Long-term stability of early sudden gains in an acceptance and values-based intervention

This is a sel -a chi ed e sion o an o iginal a icle. This e sion may di e om he o iginal in pagina ion and ypog aphic de ails. Au ho (s): Ti le: Yea : Ve sion: Copy igh : Righ s: Righ s u l: Please ci e he o iginal e sion: CC BY-NC-ND 4.0 h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/ Long- e m s abili y o ea ly sudden gains in an accep ance and alues-based in e en ion © 2019 Associa ion o Con ex ual Beha io al Science. Accep ed e sion (Final d a ) Keinonen, Ka a iina; Kyllönen, Heidi; As ikainen, Piia; Lappalainen, Raimo Keinonen, K., Kyllönen, H., As ikainen, P., & Lappalainen, R. (2019). Long- e m s abili y o ea ly sudden gains in an accep ance and alues-based in e en ion. Jou nal o Con ex ual Beha io al Science, 13(52-59). h ps://doi.o g/10.1016/j.jcbs.2019.06.006 2019 Accep ed Manusc ip Long- e m s abili y o ea ly sudden gains in an accep ance and alues-based in e en ion Ka a iina Keinonen, Heidi Kyllönen, Piia As ikainen, Raimo Lappalainen PII: S2212-1447(18)30334-X DOI: h ps://doi.o g/10.1016/j.jcbs.2019.06.006 Re e ence: JCBS 311 To appea in: Jou nal o Con ex ual Beha io al Science Recei ed Da e: 18 Decembe 2018 Re ised Da e: 3 June 2019 Accep ed Da e: 25 June 2019 Please ci e his a icle as: Keinonen K., Kyllönen H., As ikainen P. & Lappalainen R., Long- e m s abili y o ea ly sudden gains in an accep ance and alues-based in e en ion, Jou nal o Con ex ual Beha io al Science (2019), doi: h ps://doi.o g/10.1016/j.jcbs.2019.06.006. This is a PDF ile o an unedi ed manusc ip ha has been accep ed o publica ion. As a se ice o ou cus ome s we a e p o iding his ea ly e sion o he manusc ip . The manusc ip will unde go copyedi ing, ypese ing, and e iew o he esul ing p oo be o e i is published in i s inal o m. Please no e ha du ing he p oduc ion p ocess e o s may be disco e ed which could a ec he con en , and all legal disclaime s ha apply o he jou nal pe ain. MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT Long- e m s abili y o ea ly sudden gains in an accep ance and alues-based in e en ion Ka a iina Keinonen, Heidi Kyllönen, Piia As ikainen and Raimo Lappalainen Depa men o Psychology, Uni e si y o Jy äskylä P.O. Box 35, FI-40014 Uni e si y o Jy äskylä, Finland Au ho con ac in o ma ion: Ka a iina Keinonen, M.S., co esponding au ho , e-mail: ka a iina.keinonen@jyu. i Heidi Kyllönen, M.S., e-mail: [email p o ec ed] Piia As ikainen, Ph.D., e-mail: [email p o ec ed] Raimo Lappalainen, Ph.D., e-mail: aimo.lappalainen@jyu. i MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT Long- e m S abili y o Ea ly Sudden Gains in an Accep ance and Values-based In e en ion Re-submi ed: 03.06.2019 MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT Abs ac Though p e ious esea ch has ex ensi ely epo ed ha sudden gains a e associa ed wi h supe io ea men esul s, esea ch on he long- e m e ec s and s abili y o sudden gains is no as consis en . The cu en s udy explo ed he long- e m s abili y o ea ly sudden gains (ESGs) obse ed in a b ie accep ance and alues-based in e en ion o dep ession p o ided by no ice he apis s. The pa icipan s we e 56 olun ee s diagnosed wi h majo dep essi e diso de . Among he pa icipan s, 23% expe ienced ESGs, i.e. hey eached he s a us o imp o ed o eco e ed in he Reliable Change Index (RCI; Jacobson & T uax, 1991) classi ica ion a e only wo sessions. The cu en s udy examined he le el o dep essi e symp oms (BDI-II), psychological lexibili y (AAQ-II), belie abili y o dep essi e hough s (ATQ-B), and hope ulness (ASHS) 6 and 12 mon hs a e he in e en ion. O he o iginal pa icipan s, 77% (n = 43) ook pa in he 12-mon h ollow-up. The esul s showed ha posi i e changes achie ed du ing he wo i s sessions in he ESG g oup we e main ained up o 12 mon hs a e he in e en ion. The