Negative findings are helpful in in program development but they can be overlooked in the at time overwhelming flow of ACT data. That is why it is often recommended in the various sections on ACT research evidence on the website to prioritize well done meta-analysis and reviews by high quality scientific agencies; it's very hard nowadays for any one person to pick through thousands of studies to find negative findings. The list below is meant more as a set of examples. Readers can help by sending items they have stumbled across in the Randomized Controlled Trials list or elsewhere to missingstudies at gmail dot com (the email address is written like that to avoid spam). If you have them organized by topic and you are an ACBS member who has logged in you can easily add a daughter page below and describe the study or list of studies. If you have actual data about the population or treatment characteristics that predict poor response, that would be especially important. We know moderation is key and there is no "one size fits all" solution so finding you when ACT is less effective and when it is not is key to our progress. Thus it is good to list ideas about why it might not have worked, but do also consider that the other alternative is that it did not work because it does not work! It is especially important if the process moved significantly but the outcome did not. That is a model failure and it is a type of failure that demands careful attention. If the process did not move, or the outcome did not move, or both, it could be a technology failure or an interaction with other features and so on so. In either case, it needs to be pursued and this list is thus a resource for progress. In general below we are trying to emphasize studies where the primary outcome was moved significantly less by ACT than other methods -- mere mixed finding are quite common as any good meta-analysis will reveal but if it is unclear (e.g.. the primary outcome is not spelled out) those too can be included here. We hope this helps you find the times and places where ACT is second best or maybe even downright unhelpful.

Studies with negative findings or mixed findings (note, this is not a comprehensive list! See above):

• Ehlis, A.-C., Aas, B., Kieckhäfer, C., Schiepek, G., Rosenbaum, D., Theisen, C., Fallgatter, A. J., & Goldbeck, F. (2025). Move, connect and go outside! A randomized controlled trial of two online interventions and analysis of helpful coping strategies in COVID-19 “homestayers”. Applied Psychology: Health and Well-Being, 17(1), e12603. DOI: 10.1111/aphw.12603 The ACT group showed no significant changes over time.
• Hajati, E., Gharraee, B., Fathali Lavasani, F., Farahani, H., & Rajab, A. (2024). Comparing the effectiveness of acceptance-based emotion regulation therapy and acceptance and commitment therapy on hemoglobin glycosylated and self-care in patients with type II diabetes: A randomized controlled trial. Journal of behavioral medicine, 47(5), 874–885. DOI: 10.1007/s10865-024-00507-0 Both acceptance-based emotion regulation therapy (ABERT) and ACT led to significant improvements compared to the control group. However, ABERT was more effective than ACT in reducing HbA1c levels and enhancing self-care behaviors.
• Rauwenhoff, J.C.C., Bol, Y., Peeters, F., et al. (2024). Acceptance and commitment therapy for people with depressive and anxiety symptoms following acquired brain injury: Results of the BrainACT randomized controlled trial. Journal of Psychosomatic Research, 187, 111933. DOI: 10.1016/j.jpsychores.2024.111933 The study was negative on the primary outcome measures. On an individual level, this study showed that especially on the long term ACT seems to show a more clinically relevant decrease in anxiety and depressive symptoms compared to an active control intervention.
• Van Wasshenova, E., Boardley, D., Geers, A., Tull, M. & Steiner, V. (2023) A Brief Value-based Randomized Intervention to Promote Physical Activity in Patients Attending Cardiac Rehabilitation. American Journal of Health Education, 54(1), 10-19, DOI: 10.1080/19325037.2022.2142334 The results indicate that the intervention did not change positive affective associations or increase physical activity behavior.
• Hansen, K.E., Brandsborg, B., Kesmodel, U.S. et al. (2023). Psychological interventions improve quality of life despite persistent pain in endometriosis: results of a 3-armed randomized controlled trial. Quality of Life Research, 32, 1727–1744. DOI: 10.1007/s11136-023-03346-9 Compared to WL, psychological intervention (MY-ENDO + Non-specific) did not significantly reduce pain. However, psychological intervention did significantly improve three QoL-subscales as well as the endometriosis-related symptoms ‘dyschezia’ and ‘constipation’.
