Monitoring Clinically Relevant Behaviors and Experiential Avoidance Throughout the Course of Acceptance and Commitment Therapy: A Single-Case Quasi-Experimental Study
Restricted accessResearch articleFirst published online July, 2025
Monitoring Clinically Relevant Behaviors and Experiential Avoidance Throughout the Course of Acceptance and Commitment Therapy: A Single-Case Quasi-Experimental Study
The present single-case quasi-experimental study monitored changes in target behavior and experiential avoidance (EA) in an individually delivered, 10-session weekly acceptance and commitment therapy intervention. Participants were three university students with elevated EA who endorsed varying mental health concerns. Primary outcome and process variables were daily measures of clinically relevant behavioral excesses (CRB-E) and daily participant-rated EA, respectively. Additionally, we collected weekly measures of EA, along with pre-, mid-, post-treatment, and 3-month follow-up clinical outcome measures. Overall, synchrony across daily, weekly, and pre/post nomothetic measures was largely observed across participants, and findings suggested improvement in clinical outcomes for two of three participants. Daily measurements of CRB-E and EA fluctuated considerably within both baseline and intervention phases. Cross-lagged correlation analyses revealed no evidence of temporal precedence of change in daily measured EA over change in daily measured CRB-E (or vice versa). Implications of these findings and directions for future research are discussed.
AkbariM.SeydaviM.HosseiniZ. S.KrafftJ.LevinM. E. (2022). Experiential avoidance in depression, anxiety, obsessive-compulsive related, and post-traumatic stress disorders: a comprehensive systematic review and meta-analysis. Journal of Contextual Behavioral Science, 24, 65–78. https://doi.org/10.1016/j.jcbs.2022.03.007
2.
ArchJ. J.FishbeinJ. N.FinkelsteinL. B.LuomaJ. B. (2023). Acceptance and commitment therapy processes and mediation: Challenges and how to address them. Behavior Therapy, 54(6), 971–988. https://doi.org/10.1016/j.beth.2022.07.005
3.
ArenaJ. G.ShermanR. A.BrunosG. M.SmithJ. D. (1990). The relationship between situational stress and phantom limb pain: Cross-lagged correlational data from six month pain logs. Journal of Psychosomatic Research, 34(1), 71–77. https://doi.org/10.1016/0022-3999(90)90009-s
4.
ArmstrongA. B. (2011). Acceptance and commitment therapy for adolescent obsessive-compulsive disorder [Unpublished doctoral dissertation]. Utah State University.
5.
AtkinsP. W.CiarrochiJ.GaudianoB. A.BrickerJ. B.DonaldJ.RovnerG.SmoutM.LivheimF.LundgrenT.HayesS. C. (2017). Departing from the essential features of a high quality systematic review of psychotherapy: A response to Öst (2014) and recommendations for improvement. Behaviour Research and Therapy, 97, 259–272.
6.
BeckA. T.SteerR. A. (1993). Beck anxiety inventory manual. Psychological Corporation.
7.
BeckA. T.SteerR. A.BrownG. K. (1996). Manual for the beck depression inventory-II. Psychological Corporation.
8.
BondF. W.HayesS. C.BaerR. A.CarpenterK. M.GuenoleN.OrcuttH. K.WaltzT.ZettleR. D. (2011). Preliminary psychometric properties of the Acceptance and Action Questionnaire–II: A revised measure of psychological inflexibility and experiential avoidance. Behavior Therapy, 42(4), 676–688. https://doi.org/10.1016/j.beth.2011.03.007
9.
BorckardtJ. J.NashM. R.MurphyM. D.MooreM.ShawD.O’NeilP. (2008). Clinical practice as natural laboratory for psychotherapy research: A guide to case-based time-series analysis. American Psychologist, 63(2), 77–95. https://doi.org/10.1037/0003-066X.63.2.77
10.
BoulangerJ. L.HayesS. C.PistorelloJ. (2010). Experiential avoidance as a functional contextual concept. In Emotion regulation and psychopathology: A transdiagnostic approach to etiology and treatment (pp. 107–136). The Guilford Press.
11.
