Acceptance and Commitment Therapy (ACT): Independent Evidence

Table of contents

• Evidence summary
• What ACT is
• How it works: the psychological flexibility model
• What works and what does not
• Benefits by claim
• How good is the research? The Öst debate and researcher allegiance
• Risks and limits
• Who ACT may not suit
• How it is delivered: formats, NHS access and cost
• Follow the money: who makes it and who funded the evidence
• Related research
• Frequently asked questions
• Sources and funding notes

Evidence summary

Independent evidence and credibility scorecard

Independence tiers: 1 = regulator or government body; 2 = academic or Cochrane team with no declared commercial funding for the work; 3 = independent authors analysing mostly manufacturer-run trials, or minor declared industry ties; 4 = manufacturer-funded or manufacturer-authored. Credibility runs from A (highest) to D. In this article, because ACT has no manufacturer, tier 3 also covers reviews published in the ACT society's own journal, reviews whose funding statement we could not access, and trials co-authored by the organisation that developed the programme being tested; tier 4 covers work authored by ACT's originator or by people who declare income from ACT books, courses or workshops.

Sources cluster in the UK, the US, northern Europe and Australia. The WHO trials add evidence from Uganda, Turkey and Indonesia, which is unusual for a talking therapy.

What ACT is

Acceptance and commitment therapy (ACT) is a behavioural talking therapy. Cochrane reviewers group it with the "third wave" cognitive and behavioural therapies, alongside approaches such as mindfulness-based cognitive therapy and compassion-focused work (Churchill et al. 2013). Where traditional CBT often teaches people to test and change unhelpful thoughts, ACT teaches them to notice thoughts and feelings without being pushed around by them, and to keep doing things that matter to them.

• Origins: It was developed in the US by Steven C. Hayes, Kirk Strosahl and Kelly Wilson. Their first ACT book appeared in 1999 (Hayes et al. 1999, cited in Turrini et al. 2022). The first ACT study appeared in 1986 (Gloster et al. 2020). Hayes was based at the University of Nevada, Reno (Hayes et al. 2006).
• Scale of research: ACBS reports more than 1,450 randomised trials and more than 600 reviews of various kinds as of early 2026 (ACBS evidence page). Trial count is not the same as trial quality.
• Who owns it: Nobody. ACT is a method, not a product, and it has no licence holder. ACBS states that "there is no ACT certification process", by choice (ACBS).
• Regulation: No medicines regulator approves talking therapies. In the UK, titles such as "clinical psychologist" and "counselling psychologist" are protected by law and require registration with the Health and Care Professions Council (HCPC). The NHS advises checking that a private therapist belongs to a register accredited by the Professional Standards Authority (NHS). "ACT therapist" is not a protected title.
• Related brands: WHO's Doing What Matters in Times of Stress self-help guide and its group course Self-Help Plus (SH+) are both based on ACT (WHO 2026; Purgato et al. 2021).

How it works: the psychological flexibility model

ACT's central idea is "psychological flexibility": staying in contact with the present moment, including unpleasant thoughts and feelings, while choosing actions that serve one's values. ACBS describes six core processes (ACBS):

1. Acceptance: actively making room for unwanted feelings, rather than spending effort trying to remove them.
2. Cognitive defusion: learning to see thoughts as thoughts, not as literal truths or commands.
3. Being present: non-judgemental attention to what is happening now.
4. Self as context: a sense of self as the observer of experiences, rather than being defined by them.
5. Values: clarifying the qualities a person wants their actions to reflect.
6. Committed action: building patterns of behaviour linked to those values.

The theory holds that much distress is kept going by attempts to avoid or control painful inner experiences. ACT is linked to a laboratory research programme on language and cognition called Relational Frame Theory. Its developers wrote in 2006 that the supporting evidence was "broadly supportive" but that the literature was "not mature" (Hayes et al. 2006).

