Third-Wave CBT: ACT, DBT, MBCT & Beyond

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Term

ACT (Acceptance and Commitment Therapy)

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Definition

A third-wave CBT developed by Steven Hayes and colleagues, grounded in Relational Frame Theory. Rather than challenging thought content, ACT builds psychological flexibility through six core processes: acceptance, cognitive defusion, present-moment awareness, self-as-context, values, and committed action — organised in the hexaflex model.

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All 6 Terms & Definitions

ACT (Acceptance and Commitment Therapy)
A third-wave CBT developed by Steven Hayes and colleagues, grounded in Relational Frame Theory. Rather than challenging thought content, ACT builds psychological flexibility through six core processes: acceptance, cognitive defusion, present-moment awareness, self-as-context, values, and committed action — organised in the hexaflex model.
Psychological Flexibility
ACT's central therapeutic target: the ability to contact the present moment fully and change or persist in behaviour when doing so serves one's chosen values. Its opposite — psychological inflexibility, driven by experiential avoidance and cognitive fusion — is ACT's transdiagnostic model of psychopathology.
Cognitive Defusion
An ACT process of stepping back from thoughts and seeing them as mental events rather than literal truths. Techniques include prefixing thoughts with "I notice I am having the thought that…", repeating a word until it loses meaning, and observing thoughts on leaves floating downstream.
Experiential Avoidance
The tendency to suppress, escape, or alter unwanted private events — thoughts, feelings, sensations — even when doing so causes long-term harm. Proposed by Hayes et al. (1996) as a transdiagnostic mechanism; the primary behavioural target of ACT.
DBT (Dialectical Behaviour Therapy)
Developed by Marsha Linehan for borderline personality disorder. Combines CBT with Zen mindfulness, organising skills into four modules: mindfulness, distress tolerance, emotion regulation, and interpersonal effectiveness. The "dialectic" balances acceptance (you are doing the best you can) and change (you need to do better).
MBCT (Mindfulness-Based Cognitive Therapy)
Developed by Segal, Williams & Teasdale (2002) to prevent depressive relapse. Combines mindfulness meditation with cognitive therapy to help patients recognise early warning signs of depression and respond with mindful awareness rather than rumination. NICE-recommended (NG222) for relapse prevention in patients who have recovered from depression and have a history of ≥3 previous depressive episodes.