ESG g oup emained imp o ed o eco e ed in he RCI classi ica ion h ough he 12-mon h ollow-up pe iod. Howe e , a he 12-mon h ollow- up, he e we e only small di e ences be ween he ESG and he non-ESG g oups. The esul s sugges ha pa icipan s achie ing ESGs show s able imp o emen s las ing up o 12 mon hs a e he ea men . Keywo ds: Ea ly sudden gains, long- e m ou come, dep ession, no ice he apis s, b ie in e en ion. MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT In oduc ion In he ea men o dep ession and a ious anxie y diso de s, sudden gains—i.e. la ge, s able, and sudden changes in symp om se e i y—ha e been associa ed wi h supe io ea men ou comes a pos ea men (e.g., Hedman e al., 2014; Kelle , Feeny, & Zoellne , 2014; No on, Klenck, & Ba e a, 2010). A me a-analysis o 16 s udies on sudden gains showed he e ec size ha sudden gains ha e on ea men ou comes is pa icula ly la ge (Hedges’ g = 0.75) when cogni i e beha io al ea men s a e employed (Ade ka, Nicke son, Bøe, & Ho mann, 2012). As he ypical magni ude o sudden gains is ela i ely la ge—a ound 10–13 poin s on he Beck Dep ession In en o y (BDI; Beck & S ee , 1987; e.g., Tang, DeRubeis, Hollon, Ams e dam, & Shel on, 2007)—sudden gains appea o ha e high clinical ele ance du ing he ea men . O e all, sudden gains occu ing a a ious s ages o ea men a e an in e es ing sub ype o imp o emen no only due o he supe io ea men esul s ha hey a e associa ed wi h bu also due o he high equency a which hey occu . S udies ha e ypically epo ed ha app oxima ely 30–40% o pa icipan s expe ience a leas one sudden gain du ing he ea men (e.g., Hunnicu -Fe guson, Hoxha, & Gollan, 2012; Tang e al., 2007). These esul s sugges ha unde s anding sudden gains may help clinicians o iden i y and ake ad an age o his d ama ic and equen phenomenon. One o he ea u es o sudden gains ha s ill needs o be cla i ied is how a eaching he e ec s o sudden gains a e on ea men esul s. Whe eas se e al s udies ha e epo ed he e ec o sudden gains immedia ely a e ea men , epo s o long- e m ea men esul s a e a e . Some encou aging indings can be ound, howe e . In he ea men o dep ession, sudden gains ha e been associa ed wi h lowe a es o elapse and symp om ecu ence du ing a wo-yea ollow-up phase (Tang e al., 2007). In he ea men o anxie y diso de s, i has been epo ed ha sudden gains a e associa ed wi h supe io ea men esul s up o 12-mon h ollow-up (Bohn, Ade ka, MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT Sch eibe , S angie , & Ho mann, 2013; Hedman e al., 2014). Simila ly, Ade ka, Appelbaum- Namda , Sha an, and Gilboa-Schech man (2011) ound ha child en who had sudden gains while being ea ed o pos auma ic s ess diso de had supe io ea men ou comes a pos ea men , and hey main ained he ad an age a 12-mon h ollow-up. In line wi h hese esul s, a me a-analysis showed ha sudden gains ha e a mode a e e ec a ollow-up compa ed o hose no epo ing sudden gains du ing he ea men (n = 8 s udies, Hedges’ g = 0.56, pooled ollow-up du a ions, mean [M] = 4.44 mon hs; Ade ka e al., 2012). Also, a s udy by Lemmens, DeRubeis, A n z, Pee e s, and Huibe s (2016) sugges ed ha sudden gains ha e p ognos ic alue up o i e mon hs a e ea men bu no a e 12 mon hs. Mo e s udies a e needed o d aw conclusions on how s able he changes associa ed wi h sudden gains a e and how a eaching he ad an age is when compa ed o hose no expe iencing sudden gains. Sudden gains can occu a any poin du ing he ea men , bu some s udies ha e epo ed ha hei equency is highe du ing he i s ew sessions (e.g., Hunnicu -Fe guson e al., 2012; Mas e son e al., 2014). Fo example, Dou , Cho pi a, Lee and Weisz (2013) obse ed ha sudden gains we e mo e likely o occu be ween he second and hi d sessions han a any o he ime, and mos o he obse ed sudden gains occu ed be o e session six. Simila ly, Hunnicu - Fe guson e al. (2012) ound