACT, acceptance primarily concerns internal experiences that cannot be eliminated on command when attempts at control carry greater costs. When facing danger or a concrete problem, values consistent action may consist precisely of changing the environment, seeking help or leaving the situation.

Values are not goals to be achieved once and for all. They represent directions, for example behaving as a reliable person in relationships or caring for one's health. Goals that can be translated into actions, by contrast, make it possible to assess whether treatment is producing change. In depression, this distinction helps construct realistic steps even when motivation and pleasure are reduced.

Self as context is one of the more abstract processes and requires careful clinical formulation. It should not be presented as a metaphysical truth or as dissociation from one's own experience. Exercises instead aim to foster a stable observing perspective toward the changing contents of experience, reducing rigid identification with depressive labels such as “I am a failure”.

Assessment, techniques and delivery of therapy

Before treatment, diagnostic and safety assessment similar to that required for other psychotherapies for depression is necessary. Severity, temporal course, functioning, suicide risk, possible manic or psychotic symptoms, substance use, comorbidities and ongoing treatments should be explored. ACT does not replace psychiatric assessment and does not make pharmacotherapy unnecessary when medication is indicated.

Functional formulation identifies situations, internal experiences, control strategies and short and long term effects. An apparently similar behavior may serve different functions: staying at home may represent necessary recovery in one context and rigid avoidance in another. The therapist therefore avoids automatically classifying a behavior as healthy or pathological and instead seeks the functional relationships that maintain the problem.

Techniques include experiential exercises, metaphors, mindfulness, observation of language, values clarification, exposure to avoided internal experiences and planning concrete actions. In defusion, exercises can be used to make the verbal nature of thought more apparent, for example by prefacing it with “I am noticing the thought that...”, repeating a word until its semantic function is temporarily reduced, or observing mental images without trying to push them away. These tools are means, not mandatory rituals.

Exposure in ACT is consistent with the principle of increasing willingness to make contact with experiences necessary for a meaningful life. It is not used to prove that anxiety or sadness must disappear immediately. Therapeutic response is also evaluated through increases in effective action and participation in important contexts, not only through the subjective feeling of being calmer during the exercise.

Values clarification should avoid stereotyped or moralistic answers. The therapist helps the patient distinguish chosen values from external expectations and translate them into gradable actions. In severe depression, an initial goal may be very small and concrete. Committed action does not presuppose high motivation: as in behavioral activation, action may precede improvement in mood, although it is conceptualized differently.

There is no single number of sessions that applies to every ACT protocol. The literature includes individual, group, brief, more extended and digital interventions, often in heterogeneous populations. It is therefore inappropriate to automatically transfer duration and efficacy from one protocol to another. For clinical depression, it is preferable to use studied protocols, trained therapists and repeated outcome measurement.

Evidence of efficacy in depression

ACT studies include numerous disorders and medical conditions, so a transdiagnostic meta analysis is not automatically equivalent to evidence specific to major depression. Reviews specifically focused on depression are more informative for this indication. The 2023 meta analysis by Zhao and colleagues, based on randomized trials in depressive disorders, reported benefits of ACT for symptoms compared with waiting lists or treatment as usual, with less favorable results in some comparisons with CBT or cognitive therapy.

A subsequent 2025 systematic review and meta analysis specifically devoted to ACT in depression expanded the body of studies and supports an overall antidepressant effect. At the same time, trial quality, heterogeneity of comparators, sample sizes and risk of bias require caution when quantifying the effect and generalizing it to all patients with major depression.

Broader reviews of ACT show favorable results compared with treatment as usual or inactive controls, but comparisons with bona fide psychotherapies tend to be smaller and less consistent. The updated 2026 systematic review of ACT RCTs reinforced this point: the overall evidence does not support the idea that the ACT model is generally superior to other legitimate active psychotherapies. This distinction is essential for scientifically accurate communication.

According to major depression guidelines, ACT does not occupy the same position as CBT, behavioral activation or IPT in every healthcare system. Absence from a first line list does not demonstrate inefficacy because guidelines differ in date, methodology and evidence thresholds; however, it prevents ACT from being described as a universally preferred treatment. The choice should reflect specific evidence, patient preference and available expertise.