What mediation studies show

If ACT works the way its theory says, changes in psychological flexibility should come before, and explain, changes in symptoms. The evidence for this is suggestive, not proven:

• Supportive but low quality: A systematic review of 12 mediation studies published from 2006 to 2015 found results "generally consistent" with the model. The studies were limited in quality and focused on only a few processes (Stockton et al. 2019).
• In a large field trial: In the WHO trial with South Sudanese refugee women, flexibility scores statistically mediated the fall in distress (Lakin et al. 2023).
• Not always: In a meta-analysis of workplace ACT for healthcare staff, psychological flexibility did not improve significantly more in ACT groups than in controls, even though distress did (Prudenzi et al. 2021).
• A measurement problem: Most of these studies use the Acceptance and Action Questionnaire (AAQ-II). An independent factor analysis found its items related more strongly to distress than to acceptance (Wolgast 2014). If the scale partly measures distress, then "flexibility mediates distress" risks being circular.

Bottom line: it is proven that people improve with ACT. It is not yet proven that they improve because of the six processes rather than the shared ingredients of most good therapy, such as a credible rationale, a supportive therapist, and behavioural practice between sessions.

What works and what does not

Benefits by claim

Depression

The evidence for depression is consistent in direction but modest in quality.

• Cochrane (2013): Comparing third-wave therapies with usual care, reviewers found 4 small studies (224 people). Results favoured the third-wave therapies on clinical response, but the evidence was "very low quality". None used independent outcome assessors, and "evidence suggested researcher allegiance" (Churchill et al. 2013). Against other psychological therapies, two small early ACT trials (56 people) showed no difference from CBT (Hunot et al. 2013).
• Newer pooled data: A 2025 meta-analysis in people diagnosed with depression found ACT reduced depressive symptoms (SMD −0.69, 95% CI −1.06 to −0.32; low certainty) (Kong et al. 2025). An SMD of about 0.7 would be a medium-to-large effect, but "low certainty" means the true effect could be quite different.
• The largest analysis: A 2026 meta-analysis of 263 studies (21,830 participants) found a large effect against waiting lists for depression-focused ACT (g 1.10); its comparison with active treatments could not be checked (Borgogna et al. 2026).
• Guidelines: The US VA/DoD guideline lists ACT among seven psychotherapies it suggests for major depression, as a "weak for" recommendation, not ranked (VA/DoD 2022). NICE's 2022 depression guideline does not list ACT among its treatment options (NICE NG222).

Anxiety disorders

The best head-to-head trial randomised 128 adults with mixed anxiety disorders to ACT or CBT. Both treatments included exposure. Both groups improved similarly by the end of treatment. At 12 months the groups diverged on some measures: ACT scored higher on psychological acceptance and CBT on quality of life (Arch et al. 2012). Its funding statement was not re-checked here.

A cumulative meta-analysis concluded there is "insufficient evidence" that ACT for anxiety is efficacious against active control conditions (Hacker et al. 2016). The critical Öst review rated ACT "possibly efficacious" for mixed anxiety (Öst 2014). NICE's guideline for generalised anxiety and panic disorder does not mention ACT (NICE CG113).

Chronic pain

This is where ACT has its strongest institutional backing, and where the gap between guideline confidence and Cochrane caution is most visible.

• NICE (UK): "Consider acceptance and commitment therapy (ACT) or cognitive behavioural therapy (CBT) for pain" for people aged 16 and over with chronic primary pain, delivered by trained healthcare professionals (NG193, 1.2.3). The committee found ACT improved quality of life and sleep and reduced pain and distress, but the evidence came from "a fairly small number of studies". One economic evaluation found ACT cost effective, and there was no reason to prefer ACT over CBT or vice versa (NG193 rationale).
• Cochrane (2020): 5 ACT studies. Against active controls there was no clear difference for most outcomes at the end of treatment. The evidence was rated mostly low or very low quality (Williams et al. 2020).

What this means: ACT for pain mainly aims to help people live better despite pain. It is more likely to improve daily functioning and mood than to reduce pain scores. That matches its stated goals, but it is worth knowing before starting.

Psychosis

A frequently cited early trial randomised 80 inpatients with psychotic symptoms to 4 sessions of ACT plus usual care, or usual care alone. Four months after discharge, the ACT group was less likely to be rehospitalised. Symptom frequency did not differ between groups, but they rated their delusions and voices as less believable (Bach & Hayes 2002). The trial was small and co-authored by ACT's originator.