ha he equency o sudden gains was highes o he i s session, and, again, mos sudden gains occu ed be o e session six. The a ailable s udies ha ocus on ea ly sudden gains (ESG) ha e epo ed somewha mixed esul s on he e ec on he ea men ou come. ESG is a simila concep o ha o apid esponse, ha e e s o clinically signi ican changes a e he i s ou weeks o he ea men . Howe e , ESG e e s o la ge and clinically signi ican changes du ing hese i s ou weeks o ea men . Whe eas some ha e ound ha ESGs p edic o e all ea men ou come (e.g., Hunnicu - Fe guson e al., 2012; Kelly, Robe s, & Ciesla, 2005), he e a e also s udies ha ha e ound ha ESGs do no p edic be e ou comes (Dou e al., 2013). In addi ion, Cle kin, Teachman, and MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT Smi h-Janik (2008) epo ed ha sudden gains occu ing a e session one do no p edic g ea e imp o emen s, bu sudden gains occu ing a e session wo do p edic g ea e imp o emen s. In acco dance wi h his, we ha e p e iously epo ed ha sudden gains occu ing be o e he hi d session p edic a be e o e all ea men esponse in he ea men o dep ession as measu ed a pos ea men (omi ed om blinded e iew, 2018). Finally, i has been sugges ed ha ESGs (i.e. sudden gains occu ing du ing he i s hi d o he ea men ) may be mo e signi ican o ea men esul s han sudden gains occu ing la e in he ea men (Kelly e al., 2005). Based on he a ailable s udies, u he explo a ion o he clinical and heo e ical impo ance o ESGs is needed. In addi ion o he need o mo e s udies wi h longe ollow-ups, we also need mo e s udies ha in es iga e sudden gains in ea men s p o ided by inexpe ienced he apis s. I sudden gains consis en ly occu in ea men s p o ided by no ice he apis s, his may sugges sudden gains a e no ela ed o ex ensi e aining o high compe ence. Indeed, G een ield, Gun he , and Haaga (2011) ha e epo ed ha no ice he apis s wo king in a psycho he apy aining clinic p oduced sudden gains a a compa able equency (23% o pa icipan s expe ienced sudden gains) o ha epo ed o expe ienced he apis s. To ou knowledge, he e a e no s udies epo ing he long- e m s abili y o sudden gains in he ea men s adminis a ed by no ice he apis s. The cu en s udy aims o ex end ou unde s anding o sudden gains by explo ing he e ec s o ESGs on long- e m ea men esul s in an accep ance and alues-based ea men (ACT) p o ided by no ice he apis s. We ha e p e iously epo ed ha ESG was associa ed wi h supe io ea men esul s a pos ea men in a six-session in e en ion deli e ed by s uden he apis s wi hou any p io clinical expe ience (omi ed om masked e iew, 2018). All pa icipan s we e diagnosed as ha ing a majo dep essi e diso de , and ESG was de ined as being classi ied as imp o ed o eco e ed acco ding o he RCI classi ica ion (Jacobson & T uax, 1991) using Beck Dep ession In en o y-II sco es a e only wo sessions (BDI-II; Beck, S ee , & B own, 2004). We ound ha 23% o pa icipan s eached he s a us o ea ly sudden gaine s using he RCI me hod o MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT iden i y ESG (omi ed om blinded e iew, 2018). Supe io ea men ou comes we e de ec ed on bo h he le el o dep essi e symp oma ology and on he le el o psychological lexibili y, which was used as a seconda y measu e o he apeu ic change (omi ed om blinded e iew, 2018). In he cu en s udy, we in es iga ed whe he signi ican changes in dep ession symp oms occu ing a ea ly s ages o ea men (i.e. du ing he i s wo weeks) p edic he long- e m ea men ou come when pa icipan s diagnosed wi h a majo dep essi e diso de we e o e ed a six-session ACT in e en ion deli e ed by inexpe ienced he apis s. We wan ed o explo e: (1) A e ESGs ha a e obse ed in dep ession symp oms wi hin he wo i s sessions main ained a e he in e en ion? Do hose who show ESGs in dep ession show supe io long- e m ea men ou comes (a 6 and 12 mon hs) on he le els o dep