BringmannL. F.FerrerE.HamakerE. L.BorsboomD.TuerlinckxF. (2018). Modeling nonstationary emotion dynamics in dyads using a time-varying vector-autoregressive model. Multivariate Behavioral Research, 53(3), 293–314. https://doi.org/10.1080/00273171.2018.1439722
12.
BrossartD. F.LairdV. C.ArmstrongT. W. (2018). Interpreting Kendall’s Tau and Tau-U for single-case experimental designs. Cogent Psychology, 5, 1–26. https://doi.org/10.1080/23311908.2018.1518687
13.
CaneiroJ. P.SmithA.LintonS. J.MoseleyG. L.O’SullivanP. (2019). How does change unfold? An evaluation of the process of change in four people with chronic low back pain and high pain-related fear managed with cognitive functional therapy: A replicated single-case experimental design study. Behaviour Research and Therapy, 117, 28–39. https://doi.org/10.1016/j.brat.2019.02.007
14.
ChawlaN.OstafinB. (2007). Experiential avoidance as a functional dimensional approach to psychopathology: An empirical review. Journal of Clinical Psychology, 63(9), 871–890. https://doi.org/10.1002/jclp.20400
15.
CiarrochiJ.SahdraB.HofmannS. G.HayesS. C. (2022). Developing an item pool to assess processes of change in psychological interventions: The process-based assessment tool (PBAT). Journal of Contextual Behavioral Science, 23, 200–213. https://doi.org/10.1016/j.jcbs.2022.02.001
16.
DeaconB. J. (2013). The biomedical model of mental disorder: A critical analysis of its validity, utility, and effects on psychotherapy research. Clinical Psychology Review, 33, 846–861. https://doi.org/10.1016/j.cpr.2012.09.007
17.
EifertG. H.ForsythJ. P. (2013). Acceptance and commitment therapy for anxiety disorders: A practitioner’s treatment guide to using mindfulness, acceptance, and values-based behavior change: New Harbinger Publications.
18.
FingerhutJ.MoeyaertM. (2022). Selecting and justifying quantitative analysis techniques in single-case research through a user-friendly open-source tool. Frontiers in Education. https://doi.org/10.3389/feduc.2022.1064807
19.
FirstM. B.WilliamsJ. B.KargR.SpitzerR. L. (2015). Structured clinical interview for DSM-5, research version (SCID-5 for DSM-5, research version; SCID-5-RV). American Psychiatric Association.
20.
FledderusM.Oude VoshaarM. A. H.ten KloosterP. M.BohlmeijerE. T. (2012). Further evaluation of the psychometric properties of the Acceptance and Action Questionnaire–II. Psychological Assessment, 24(4), 925–936. https://doi.org/10.1037/a0028200
21.
GamezW.ChmielewskiM.KotovR.RuggeroC.SuzukiN.WatsonD. (2014). The brief experiential avoidance questionnaire: Development and initial validation. Psychological Assessment, 26, 35–45. https://doi.org/10.1037/a0034473
22.
GlosterA. T.BlockV. J.KlotscheJ.VillanuevaJ.RinnerM. T.BenoyC.WalterM.KareklaM.BaderK. (2021). Psy-Flex: A contextually sensitive measure of psychological flexibility. Journal of Contextual Behavioral Science, 22, 13–23. https://doi.org/10.1016/j.jcbs.2021.09.001
23.
GlosterA. T.WalderN.LevinM. E.TwohigM. P.KareklaM. (2020). The empirical status of acceptance and commitment therapy: A review of meta-analyses. Journal of Contextual Behavioral Science, 18, 181–192. https://doi.org/10.1016/j.jcbs.2020.09.009
24.
GoldbergD. P. (1972). The detection of psychiatric illness by questionnaire. Oxford University Press.
25.
GoldbergD. P.OldehinkelT.OrmelJ. (1998). Why GHQ threshold varies from one place to another. Psychological Medicine, 28(4), 915–921. https://doi.org/10.1017/S0033291798006874
26.
GoldbergD. P.WilliamsP. (1988). A user’s guide to the general health questionnaire. NFER-Nelson.
27.