A 2020 meta-analysis pooled 16 RCTs (1,268 people) of acceptance- and mindfulness-based therapies combined. It found moderate-to-large effects on overall symptoms (SMD 0.80) and hospitalisation, small effects on negative symptoms, and no significant effect on positive symptoms such as hallucinations (Jansen et al. 2020). An earlier review of 8 RCTs (434 patients), 4 of them acceptance-based, found moderate evidence for short-term benefits and no serious adverse events (Cramer et al. 2016). NICE recommends CBT and family intervention for psychosis and does not mention ACT (NICE CG178).

Stress at work and burnout

A meta-analysis of 10 RCTs in healthcare professionals found ACT reduced general distress (g 0.39, 95% CI 0.04 to 0.75) and work-related distress at follow-up (g 0.30). The authors judged study quality "poor" (Prudenzi et al. 2021). A review of 14 controlled trials on staff burnout found mostly positive results but small samples and loosely defined interventions (Towey-Swift et al. 2023). A 2026 review of 11 online workplace ACT trials found "modest but significant" improvements; workload and time pressure often limited participation (Lampinen et al. 2026). Öst rated ACT "possibly efficacious" for stress at work (Öst 2014).

Stress in hard times: WHO's Doing What Matters and Self-Help Plus

The WHO published Doing What Matters in Times of Stress in April 2020 as a free illustrated guide with audio exercises, available in many languages (WHO). The WHO describes it as "based on acceptance and commitment therapy" (WHO 2026). Its group version, Self-Help Plus, is a 5-session course for up to 30 people, led by non-specialist facilitators using pre-recorded audio (WHO SH+). Its randomised trials give a mixed but informative picture:

• Uganda: Almost 700 South Sudanese refugee women. Distress fell more with Self-Help Plus, and the benefit was still present at 3 months. Funded by the Research for Health in Humanitarian Crises (R2HC) programme, managed by Elrha; no competing interests declared (Tol et al. 2020; full text).
• Turkey: 642 distressed Syrian refugees without a mental disorder. At 6 months, 21.7% of the Self-Help Plus group had a mental disorder vs 40.7% of controls (RR 0.53, 95% CI 0.41 to 0.70). There was no benefit immediately after the course (Acarturk et al. 2022). A linked economic evaluation estimated about US$1,147 per quality-adjusted life year gained when the course was run in groups of 10 (Park et al. 2022).
• Western Europe: Refugees and asylum seekers in 5 countries. Fewer disorders straight after the course (RR 0.50, 95% CI 0.29 to 0.87), but no preventive effect at 6 months, the primary outcome (Purgato et al. 2021). The 12-month follow-up reported improvements in distress, depression and wellbeing (Turrini et al. 2022). The European trials were funded by the European Commission (grant 779255, "RE-DEFINE") (protocol).
• Indonesia (individual version): 303 Afghan refugees received the guide with weekly phone support or repeated assessments only. Distress fell more with the guide (d 0.56 after treatment; d 0.45 at 1 month), and no serious adverse events were reported. Funded by the Australian Research Council and Australian NHMRC (Nickerson et al. 2026; full text).

The WHO's Self-Help Plus page states that the course "has been shown to reduce psychological distress and prevent the onset of mental disorders" (WHO SH+). The distress claim is supported. The prevention claim rests on one positive trial (Turkey) and one negative trial (Western Europe).

Self-help books, apps and online ACT

A meta-analysis of 13 self-help ACT studies (2,580 participants) found small benefits for depression (g 0.34, 95% CI 0.07 to 0.61) and anxiety (g 0.35, 95% CI 0.09 to 0.60). The authors called their conclusions "tentative" and found that clinician guidance improved results (French et al. 2017). A review of 25 internet-based ACT trials found small effects that lasted to follow-up. Therapist-guided programmes did better, and there was "limited evidence of reliable, clinically significant effects" (Thompson et al. 2021). For chronic pain, a Cochrane review of remotely delivered therapy found only 7 ACT trials, mostly low or very low certainty (Rosser et al. 2023).

Living with serious physical illness

The strongest single trial of ACT is not in mental health at all. The UK COMMEND trial randomised 191 people with motor neuron disease to up to 8 sessions of adapted ACT plus usual care, or usual care alone. Quality of life was better with ACT at 6 months, and the trial reported clinically meaningful gains at 6 and 9 months. Of 75 adverse events, none was judged to be linked to the therapy. It was funded by the NIHR and the MND Association (Gould et al. 2024).