essi e symp oma ology, psychological lexibili y, hope ulness, and belie abili y o dep essi e hough s? (2) How s ong is he associa ion be ween ESGs and long- e m ea men esul s (a 6 and 12 mon hs)? (3) A e ESGs associa ed wi h he RCI classi ica ion s a us ( eco e ed, imp o ed, unchanged, o declined), he use o medica ion o dep ession, o psychological ea men o dep ession a he 6- and/o 12-mon h ollow-up phases? Me hod Pa icipan s The cu en s udy is pa o a la ge s udy examining he e icacy o a six-session ACT in e en ion o majo dep essi e diso de deli e ed by no ice he apis s (omi ed om blinded e iew, 2018). The pa icipan s we e olun ee s wi h a diagnosis o majo dep essi e diso de ha was based on he c i e ia in he In e na ional Classi ica ion o Diseases (Wo ld Heal h O ganiza ion, 1992) and was ob ained in an in e iew wi h a medical doc o as a pa o he ec ui men o he s udy. Exclusion c i e ia o he s udy we e: (1) psychia ic diagnosis o he han dep ession, (2) neu ological diagnosis, (3) misuse o alcohol o d ugs, and (4) on-going psychological ea men . MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT was 13 sco es, and in he N-ESG g oup, i was 3 sco es (Omi ed om masked e iew, 2018). The e we e no signi ican p e ea men di e ences be ween he g oups on any o he measu es used. Figu e 2. Le el o dep ession (BDI-II), psychological lexibili y (AAQ-2), belie abili y o dep essi e hough s (ATQ-B), and hope ulness (ASHS) a p e ea men , a e wo sessions, 6- mon h ollow-up, and 12-mon h ollow-up wi h be ween-g oup e ec sizes. Fi s , gi en he la ge di e ence in he change o dep ession symp oms du ing he wo i s sessions be ween he ESG and N-ESG g oups, we we e in e es ed in how hese g oups changed o e ime a e he b ie in e en ion ended. A se ies o ANOVA analyses wi h he ESG g oup as he be ween-g oups a iable and le el o dep ession, psychological lexibili y, hope ulness, and belie abili y o dep essi e hough s as he dependen a iables (measu ed a p e ea men , 6-mon h ollow-up and 12-mon h ollow-up). The ANOVA analyses showed ha he e we e no p e ea men di e ences be ween he g oups, bu he ESG g oup epo ed signi ican ly lowe dep ession (F 1,40 = 10.79, p = .002), highe psychological lexibili y (F 1,37 = 4.70, p = .037) and highe hope ulness (F 1,44 = 5.72, p = .021) a he six-mon h ollow-up (see Table 3). In acco dance wi h his, he be ween-g oup e ec size indica ed ha he e was a la ge di e ence (d ≥ 0.80) in dep ession symp oms, a la ge di e ence (d ≥ 0.80) in hope ulness (ASHS), a mode a e (d ≥ 0.50) di e ence in psychological lexibili y (AAQ-2), and a small di e ence in belie abili y o dep essi e hough s (ATQ-B) in a o o he ESG g oup a 6-mon h ollow-up. A he 12-mon h ollow-up, he e we e no signi ican di e ences be ween he g oups on any a iable. Howe e , when in es iga ing he e ec sizes a 12-mon h ollow-up, he e we e small be ween-g oup di e ences (d ≥ 0.20 - < 0.50) in dep ession symp oms, psychological lexibili y, and hope ulness (ASHS) in a o o he ESG g oup. The di e ence in belie abili y o dep essi e hough s (ATQ-B) was e y small. MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT O e all, as we can see om Figu e 2, he changes in he ESG g oup we e main ained du ing he 12-mon h ollow-up pe iod. The 95% con idence in e als o change sco es om p e ea men o 12-mon h ollow-up we e as ollows: o BDI-II, ESG (14.21, 22.40) and N-ESG (11.20, 17.11); o AAQ-2, ESG (-7.15, -24.85) and N-ESG (-6.34, -15.17); o ASHS, ESG (-4.85, -25.95) and N-ESG (-8.01, -14.84); and o ATQ-B, ESG (14.48, 43.32) and N-ESG (11.72, 30.34). Second, we we e in e es ed in whe he he change in dep ession symp oms du ing he i s wo sessions was associa ed wi h he obse ed changes om he p e- ea emen o he 12- mon h ollow-up. When analyzing he o al sample, he e we e signi ican co ela ions be ween he magni ude o ESG (i.e. ea ly