González-DeleitoC. M.McCrackenL. M.TyrbergM. J. (2024). Ultra-brief acceptance and commitment therapy for inpatients with psychosis—A single case experimental design investigating processes of change. Cognitive Behaviour Therapy, 53(3), 267–285. https://doi.org/10.1080/16506073.2023.2300369
28.
HayesS. C. (2019). A liberated mind: How to pivot toward what matters. Penguin Random House.
29.
HayesS. C.BarlowD. H.Nelson-GrayR. O. (1999). The scientist practitioner: Research and accountability in the age of managed care (2nd ed.). Allyn and Bacon.
30.
HayesS. C.Barnes-HolmesD.WilsonK. G. (2012). Contextual behavioral science: Creating a science more adequate to the challenge of the human condition. Journal of Contextual Behavioral Science, 1, 1–16. https://doi.org/10.1016/j.jcbs.2012.09.004
31.
HayesS. C.CiarrochiJ.HofmannS. G.ChinF.SahdraB. (2022). Evolving an idionomic approach to processes of change: Towards a unified personalized science of human improvement. Behaviour Research and Therapy, 156, 1–23. https://doi.org/10.1016/j.brat.2022.104155
32.
HayesS. C.HofmannS. G. (2021). “Third-wave” cognitive and behavioral therapies and the emergence of a process-based approach to intervention in psychiatry. World Psychiatry, 20(3), 363–375. https://doi.org/10.1002/wps.20884.
33.
HayesS. C.HofmannS. G. (Eds.). (2018). Process-based CBT: The science and core clinical competencies of cognitive behavioral therapy. New Harbinger Publications.
34.
HayesS. C.HofmannS. G. (Eds.). (2020). Beyond the DSM: Toward a process-based alternative for diagnosis and mental health treatment. New Harbinger Publications.
35.
HayesS. C.KingG. A. (2024). Acceptance and commitment therapy: What the history of ACT and the first 1,000 randomized controlled trials reveal. Journal of Contextual Behavioral Science, 33, 100809. https://doi.org/10.1016/j.jcbs.2024.100809
36.
HayesS. C.LevinM. E.Plumb-VilardagaJ.VillatteJ. L.PistorelloJ. (2013). Acceptance and commitment therapy and contextual behavioral science: Examining the progress of a distinctive model of behavioral and cognitive therapy. Behavior Therapy, 44(2), 180–198. https://doi.org/10.1016/j.beth.2009.08.002
37.
HayesS. C.LongD. M.LevinM. E.FolletteW. C. (2013). Treatment development: Can we find a better way?Clinical Psychology Review, 33(7), 870–882. https://doi.org/10.1016/j.cpr.2012.09.009
38.
HayesS. C.LuomaJ. B.BondF. W.MasudaA.LillisJ. (2006). Acceptance and commitment therapy: Model, processes and outcomes. Behaviour Research and Therapy, 44(1), 1–25. https://doi.org/10.1016/j.brat.2005.06.006
39.
HayesS. C.MerwinR. M.McHughL.SandozE. K.A-TjakJ. G. L.RuizF. J.Barnes-HolmesD.BrickerJ. B.CiarrochiJ.DixonM. R.FungK. P. L.McCrackenL. M. (2021). Report of the ACBS Task Force on the strategies and tactics of contextual behavioral science research. Journal of Contextual Behavioral Science, 20, 172–183. https://doi.org/10.1016/j.jcbs.2021.03.007
40.
HayesS. C.StrosahlK. D.WilsonK. G. (2012). Acceptance and commitment therapy: The process and practice of mindful change (2nd ed.). Guilford Press.
41.
HayesS. C.WilsonK. G.GiffordE. V.FolletteV. M.StrosahlK. (1996). Experiential avoidance and behavioral disorders: A functional dimensional approach to diagnosis and treatment. Journal of Consulting and Clinical Psychology, 64(6), 1152–1168. https://doi.org/10.1037/0022-006X.64.6.1152
42.
HaynesS. N.O’BrienW. H. (2000). Principles and practice of behavioral assessment. Springer.
43.