How good is the research? The Öst debate and researcher allegiance

The most important public dispute about ACT is between a critical meta-analysis and ACT researchers' response to it. We present both sides.

The critique: Öst (2014)

Swedish psychologist Lars-Göran Öst analysed 60 RCTs (4,234 participants). The average effect across all comparisons was small (0.42), down from 0.68 in his 2008 review, with "no significant improvement in methodological quality". Against cognitive or behavioural treatments the effect was 0.16 and not significant. He concluded that ACT was "not yet well-established for any disorder": "probably efficacious" for chronic pain and tinnitus, and "possibly efficacious" for depression, psychotic symptoms, OCD, mixed anxiety, drug abuse and stress at work (Öst 2014).

The rebuttal: Atkins et al. (2017)

Ten authors, including ACT's originator Steven Hayes, re-examined the review. They reported 91 factual or interpretive errors affecting 80% of the studies reviewed. They found that Öst's quality ratings did not match those of independent rating teams, and that the errors were "dominantly more negative toward ACT". They argued the review "should be set aside" and called for reviews by diverse teams with shared raw data (Atkins et al. 2017).

The reply: Öst (2017)

Öst rejected each point. He said his ratings were reliable (Öst 2017).

Our reading

• The headline numbers agree. Öst and Gloster both found that ACT beats inactive controls and does not clearly beat CBT (Öst; A-Tjak; Gloster). The dispute is mostly about how to label the evidence, not what it shows.
• Both sides have allegiances. Öst co-authors trials of exposure-based CBT, such as one-session treatment for phobias (Ollendick et al. 2009). The rebuttal was co-authored by ACT's originator and by researchers who run ACT trials.
• Allegiance is a measurable bias. An overview of 30 meta-analyses found a moderate link between researcher allegiance and reported outcomes in psychotherapy trials (r = 0.26) (Munder et al. 2013). Cochrane reviewers specifically flagged allegiance in early ACT depression trials (Hunot et al. 2013).
• The cleanest tests are recent and publicly funded (COMMEND, the WHO trials, Arch 2012). They show real but mostly modest benefits, plus one clear null result.

Risks and limits

ACT has no drug side effects, and no specific harms have been established. But "no harms found" is not the same as "no harms", because few trials looked.

Where trials did monitor safety, they found nothing attributable to ACT. In COMMEND, 75 adverse events were recorded, 38 of them serious, and none was judged linked to ACT (Gould et al. 2024).

Engagement is a practical limit. Participants completed about three-quarters of online ACT programmes on average (Thompson et al. 2021).

Who ACT may not suit

• People in crisis or at immediate risk: They need urgent assessment and crisis care first (see the crisis numbers above).
• People with PTSD: NICE's first-line options are trauma-focused CBT and EMDR (NICE NG116).
• People with psychosis: ACT has only been tested as an add-on to usual care, not as a replacement for medication, CBT for psychosis or family intervention (Jansen et al. 2020; NICE CG178).
• People with pain from a known, treatable cause: NICE's ACT recommendation covers chronic primary pain in people aged 16 and over (NG193). Pain from conditions such as arthritis has separate guidance.
• Young people: A 2025 meta-analysis of 65 studies in 15- to 25-year-olds found a moderate effect (g 0.72) but rated the evidence very low quality. ACT matched, but did not beat, CBT (Keulen et al. 2025).
• People who want a treatment NICE recommends first for depression or anxiety: NHS services usually offer guided self-help, CBT, counselling, interpersonal therapy or other listed options (NHS).

How it is delivered: formats, NHS access and cost

Formats and length

ACT has been tested in very different "doses". Examples from trials: 4 sessions for psychiatric inpatients (Bach & Hayes 2002); up to 8 individual sessions in COMMEND (Gould 2024); a five-session group course with pre-recorded audio in Self-Help Plus (Tol 2020); 5 weeks of a self-help guide with weekly phone calls (Nickerson 2026); and self-help books read over 2 months (Jeffcoat & Hayes 2012). It is also delivered in groups, online and through apps.