changes in dep ession) and he long- e m ea men ou come o dep ession (12 mon hs = 0.36, p ≤ 0.05, n = 43), psychological lexibili y (12 mon hs = -0.33, p ≤ 0.05, n = 43), and hope ulness (12 mon hs = -0.29, p ≤ 0.05, n = 43). Change in belie abili y o dep essi e hough s up o 12-mon h ollow-up was no signi ican ly associa ed wi h ea ly changes in dep essi e symp oma ology. Thi d, we we e in e es ed in he clinical signi icance o ESGs. The RCI classi ica ion o he ESG and N-ESG g oups 6 and 12 mon hs a e he ea men suppo he esul s abo e. The numbe o pa icipan s classi ied as eco e ed in he ESG g oup was e y high a bo h 6- and 12- mon hs ollow-up (Table 4) suppo ing he s abili y o ea ly changes. Howe e , no signi ican di e ences be ween he g oups we e ob ained. Also, he e was no di e ence be ween he g oups in he use o medica ion o dep ession du ing he ollow-up. Ve y ew o he pa icipan s in he ESG g oup ecei ed ea men du ing he ollow-up (n = 1/10 a 12-mon h ollow-up). Table 4. RCI classi ica ion equencies, use o medica ion o dep ession, and psychological ea men a e he in e en ion and Pea son’s chi-squa ed es o he ea ly sudden gain (ESG) g oup and he non-ea ly sudden gain (N-ESG) g oup 6 and 12 mon hs a e ea men . MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT Discussion The aim o he cu en s udy was o explo e he s abili y o ESGs in a six-session ACT in e en ion deli e ed by no ice he apis s. We ha e p e iously epo ed ha ESG was associa ed wi h a supe io ea men ou come a pos ea men (omi ed om blinded e iew, 2018). In he cu en s udy, we examined he long- e m e ec o ESG obse ed wi hin wo sessions on changes in symp om and he apeu ic p ocess measu es om p e ea men o 6- and 12-mon h ollow-up phases. The esul s sugges ed ha ESG in dep ession symp oms esul ed in a s able change ha pe sis ed h ough he ollow-up phases up o 12 mon hs. Thus, oughly 20% o clien s diagnosed as ha ing a majo dep essi e diso de showed clinically signi ican changes in dep ession symp oms wi hin wo sessions, and hese changes we e main ained 12 mon hs a e he in e en ion. The esul s we e suppo ed by he RCI classi ica ion a 6 and 12 mon hs a e ea men : a e y high numbe o he ESG g oup membe s who pa icipa ed in he ollow-up phase we e s ill imp o ed ( eco e ed o imp o ed in he RCI classi ica ion) sugges ing ha ESG is a e y s able imp o emen . Fu he , la ge changes in dep ession symp oms du ing he wo i s sessions p edic ed la ge changes in dep ession symp oms, psychological lexibili y, and hope ulness a he 12-mon h ollow-up. Howe e , hose pa icipan s no showing ESG achie ed an equal posi i e change a 12-mon h ollow-up a e he in e en ion. The esul s a e in line wi h hose epo ed by Lemmens e al. (2016) in ha sudden changes du ing he ea men do p oduce be e ollow-up esul s up o a ce ain poin (i.e. i e mon hs), bu he g oup di e ences e en ually ade. Simila ly, in he cu en s udy, he ESG g oup showed a be e ou come a he 6-mon h ollow-up, pa icula ly in dep ession symp om. Howe e , a he 12-mon h ollow-up, he di e ences be ween he ESG and N-ESG g oups we e small. Tang e al. (2007) also epo ed ha sudden gains we e associa ed wi h lowe elapse and symp om ecu ence a es. Al hough he di e ences be ween he ESG and N-ESG g oups we e non- MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT signi ican in he RCI classi ica ion a ollow-up in he cu en s udy, only one o he 13 pa icipan s who had expe ienced ESGs showed symp om ecu ence (see Figu e 3). Howe e , some s udies ha e epo ed sudden gains esul ing in signi ican di e ences in he ea men ou come e en a 12- mon h ollow-up phases (e.g., Bohn e al., 2013; Hedman e al., 2014), whe eas he cu en esul s ailed o show a signi ican di e ence a e 12 mon hs. Al hough ewe s udies ha e been published ocusing on he long- e m e ec o ESG han hose ocusing on he immedia e e ec , hese indings