• Behnamfar, K., Rajaei, A., Teymouri, S. (2023). Comparing the effectiveness of cognitive-behavioral therapy and acceptance and commitment therapy on resilience of mothers with autistic children. Razavi International Journal of Medicine, 11(1), 38-45. DOI: 10.30483/rijm.2023.254412.1234 The results confirmed that CBT is more effective than ACT on the resilience of the mothers of children with autism. It is suggested that CBT be used to promote the mental well-being of these mothers.
• Myin-Germeys, I., van Aubel, E., Vaessen, T., Steinhart, H., Klippel, A., Lafit, G., Viechtbauer, W., Batink, T., van Winkel, R., van der Gaag, M., van Amelsvoort, T., Marcelis, M., Schirmbeck, F., de Haan, L., & Reininghaus, U. (2022). Efficacy of Acceptance and Commitment Therapy in Daily Life in Early Psychosis: Results from the Multi-Center INTERACT Randomized Controlled Trial. Psychotherapy and Psychosomatics, 91, 411–423. DOI: 10.1159/000522274 INTERACT did not support a significant effect of ACT-DL over TAU on the primary outcome measure of psychotic distress.
• Mueller, J., Richards, R., Jones, R. A., Whittle, F., Woolston, J., Stubbings, M., Sharp, S. J., Griffin, S. J., Bostock, J., Hughes, C. A., Hill, A. J., & Ahern, A. L. (2022). Supporting Weight Management during COVID-19 (SWiM-C): A randomised controlled trial of a web-based, ACT-based, guided self-help intervention. Obesity Facts, 15(4), 550–559. DOI: 10.1159/000524031 Differences in weight and some other outcomes were compatible with no effect of the intervention.
• Levin, M. E., Krafft, J., Seifert, S. & Lillis, J. (2022). Tracking valued and avoidant functions with health behaviors: A randomized controlled trial of the acceptance and commitment therapy matrix mobile app. Behavior Modification, 46(1), 63–89. DOI: 10.1177/0145445520913987 Neither the HBT or HBT+ACT app improved other health behavior outcome measures or values processes relative to the waitlist. Overall, findings suggest some benefits of the ACT Matrix app for addressing physical activity by tracking valued/avoidant functions, but mixed findings on acceptability, outcomes, and processes of change suggests impact may be relatively limited.
• Braun, L., Terhorst, Y., Titzler, I., Freund, J., Thielecke, J., Ebert, D.D., & Baumeister, H. (2022). Lessons learned from an attempted pragmatic randomized controlled trial for improvement of chronic pain-sssociated disability in green professions: Long-term effectiveness of guided online-based Acceptance and Commitment Therapy (PACT-A). International Journal of Environmental Research and Public Health, 19(21), 13858. DOI: 10.3390/ijerph192113858 No treatment effect for reduction of pain interference was found.
• Kianpour Barjoee, L., Amini, N., Keykhosrovani, M., & Shafiabadi, A. (2022). The Effect of Positive Thinking Skills Training and Acceptance and Commitment Therapy on Perceived Stress among Women with Breast Cancer. Women’s Health Bulletin, 9(1), 9-16. DOI: 10.30476/whb.2022.93905.1159 According to the results, positive thinking training and ACT were effective in reducing perceived stress in women with breast cancer. Moreover, positive thinking training was more effective in declining stress in women with breast cancer.
• Ebrahimi, A., Nasre Esfahan, E., Akuchekian, S., Izadi, R., Shaneh, E., & Mahaki, B. (2022). A randomized clinical trial: Comparison of group acceptance and commitment therapy with drug on quality of life and depression in patients with obsessive–compulsive disorder. Journal of Research in Medical Scienes, 27(1), 9. SSRIs are more effective than ACT in treating depression in obsessive–compulsive patients.