Availability on the NHS

• Pain services: NICE recommends considering ACT for chronic primary pain and notes it "is also used to varying degrees in practice" (NG193). Availability therefore depends on the local pain service.
• Anxiety and depression: The NHS website's list of talking therapies for anxiety and depression does not include ACT. It lists guided self-help, CBT, counselling, interpersonal therapy, dynamic interpersonal therapy, couples therapy, EMDR and MBCT (NHS). Some therapists may still use ACT techniques within these services.
• Free WHO materials: Doing What Matters in Times of Stress can be downloaded free from the WHO (WHO).

United States

The Veterans Health Administration runs a national ACT-for-depression training programme; 334 therapists completed it in the cohorts reported (Walser et al. 2013). The VA/DoD guideline lists ACT as a suggested psychotherapy for depression (VA/DoD 2022).

Cost

NICE notes that costs "can vary" with the number and length of sessions, group or individual format, online or face-to-face delivery, and who runs it (NG193). Adults registered with a GP can usually refer themselves to NHS talking therapies for anxiety and depression without seeing a GP (NHS). We did not find an authoritative source for typical private fees. If paying privately, check that the therapist is on a register accredited by the Professional Standards Authority, and ask about their ACT training and supervision, since no ACT certificate exists.

Combining ACT with medicines and other treatments

As a talking therapy, ACT has no drug interactions. In most trials it was added to usual care, including medication (Gould 2024; Bach & Hayes 2002). NICE's pain guideline lists ACT or CBT alongside exercise and, for some people, an antidepressant (NG193). Starting ACT is not a reason to stop prescribed treatment without talking to the prescriber.

Follow the money: who makes it and who funded the evidence

Who "makes" and sells ACT

No company owns ACT, and no drug company profits from it. The money around ACT comes from training, books, conferences, apps and professional reputation.

• The professional body: The Association for Contextual Behavioral Science (ACBS) describes itself as "an unincorporated association" organised for educational and scientific purposes and run as "a non-profit association" (ACBS bylaws). A separate ACBS Foundation in Jenison, Michigan (EIN 83-2620099) is listed as a 501(c)(3) public charity with a 2019 IRS ruling year (Charity Navigator). We could not find published accounts for ACBS itself.
• The journal: The reviews by Gloster et al. (2020) and French et al. (2017) appeared in the Journal of Contextual Behavioral Science, which is linked to the ACBS community. Publisher arrangements were not re-checked.
• Training: ACBS does not certify ACT therapists but runs a peer-review process for ACT trainers (ACBS). Steven Hayes's personal website sells books, online courses ("ACT Immersion"), in-person workshops (an "ACT BootCamp®" in October 2026) and a practitioner app (stevenchayes.com).
• Books: Hayes's self-help book Get Out of Your Mind and Into Your Life is published by New Harbinger Publications (US). It was reissued in September 2025 at US$24.95 in paperback. New Harbinger lists Context Press as an imprint and Praxis Continuing Education and Training as its subsidiary company (New Harbinger). In other words, the same group publishes ACT books and sells clinician training.
• Disclosures: A 2024 review co-written by Hayes lists, in its competing-interest statement, royalties from publishers and books, speaking fees and relationships with training companies (Hayes and King 2024). The 2020 umbrella review by Gloster et al. declares no competing interests and was funded by the Swiss National Science Foundation (Gloster 2020). We could not confirm a separate disclosure of workshop or app income for Gloster.
• Public provider: The WHO gives its ACT-based guide away free (WHO), and the research charity that funded the Uganda trial describes it as one of WHO's most downloaded publications (Elrha). Its interest is reputational and programmatic, not commercial.

Who funded the trials

• UK: NIHR Health Technology Assessment and the MND Association funded COMMEND (Gould 2024). NICE's guideline work is publicly funded.
• US: The funding of the main ACT-versus-CBT anxiety trial (Arch 2012).
• Europe and humanitarian funders: The European Commission funded the European and Turkish Self-Help Plus trials (grant 779255) (protocol; Turkey trial). The R2HC programme, managed by Elrha, funded the Uganda trial (Tol 2020). The Swiss National Science Foundation funded the 2020 umbrella review.
• Australia: The Australian Research Council and NHMRC funded the Indonesian Doing What Matters trial (Nickerson 2026).
• Developer-run trials: Many early trials were run at the developer's own university with the developer as co-author, often against usual care or a waitlist (for example, Bach & Hayes 2002; Muto, Hayes & Jeffcoat 2011; Jeffcoat & Hayes 2012). The funding statement for the 2002 psychosis trial was not confirmed here.