HaynesS. N.SpencerS. D.LabaT. M. (2022). Principles and practices of behavioral assessment. In BagbyM.AsmundsonG. (Eds.) Comprehensive clinical psychology (2nd ed.). Elsevier. https://dx.doi.org/10.1016/B978-0-12-818697-8.00072-8
44.
HerbertM. S.AfariN.LiuL.HeppnerP.RutledgeT.WilliamsK.EarlyS.VanBuskirkK.NguyenC.BondiM.AtkinsonJ. H.WetherellJ. L. (2017). Telehealth versus in-person acceptance and commitment therapy for chronic pain: A randomized noninferiority trial. The Journal of Pain, 18(2), 200–211. https://doi.org/10.1016/j.jpain.2016.10.014
45.
HerzbergK. N.SheppardS. C.ForsythJ. P.CredeM.EarlywineM.EifertG. H. (2012). The believability of anxious feelings and thoughts questionnaire (BAFT): A psychometric evaluation of cognitive fusion in a nonclinical and highly anxious community sample. Psychological Assessment, 24(4), 877–891. https://doi.org/10.1037/a0027782
46.
HesserH.WestinV.HayesS. C.AnderssonG. (2009). Clinets’ in-session acceptance and cognitive defusion behaviors in acceptance-based treatment of tinnitus distress. Behaviour Research and Therapy, 47, 523–528. https://doi.org/10.1016/j.brat.2009.02.002
47.
HewittP. L.NortonG. R. (1993). The Beck Anxiety Inventory: A psychometric analysis. Psychological Assessment, 5(4), 408–412. https://doi.org/10.1037/1040-3590.5.4.408
48.
HillM. L.SchaeferL. W.SpencerS. D.MasudaA. (2020). Compassion-focused acceptance and commitment therapy for women with restrictive eating and problematic body-checking: a multiple baseline design across participants study. Journal of Contextual Behavioral Science, 16, 144–152. https://doi.org/10.1016/j.jcbs.2020.04.006
49.
HitchcockJ. H.KratochwillT. R.ChezanL. C. (2015). What works clearinghouse standards and generalization of single-case design evidence. Journal of Behavioral Education, 24, 459–469. https://doi.org/10.1007/s10864-015-9224-1
50.
HofmannS. G.HayesS. C. (2019). The future of intervention science: Process-based therapy. Clinical Psychological Science, 7(1), 37–50. https://doi.org/10.1177/2167702618772296
51.
JacobsonN. S.TruaxP. (1991). Clinical significance: A statistical approach to defining meaningful change in psychotherapy research. Journal of Consulting and Clinical Psychology, 59, 12–19. https://doi.org/10.1037//0022-006x.59.1.12
52.
KazdinA. E. (2019). Single-case research designs: Methods for clinical and applied settings (2nd ed.). Oxford University Press.
53.
KingstonJ.ClarkeS.RemingtonB. (2010). Experiential avoidance and problem behavior: A mediational analysis. Behavior Modification, 34(2), 145–163. https://doi.org/10.1177/0145445510362575
54.
KlimczakK. S.SchwartzS. E.DonahueM. L.CapelL. K.SnowJ. L.LevinM. E. (2023). Disentangling trait and state psychological inflexibility: A longitudinal multilevel approach. Journal of Contextual Behavioral Science, 29, 13–22. https://doi.org/10.1016/j.jcbs.2023.05.006
KwasnickaD.NaughtonF. (2020). N-of-1 methods: A practical guide to exploring trajectories of behaviour change and designing precision behaviour change interventions. Psychology of Sport & Exercise, 47, 101570. https://doi.org/10.1016/j.psychsport.2019.101570
57.
LaneJ. D.GastD. L. (2014). Visual analysis in single case experimental design studies: Brief review and guidelines. Neuropsychological Rehabilitation, 24(3–4), 445–463. https://doi.org/10.1080/09602011.2013.815636
58.
LanovazM. J.TurgeonS. (2020). How many tiers do we need? Type I errors and power in multiple baseline designs. Perspectives on Behavior Science, 43(3), 605–616. https://doi.org/10.1007/s40614-020-00263-x
59.