• Behnamfar, K., Rajaei, A.R., & Teymouri, S. (2022). Comparison of cognitive-behavioral therapy and acceptance and commitment therapy on cognitive flexibility in mothers with autistic children. Social Determinants of Health, 8(1), 1-9. DOI: 10.22037/sdh.v8i1.37302 The results indicated that both training methods of CBT and ACT significantly increased the cognitive flexibility of the mothers with autistic children. Based on the results of Tukey's test, CBT training was more effective on cognitive flexibility of the mothers with autistic children compared to ACT training.
• Faghihi, A., Zanjani, Z., Omidi, A. & Fakharian, E. (2022). A comparison of cognitive behavioral therapy and acceptance and commitment therapy received by patients with major depressive disorder following traumatic brain injury for emotional status and quality of life of their caregivers: A randomized controlled trial. Asian Journal of Social Health and Behavior, 5(1), 24-32. DOI: 10.4103/shb.shb_19_22 CBT is more effective than ACT.
• Laula, T. (2022). Psykologisk utvärdering av Acceptance and Commitment Therapy vid diabetes typ 2 : En behandlingsstudie med SCED-design inom primärvård. Dissertation, Mittuniversitetet, Sweden. The conclusion the author makes is that the present study as well as previous studies does not support the continued use of this treatment without further studies of its efficacy. Retrieved from https://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-45625
• De Wit, J., Beelen, A., Drossaert, C. H. C., Kolijn, R., Van Den Berg, L. H., Schröder, C. C., & Visser-Meily, J. M. A. (2020). Blended psychosocial support for partners of patients with ALS and PMA: Results of a randomized controlled trial. Amyotrophic Lateral Sclerosis And Frontotemporal Degeneration, 21, 344-354. DOI: 10.1080/21678421.2020.1757114 The support program had no effect on the primary or secondary outcomes, despite a significant positive effect on the intervening variable self-efficacy with regard to control over thoughts.
• Sabouri, H., Zarei, E., Samavi, A., & Amir Fakhraei, A. (2020). Comparison the effectiveness of Acceptance and Commitment Therapy and Compassion Focused Therapy on the quality of life and tendency to betray in married students with tendency to infidelity. Iranian Evolutionary and Educational Psychology, 2(3),184-199. DOI:10.29252/ieepj.2.3.184  CFT was more effective than ACT in terms of physical health and, conversely, ACT was more effective than CFT in terms of mental health and social communication.
• Rahimi, A., Amiri, H., Afsharriniya, K., & Arefi, M. (2020). Comparing the Effectiveness of Cognitive Behavioral Therapy (CBT) with Acceptance and Commitment Therapy (ACT) in the Enhancement of Marital Satisfaction and Sexual Intimacy in Couples Referred to Counseling Centers. Avicenna Journal of Neuro Psycho Physiology, 7(2), 126-132. DOI: 10.32592/ajnpp.2020.7.2.107 It was found that CBT exerted a more profound effect on marital satisfaction and sexual intimacy, compared to ACT.
• Levin, M.E., Hayes, S.C., Pistorello, J. & Seeley, J. (2016). Web-based self-help for preventing mental health problems in universities: Comparing acceptance and commitment training to mental health education. Journal of Clinical Psychology, 72, 207-225. doi: 10.1002/jclp.22254.
• Herbert, J. D., Forman, E. M., Kaye, J. L., Gershkovich, M., Goetter, E., Yuen, E. K., Glassman, L., Goldstein, S., Hitchcock, P., Tronieri, J. S., Berkowitz, S., & Marando-Blanck, S. (2018). Randomized controlled trial of acceptance and commitment therapy versus traditional cognitive behavior therapy for social anxiety disorder: Symptomatic and behavioral outcomes. Journal of Contextual Behavioral Science, 9, 88-96. DOI: 10.1016/j.jcbs.2018.07.008  Those who received CBT evidenced greater improvements in self-reported social anxiety symptoms and overall functioning than those who received ACT. Medium effect sizes, while not statistically significant, indicate that ACT participants may have had greater improvements in observer-rated social behavior than CBT participants.