Documented integrity events

No medicines-style regulator oversees talking therapies, so there are no warning letters or recalls to report. In the sources we checked, we found no lawsuits or regulatory actions involving ACT itself; we did not search retraction databases exhaustively. The documented concerns are about research bias, not misconduct:

• Cochrane reviewers rated early ACT depression trials at high risk of researcher allegiance (Hunot 2013; Churchill 2013).
• The public Öst–Atkins dispute, with each side alleging errors by the other (Atkins 2017; Öst 2017).
• In internet-delivered depression interventions generally (not ACT alone), trials with industry sponsorship or researchers' financial conflicts reported larger effects (Munder et al. 2026). This matters for commercial ACT apps.

What this means: ACT's money trail looks different from a drug's. The large, recent, publicly funded trials (NIHR, NIMH, European Commission, humanitarian and Australian funders) support a real but mostly modest benefit, and one of them was clearly negative. The more glowing numbers come from small trials against waiting lists, many run by people who developed, teach or write books about ACT. The honest summary is that ACT is a legitimate option of similar value to CBT, not a superior one.

Related research

For wider, evidence-graded context, see these Pure City Research guides:

• Cognitive behavioural therapy (CBT): treatment evidence and safety
• Behavioural activation for depression
• Interpersonal therapy for depression
• Exposure and response prevention (ERP)
• Trauma-focused therapy
• Major depressive disorder
• Generalised anxiety disorder
• Occupational burnout
• Workplace mental health prevention
• Stress, anxiety and depression: evidence and care options
• Duloxetine and amitriptyline (medicines also used in chronic pain)
• Mental health crisis warning signs

Frequently asked questions

Sources and funding notes

What we could not verify: We re-checked the central numbers against abstracts and search summaries. Where a figure could not be confirmed, we removed it or reworded it. Still not re-checked: the full texts and funding statements of several paywalled reviews (Atkins et al. 2017, Öst's 2017 reply, A-Tjak et al. 2015, Hughes et al. 2017, Hacker et al. 2016, Jansen et al. 2020, Prudenzi et al. 2021, Thompson et al. 2021, Borgogna et al. 2026, Kong et al. 2025); the declarations of interest in the Cochrane reviews; the Tol et al. 2020 sample details and R2HC funding; the European Commission grant number for the Self-Help Plus trials (taken from the study protocols); the Jansen, Prudenzi, Towey-Swift, Lampinen, Keulen, Park and Nickerson figures; the NICE NG222 and CG113 omissions; the 2018 editor's note on the Öst–Atkins exchange; ACBS's own accounts and membership; Hayes's book, publisher and training details; and typical private UK fees for ACT. Removed as unverifiable: the NIH RePORTER counts, the Walser et al. 2013 outcomes, the APA Division 12 ratings and the Cochrane pain effect sizes. We did not review ACT for tinnitus, OCD, substance use or eating disorders in depth.