LoerincA. G.MeuretA. E.TwohigM. P.RosenfieldD.BluettE. J.CraskeM. G. (2015). Response rates for CBT for anxiety disorders: Need for standardized criteria. Clinical Psychology Review, 42, 72–82. https://doi.org/10.1016/j.cpr.2015.08.004
60.
LuckS. A. M.Golijani-MoghaddamN.DawsonD. L. (2024). A systematic quality review of single-case experimental designs using acceptance and commitment therapy in adult clinical populations. Behavior Therapy, 55(4), 856–871. https://doi.org/10.1016/j.beth.2024.01.008
61.
LundgrenT.LuomaJ. B.DahlJ.StrosahlK.MelinL. (2012). The Bull’s-Eye Values Survey: A psychometric evaluation. Cognitive and Behavioral Practice, 19(4), 518–526. https://doi.org/10.1016/j.cbpra.2012.01.004
62.
LutzW.de JongK.RubelJ. A.DelgadilloJ. (2021). Measuring, predicting, and tracking change in psychotherapy. In BarkhamM.LutzW.CastonguayL. G. (Eds.), Bergin and Garfield’s handbook of psychotherapy and behavior change: 50th anniversary edition (7th ed., pp. 89–133). Wiley.
63.
MacriJ. A.RoggeR. D. (2024). Examining domains of psychological flexibility and inflexibility as treatment mechanisms in acceptance and commitment therapy: A comprehensive systematic and meta-analytic review. Clinical Psychology Review, 110, 102432. https://doi.org/10.1016/j.cpr.2024.102432
64.
McKnightS. D.McKeanJ. W.HuitemaB. E. (2000). A double bootstrap method to analyze linear models with autoregressive error terms. Psychological Methods, 5(1), 87–101. https://doi.org/10.1037/1082-989X.5.1.87
65.
MenninD. S.EllardK. K.FrescoD. M.GrossJ. J. (2013). United we stand: Emphasizing commonalities across cognitive-behavioral therapies. Behavior Therapy, 44(2), 234–248. https://doi.org/10.1016/j.beth.2013.02.004
66.
MichielsB.OnghenaP. (2019). Randomized single-case AB phase designs: Prospects and pitfalls. Behavior Research Methods, 51(6), 2454–2476. https://doi.org/10.3758/s13428-018-1084-x
67.
MiltenbergerR. G. (2016). Behavior modification: Principles and procedures. Cengage Learning.
68.
MoskowD. M.OngC. W.HayesS. C.HofmannS. G. (2023). Process-based therapy: A personalized approach to treatment. Journal of Experimental Psychopathology, 14(1), 1–8. https://doi.org/10.1177/20438087231152848
69.
MurisP.MerckelbachH.HorselenbergR. (1996). Individual differences in thought suppression. The white bear suppression inventory: Factor structure, reliability, validity, and correlates. Behavior Research & Therapy, 34, 501–513. https://doi.org/10.1016/0005-7967(96)00005-8
OngC. W.CiarrochiJ.HofmannS. G.KareklaM.HayesS. C. (2024). Through the extended evolutionary meta-model, and what ACT found there: ACT as a process-based therapy. Journal of Contextual Behavioral Science, 32, 100734. https://doi.org/10.1016/j.jcbs.2024.100734
72.
OngC. W.HayesS. C.HofmannS. G. (2022). A process-based approach to cognitive behavioral therapy: A theory-based case illustration. Frontiers in Psychology, 13:1002849. https://doi.org/10.3389/fpsyg.2022.1002849
73.
OngC. W.LevinM. E.TwohigM. P. (2020). Beyond acceptance and commitment therapy: Process-based therapy. The Psychological Record, 70, 637–648. https://doi.org/10.1007/s40732-020-00397-z
74.
PalA.PrakashP. K. S. (2017). Practical time series analysis: Master time series data processing, visualization, and modeling using python. Packt Publishing.
75.
ParkerR. I.VannestK. J.DavisJ. L.SauberS. B. (2011). Combining non-overlap and trend for single-case research: Tau-U. Behavior Therapy, 42(2), 284–299. https://doi.org/10.1016/j.beth.2010.08.006
76.