• Montazeri, S., Aghaei Jashoghani, A., & Golparvar, M. (2018). Comparison of the Effectiveness of Cognitive-Behavioral Management Based on Mindfulness and Treatment Based on Acceptance and Commitment on Psychological Well-being in Multiple Sclerosis Patients. Sadra Medical Journal, 7(1), 59-74. DOI: 10.30476/smsj.2018.44755 The results of Bonferroni's post hoc test for the comparison of couples in groups showed that cognitive-behavioral management stress based on mindfulness rather than the one based on acceptance and commitment has had a greater impact on both post-test and follow-up on the total score of psychological well-being and autonomy components, environmental mastery, purposeful life, and personal growth.
• Masjedi-Araani, A., & Khanaliloo, R. (2018). Comparison of the Efficacy of Cognitive-Behavioral Therapy (CBT) and ACT (ACT) in Reducing Depression in Women with Multiple Sclerosis (MS). The International Journal of Body, Mind and Culture, 5(2), 112-121. DOI: 10.22122/ijbmc.v5i2.117 CBT was more effective than ACT.
• Jung, M. J., Na, M. O., & Son, C. N. (2017). Effects of Acceptance and Commitment Therapy (ACT) on premenstrual symptoms, attitudes about menstruation, and perceived stress of women with premenstrual syndrome. Journal of Digital Convergence, 15(1), 485-495. DOI : 10.14400/JDC.2017.15.1.485 In regards to attitudes toward menstruation, there were no statistical significance in the acceptance and commitment therapy (ACT) group
• Ko, Y-J., & Kim, J. M. (2015). The effect of cognitive behavioral therapy and acceptance and commitment therapy on female university students with social anxiety disorder. Korean Journal of Emotional & Behavioral Disorders, 31(2), 175-197. In the case of the ACT group, emotional characteristics and social interaction anxiety did not show significant changes.
• Craske, M. G., Niles, A. N., Burklund, L. J., Wolitzky-Taylor, K. B., Vilardaga, J. C. P., Arch, J. J., Saxbe, D. E., & Lieberman, M. D. (2014). Randomized controlled trial of cognitive behavioral therapy and acceptance and commitment therapy for social phobia: Outcomes and moderators. Journal of Consulting and Clinical Psychology, 82(6), 1034–1048. DOI: 10.1037/a0037212 Equivalent findings overall for ACT and CBT but better findings for CBT with participants with lower self-reported psychological flexibility at baseline and either very low or very high self-reported fear of negative evaluation.
• Luciano, J. V., Gullar, J. A., Aguado, J., López-del-Hoyo, Y., Olivan, B., Magallón, R., Alda, M., Serrano-Blanco, A., Gilli, M., & Garcia-Campayo, J. (2014). Effectiveness of group acceptance and commitment therapy for fibromyalgia: A 6-month randomized controlled trial (EFFIGACT study). Pain, 155, 693-702. DOI: 10.1016/j.pain.2013.12.029 Group based ACT was statistically superior to both recommended pharmacological treatment and waitlist immediately after treatment, and improvements were maintained at 6 months with medium effect sizes in most cases. Unexpectedly, 4 of the 5 tested path analyses did not show a mediation effect.
• Lanza, P. V., García, P. F., Lamelas, F. R., & González-Menéndez, A. (2014). Acceptance and commitment therapy versus cognitive behavioural therapy in the treatment of substance use disorder with incarcerated women. Journal of Clinical Psychology, 70, 644-657. DOI: 10.1002/jclp.22060 At posttreatment, CBT was more effective than ACT in reducing anxiety sensitivity.
• Forman, E. M., Shaw, J. A., Goetter, E. M., Herbert, J. D., Park, J. A., & Yuen, E. K. (2012). Long-term follow-up of a randomized controlled trial comparing Acceptance and Commitment Therapy and standard Cognitive Behavior Therapy for anxiety and depression. Behavior Therapy, 43, 801-811. DOI: 10.1016/j.beth.2012.04.004 Treatment gains were better maintained at follow-up in the CT condition.