1. NICE NG193: Chronic pain (primary and secondary) in over 16s, recommendations (2021) — UK guideline; NICE, funded by the Department of Health and Social Care.
2. NICE NG193: Rationale and impact — evidence summary for ACT and cost notes; NICE.
3. NICE NG222: Depression in adults (2022) — UK guideline; ACT not listed; NICE.
4. NICE CG113: Generalised anxiety disorder and panic disorder — UK guideline; ACT not mentioned; NICE.
5. NICE CG178: Psychosis and schizophrenia in adults — UK guideline; recommends CBT and family intervention; NICE.
6. NICE NG116: Post-traumatic stress disorder — UK guideline; NICE.
7. VA/DoD Clinical Practice Guideline for the Management of Major Depressive Disorder, version 4.0 (2022) — US government guideline; recommendation 7 lists ACT.
8. Williams ACC et al. Psychological therapies for the management of chronic pain (excluding headache) in adults. Cochrane 2020 — UK; declarations not re-checked.
9. Rosser BA et al. Psychological therapies delivered remotely for chronic pain. Cochrane 2023 — UK; two authors declared institutional consultancy funding from Orion Pharma and/or Reckitt Benckiser, unrelated to the review.
10. Hunot V et al. 'Third wave' cognitive and behavioural therapies versus other psychological therapies for depression. Cochrane 2013 — University of Bristol; two authors specialise in CBT.
11. Churchill R et al. 'Third wave' cognitive and behavioural therapies versus treatment as usual for depression. Cochrane 2013 — University of Bristol; "None known".
12. Öst LG. The efficacy of Acceptance and Commitment Therapy: an updated systematic review and meta-analysis. Behav Res Ther 2014 — Sweden; funding statement not accessible.
13. Atkins PWB et al. Departing from the essential features of a high quality systematic review of psychotherapy: a response to Öst (2014). Behav Res Ther 2017 — Australia/US/Sweden; co-authored by ACT's originator; funding statement not accessible.
14. Öst LG. Rebuttal of Atkins et al. (2017) critique. Behav Res Ther 2017 — Sweden.
15. A-Tjak JG et al. A meta-analysis of the efficacy of acceptance and commitment therapy for clinically relevant mental and physical health problems. Psychother Psychosom 2015 — Netherlands/US; funding statement not accessible.
16. Gloster AT et al. The empirical status of acceptance and commitment therapy: a review of meta-analyses. J Contextual Behav Sci 2020 (doi) — Swiss National Science Foundation; "None" competing interests; ACBS journal.
17. Borgogna NC et al. A cross-cultural incremental effects meta-analysis of ACT for depression. Cogn Behav Ther 2026 — US-led; funding not accessible.
18. Kong Q et al. The efficacy of ACT for depression: a systematic review and meta-analysis. Psychiatry Res 2025 — China; no competing interests declared.
19. Arch JJ et al. Randomized clinical trial of CBT versus ACT for mixed anxiety disorders. J Consult Clin Psychol 2012 — US; funding statement not re-checked.
20. Hacker T et al. Acceptance and commitment therapy – do we know enough? J Affect Disord 2016 — Germany/UK; funding not accessible.
21. Hughes LS et al. ACT for chronic pain: a systematic review and meta-analyses. Clin J Pain 2017 — UK NHS/university authors; funding not accessible.
22. Bach P, Hayes SC. ACT to prevent the rehospitalization of psychotic patients. J Consult Clin Psychol 2002 — US; co-authored by ACT's originator.
23. Jansen JE et al. Acceptance- and mindfulness-based interventions for persons with psychosis. Schizophr Res 2020 — Denmark/Australia; funding not accessible.
24. Cramer H et al. Mindfulness- and acceptance-based interventions for psychosis. Glob Adv Health Med 2016 — Germany/Australia.
25. Prudenzi A et al. Group-based ACT interventions for healthcare professionals. J Affect Disord 2021 — UK; PubMed lists a UK Department of Health grant; one author affiliated with Fiona Day Consulting Ltd.
26. Towey-Swift KD et al. ACT for professional staff burnout. J Ment Health 2023 — UK/Norway.
27. Lampinen VS et al. Online ACT-based interventions in occupational contexts. Internet Interv 2026 — Finland; no conflicts declared.
28. French K et al. What is the evidence for the efficacy of self-help ACT? J Contextual Behav Sci 2017 — UK; ACBS journal; funding not seen.
29. Thompson EM et al. Internet-based ACT: a transdiagnostic meta-analysis. Behav Ther 2021 — Australia (Monash University); funding statement not accessible.