PersonsJ. B.ThomasC.HsiaoM.CourryR. (2023). How to build a research database from data you collect to guide your clinical work. Cognitive and Behavioral Practice, 30(1), 35–44. https://doi.org/10.1016/j.cbpra.2021.10.002
77.
PlumbJ. C.VilardagaR. (2010). Assessing treatment integrity in acceptance and commitment therapy: Strategies and suggestions. International Journal of Behavior and Cognitive Therapies, 6(3), 263–295. https://doi.org/10.1037/h0100912
78.
SahdraB. K.CiarrochiJ.KlimczakK.KrafftJ.HayesS. C.LevinM. (2024). Testing the applicability of idionomic statistics in longitudinal studies: The example of ‘doing what matters.’ Journal of Contextual Behavioral Science, 32, 100728. https://doi.org/10.1016/j.jcbs.2024.100728
79.
SanfordB. T.CiarrochiJ.HofmannS. G.ChinF.GatesK. M.HayesS. C. (2022). Toward empirical process-based case conceptualization: An idionomic network examination of the process-based assessment tool. Journal of Contextual Behavioral Science, 25, 10–25. https://doi.org/10.1016/j.jcbs.2022.05.006
80.
SkevingtonS. M.LotfyM.O’ConnellK. A., & The WHOQOL Group. (2004). The World Health Organization’s WHOQOL-BREF quality of life assessment: Psychometric properties and results of the international field trial. A report from the WHOQOL group. Quality of Life Research, 13, 299–310. https://doi.org/10.1023/B:QURE.0000018486.91360.00
81.
SpencerS. D. (2023). Acceptance and commitment therapy as a transdiagnostic, process-based approach to treatment for mental health concerns: A mechanism of change analysis using a multiple baseline design across participants [Unpublished doctoral dissertation]. University of Hawaii at Manoa.
82.
SpencerS. D.JoD.HamagamiF.AntonioM. C. K.QinaʻauJ.MasudaA.HishinumaE. S. (2022). A psychometric validation of contextual cognitive behavioral therapy-informed measures with radically and ethnically diverse adults. Journal of Contextual Behavioral Science, 25, 61–72. https://doi.org/10.1016/j.jcbs.2022.06.004
83.
SpencerS. D.MasudaA. (2020). Acceptance and commitment therapy as a transdiagnostic approach to treatment of behavioral health concerns: A concurrent multiple baseline design across participants. Clinical Case Studies, 19(3), 163–179. https://doi.org/10.1177/1534650119897412
84.
SpencerS. D.MeyerM. S.MasudaA. (2023). A case-series study examining acceptance and commitment therapy for experiential avoidance-related mixed anxiety and depression in a telehealth platform. Clinical Case Studies, 22(1), 1–19. https://doi.org/10.1177/15346501221115113
85.
SpringerK. S.LevyH. C.TolinD. F. (2018). Remission in CBT for adult anxiety disorders: A meta-analysis. Clinical Psychology Review, 61, 1–8. https://doi.org/10.1016/j.cpr.2018.03.002
86.
StocktonD.KellettS.BerriosR.SiroisF.WilkinsonN.MilesG. (2019). Identifying the underlying mechanisms of change during acceptance and commitment therapy (ACT): A systematic review of contemporary mediation studies. Behavioral and Cognitive Psychotherapy, 47(3), 332–362. https://doi.org/10.1017/S1352465818000553
87.
TarlowK. R. (2017). An improved rank correlation effect size statistic for single-case designs: Baseline corrected Tau. Behavior Modification, 41(4), 427–467. https://doi.org/10.1177/0145445516676750
88.
TrompetterH. R.JohnstonD. W.JohnstonM.Vollenbroek-HuttenM. M.SchreursK. M. G. (2019). Are processes in Acceptance & Commitment Therapy (ACT) related to chronic pain out-comes within individuals over time? An exploratory study using n-of-1 designs. Journal for Person-Oriented Research, 5(2), 123–136. https://doi.org/10.17505/jpor.2019.11
89.
TrompetterH. R.ten KloosterP. M.SchreursK. M. G.FledderusM.WesterhofG.BohlmeijerE. T. (2013). Measuring values and committed action with the engaged living scale (ELS): Psychometric evaluation in a nonclinical sample and a chronic pain sample. Psychological Assessment, 25, 1235–1246. https://doi.org/10.1037/a0033813
90.