The role of psychological flexibility as a mediator also requires rigorous interpretation. Numerous studies show associations and changes consistent with the model, but demonstrating a causal mechanism requires appropriate temporal and experimental designs. Simultaneous improvement in flexibility and symptoms does not by itself prove that the former caused the latter.

Clinical indications, integration and limitations

ACT may be considered when a patient shows a marked pattern of experiential avoidance, fusion with self evaluative content, withdrawal from meaningful activities or difficulty acting in the presence of painful internal states. However, these elements are formulation targets, not biomarkers or validated selection criteria that predict with certainty a superior response to ACT.

Therapy can be combined with pharmacotherapy when indicated. Psychological treatment does not require discontinuing an antidepressant and does not interpret medication use as experiential avoidance. Any pharmacological change must be agreed with the prescribing professional and based on clinical indications, response, tolerability and relapse risk.

Particular caution is required in presentations involving high suicide risk, mania, psychosis, severe impairment of self care or disorders requiring a specific protocol. Acceptance and mindfulness exercises may be adapted or suspended if they significantly increase destabilization. Therapy must also distinguish internal pain from external circumstances that require protection or concrete change.

A practical limitation is the risk of using ACT language vaguely, turning concepts such as values or acceptance into nonoperational slogans. High quality ACT requires functional analysis, observable goals, outcome monitoring and competence in using the model's processes. The therapist must verify whether the patient is actually broadening behavior and functioning, not merely using the model's vocabulary.

The prognosis of depression treated with ACT depends on disorder severity, chronicity, comorbidities, risk, treatment quality and access to subsequent care. Willingness to experience difficult emotions and increased action consistent with values can be useful goals, but they do not eliminate relapse risk and do not replace a maintenance plan when clinically indicated.

Quality of delivery is another selection factor. Competent ACT requires a functional formulation and coherent use of the model's processes; it is not equivalent to a generic invitation to “accept” what happens. If well structured CBT, BA or IPT is locally available but an adequately trained ACT therapist is not, the higher quality of the available treatment may be clinically more important than a theoretical preference for a specific model. The decision should therefore integrate treatment evidence and the actual competence of the service.

Relationship with CBT, behavioral activation and mindfulness

ACT and CBT share a behavioral foundation and a strong focus on observable procedures, between session exercises and active change. The best known difference concerns treatment of cognitive content: CBT may use cognitive restructuring and testing of interpretations, whereas ACT prioritizes defusion and changing the function of thought. In practice, boundaries may be less clear cut, and competent therapists avoid reducing either approach to a single technique.

With behavioral activation ACT shares the aim of reducing withdrawal and increasing contact with meaningful activities. BA, however, formulates the problem primarily through avoidance, reinforcement and environmental contingencies, whereas ACT links action to values and flexibility processes. The two strategies may produce similar behavioral changes through partly different rationales.

ACT uses present moment awareness exercises but is not the same as a standardized mindfulness program such as mindfulness based cognitive therapy. Mindfulness in ACT is a family of functional processes integrated with defusion, values and action. The amount of formal meditation may be modest or variable and does not by itself define fidelity to the model.

These distinctions are relevant to interpreting studies correctly: an ACT trial should evaluate a recognizable protocol and compare it with an appropriate treatment. Comparing an intensive, well supervised intervention with a waiting list answers a different question from comparing it with CBT of equal intensity and quality. Conclusions about efficacy should therefore always specify the type of comparator.

In research, ACT is often classified among contextual behavioral or “third wave” therapies, but this historical label does not represent a hierarchy of efficacy. Speaking of successive generations describes the development of models and techniques; it does not demonstrate that newer approaches are superior to earlier ones. Clinical comparison must therefore be based on specific trials and meta analyses, not on the chronological position of a treatment in the history of psychotherapy.

Processes may also overlap without being identical. Decentering, exposure to emotions, increased meaningful activity and attention to behavior are present, with different rationales, in several psychotherapies. This makes the presence of both common and specific mechanisms plausible and helps explain why theoretically different protocols may achieve similar average outcomes. For the patient, it is more useful to know the goals, procedures, evidence and commitment required than to frame schools of therapy as rigidly opposed.

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