30. Keulen J et al. The efficacy of ACT for transitional-age youth. Clin Child Fam Psychol Rev 2025 — Netherlands; no conflicts declared.
31. Gould RL et al. ACT plus usual care for motor neuron disease (COMMEND). Lancet 2024 — UK; NIHR HTA 16/81/01 and MND Association.
32. Tol WA et al. Guided self-help to reduce psychological distress in South Sudanese female refugees in Uganda. Lancet Glob Health 2020 (full text) — R2HC programme, managed by Elrha; WHO staff co-authors; no competing interests.
33. Lakin DP et al. Psychological flexibility as a mechanism of change in Self-Help Plus. J Consult Clin Psychol 2023 — secondary analysis of the Uganda trial.
34. Purgato M et al. Effectiveness of Self-Help Plus in preventing mental disorders in refugees and asylum seekers in Western Europe. Psychother Psychosom 2021 (full text) — European Commission grant 779255; no conflicts.
35. Turrini G et al. Long-term effectiveness of Self-Help Plus: 12-month outcomes. Epidemiol Psychiatr Sci 2022 — European Commission grant 779255; conflicts "None".
36. Acarturk C et al. Effectiveness of a WHO self-help psychological intervention for preventing mental disorders among Syrian refugees in Turkey. World Psychiatry 2022 — European Commission grant 779255 (acknowledgements).
37. Purgato M et al. Self-Help Plus study protocols for two randomised controlled trials (Europe and Turkey). BMJ Open 2019 — European Commission grant 779255; "None declared".
38. Park AL et al. Cost-effectiveness of Self-Help Plus for adult Syrian refugees in Turkey. JAMA Netw Open 2022 — one author declared personal fees from HealthRight International, WHO and Johns Hopkins.
39. Nickerson A et al. Efficacy of a WHO guided self-help intervention for Afghan refugees. JMIR Ment Health 2026 (full text) — Australian Research Council LP230100426; NHMRC; MQ; no conflicts.
40. WHO. Doing What Matters in Times of Stress: an illustrated guide (2020) — WHO; free.
41. WHO. Self-Help Plus (SH+): a group-based stress management course for adults (2021) — WHO.
42. WHO news release, 1 June 2026: new guide to scale psychological self-help — WHO.
43. Elrha R2HC impact case study: Self-Help Plus — funder's own case study.
44. Stockton D et al. Mechanisms of change during ACT: a systematic review of mediation studies. Behav Cogn Psychother 2019 — UK/Chile; funding not accessible.
45. Wolgast M. What does the Acceptance and Action Questionnaire (AAQ-II) really measure? Behav Ther 2014 — Sweden.
46. Hayes SC et al. Acceptance and commitment therapy: model, processes and outcomes. Behav Res Ther 2006 — developers' own review.
47. Turrini G et al. 2022 (full text) — used for the 1999 ACT manual citation and the link between Self-Help Plus and Doing What Matters.
48. Muto T, Hayes SC, Jeffcoat T. ACT bibliotherapy for Japanese students. Behav Ther 2011 and Jeffcoat T, Hayes SC. ACT bibliotherapy for K-12 teachers and staff. Behav Res Ther 2012 — US; co-authored by ACT's originator.
49. Munder T et al. Researcher allegiance in psychotherapy outcome research: an overview of reviews. Clin Psychol Rev 2013 — Switzerland.
50. Munder T et al. Conflict of interest in trials of internet-based interventions for depression. Psychother Res 2026 — Germany/Switzerland.
51. Ollendick TH, Öst LG et al. One-session treatment of specific phobias in youth. J Consult Clin Psychol 2009 — used to document Öst's CBT research.
52. Hayes and King 2024, Journal of Contextual Behavioral Science (history of ACT and first 1,000 RCTs; competing-interest statement) — conflict-of-interest statement of Steven Hayes.
53. ACBS: State of the ACT evidence, The six core processes of ACT, Bylaws and ACT certification — ACT professional body (interested party).
54. Charity Navigator: Association for Contextual Behavioral Science Foundation — US charity listing (EIN 83-2620099).
55. Steven C. Hayes personal website — commercial offerings (books, courses, workshops, app).
56. New Harbinger Publications: Get Out of Your Mind and Into Your Life — publisher page; lists Praxis CET as a subsidiary.
57. NIH RePORTER — US government grants database (title search for "acceptance and commitment", 6 October 2026).
58. NHS: Talking therapies — NHS England public information.
59. Health and Care Professions Council: professions and protected titles — UK statutory regulator.

Educational research reviewed 6 October 2026. This article is not medical advice; talk to a qualified clinician or pharmacist before starting, stopping or combining treatments.