TwohigM. P.HayesS. C.MasudaA. (2006a). Increasing willingness to experience obsessions: Acceptance and commitment therapy as a treatment for obsessive-compulsive disorder. Behavior Therapy, 37(1), 3–13. https://doi.org/10.1016/j.beth.2005.02.001
91.
TwohigM. P.HayesS. C.MasudaA. (2006b). A preliminary investigation of Acceptance and Commitment Therapy as a treatment for chronic skin picking. Behaviour Research and Therapy, 44, 1513–1522. https://doi.org/10.1016/j.brat.2005.10.002
92.
TwohigM. P.HayesS. C.PlumbJ. C.PruittL. D.CollinsA. B.Hazlett-StevensH.WoidneckM. R. (2010). A randomized clinical trial of acceptance and commitment therapy versus progressive relaxation training for obsessive-compulsive disorder. Journal of Consulting and Clinical Psychology, 78(5), 705. https://doi.org/10.1037/a0020508
93.
TwohigM. P.LevinM. E. (2017). Acceptance and commitment therapy as a treatment for anxiety and depression: A review. Psychiatric Clinics of North America, 40(4), 751–770. https://doi.org/10.1016/j.psc.2017.08.009
94.
TwohigM. P.ShoenbergerD.HayesS. C. (2007). A preliminary investigation of acceptance and commitment therapy as a treatment for marijuana dependence in adults. Journal of Applied Behavior Analysis, 40(4), 619–632.
95.
TyndallI.WaldeckD.PancaniL.WhelanR.RocheB.DawsonD. L. (2019). The Acceptance and Action Questionnaire-II (AAQ-II) as a measure of experiential avoidance: Concerns over discriminant validity. Journal of Contextual Behavioral Science, 12, 278–284. https://doi.org/10.1016/j.jcbs.2018.09.005
96.
VannestK. J.ParkerR. I.GonenO.AdiguzelT. (2016). Single case research: Web-based calculators for SCR analysis (Version 2.0) [web-based application]. Texas A&M University. Retrieved March 27, 2025, from https://singlecaseresearch.org/calculators/tau-u/
97.
VilardagaR.VilardagaJ. P. (2019). Marching our values forward: Progressing contextual behavioral science in line with its core epistemic assumptions. Journal of Contextual Behavioral Science, 14, 108–110. https://doi.org/10.1016/j.jcbs.2019.10.002
98.
VillatteJ. L.VilardagaR.VillatteM.Plumb-VilardagaJ. C.AtkinsD. C.HayesS. C. (2016). Acceptance and commitment therapy modules: Differential impact on treatment processes and outcomes. Behaviour Research and Therapy, 77, 52–61. https://doi.org/10.1016/j.brat.2015.12.001
99.
WakefieldJ. C. (2016). Diagnostic issues and controversies in DSM-5: Return of the false positives problem. Annual Review of Clinical Psychology, 12, 105–132. https://doi.org/10.1146/annurev-clinpsy-032814-112800
100.
WaltzT. J.DrosselC. (2023). Primer on basic behavioral principles. In TwohigM. P.LevinM. E.PetersenJ. M. (Eds.), The Oxford handbook of acceptance and commitment therapy (pp. 42–76). Oxford University Press.
WernekeU.GoldbergD. P.YalcinI.UstunB. T. (2000). The stability of the factor structure of the General Health Questionnaire. Psychological Medicine, 30, 823–829. https://doi.org/10.1017/s0033291799002287
WicksellR. K.OlssonG. L.HayesS. C. (2012). Psychological flexibility as a mediator of improvement in acceptance and commitment therapy for patients with chronic pain following whiplash. European Journal of Pain, 14(10), 1059.e1–1059.e11. https://doi.org/10.1016/j.ejpain.2010.05.001
105.
WolgastM. (2014). What does the Acceptance and Action Questionnaire (AAQ-II) really measure?Behavior Therapy, 45(6), 831–839. https://doi.org/10.1016/j.beth.2014.07.002