suppo he iew ha changes in symp oma ology e y ea ly in he ea men p edic s able and signi ican imp o emen s. In addi ion, ESGs appea o indica e a e y low a e o symp om ecu ence e en when he ea men is deli e ed by no ice he apis s. I may be impo an o include egula assessmen in he ea ly phase o he ea men o cap u e and o ake ad an age o ESGs. I has been epo ed elsewhe e, ha a ound 60-70 % o hose pa icipan s who ook pa in he cu en s udy bene i ed o he six sessions ACT in e en ion (omi ed om he masked manusc ip , 2018). These esul s sugges ha almos hal o hose pa icipan s who bene i om a six-session ACT in e en ion deli e ed by no ice he apis s, bene i a e only wo sessions. Howe e , u he esea ch is needed o examine whe he a e y sho ea men could be su icien on i s own o a subg oup o pa icipan s wi h dep ession symp oms o i i is impo an o con inue he ea men a e ESG is obse ed o ensu e he s abili y o he changes. Fu he esea ch is also needed o unde s and i i could be possible o p omo e sudden gains o ea ly sudden gains. P e ious esea ch has no been able o consis en ly associa e sudden gains wi h a ce ain me hod o session con en . In e es ingly, high he apeu ic compe ence and long clinical expe ience do no appea o be necessa y o ESGs o occu , ei he . In ac , he limi ed aining ime and he absence o clinical expe ience among he no ice he apis s who p o ided he ea men in he cu en s udy did no seem o signi ican ly educe he equency o sudden gains MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT compa ed o he equency epo ed in s udies ha did use mo e expe ienced he apis s. Gi en ha ESGs p oduce long-las ing e ec s, i would be highly bene icial o be able o in en ionally acili a e sudden gains. Fu he mo e, knowledge o he p ocesses associa ed wi h ESGs could be u ilized o c ea e mo e e ec i e ea men p ocedu es i u he esea ch we e able o iden i y ac o s esponsible o he ea ly sudden gains. The occu ence o sudden gains in a ious se ings sugges s ha sudden gains a e no speci ic o ce ain popula ions, ea men s, o se ings and no a e hey consis en ly ela ed o any o he demog aphic o psychological measu es used ac oss sudden gain s udies. In ac , he e is no s ong e idence o suppo any o he hypo heses p esen ed o explain sudden gains. Indi idual s udies ha e associa ed sudden gains wi h ce ain me hod- ela ed ac o s (e.g., cogni i e changes; Tang & DeRubeis, 1999) o demog aphic ac o s (e.g., pa icipan age; Kelly e al., 2005), bu none o hese esul s ha e been eplica ed o widely suppo ed by o he s udies. A his momen , sudden gains emain unexplained, and some s udies ha e e en sugges ed ha sudden gains could be ela ed o some o he common ea u es o psychological ea men s (Kelly e al., 2005). The e o e, u u e esea ch on sudden gains and possible ac o s ha could explain sudden gains could ha e an in e es ing ole in u he ing he unde s anding o c ucial p ocesses in psychological in e en ions. I is impo an o be awa e o he ollowing limi a ions when gene alizing he esul s o he cu en s udy. Fi s , he sample ha was in es iga ed was small, and 23% o pa icipan s we e los a he ollow-up phases. The pa icipan s who did no ind he in e en ion help ul may ha e declined pa icipa ion in he ollow-up mo e o en han hose who expe ienced he in e en ion as e ec i e, c ea ing he possibili y o a biased sample. Second, he in e en ion was deli e ed by no ice he apis s wi h only ou days o aining. This may cause a ia ion in he compe ence le els o he he apis s causing mo e be ween-subjec a ia ion han migh be expec ed in da a wi h expe ienced he apis s. Thi d, mos o he pa icipan s we e women, and all we e olun ee s who we e mo i a ed o ake pa in he in e en ion. This limi s he sample’s ep esen a i eness MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT compa ed o clinical popula ions in gene al. Follow-up ime was ela i ely sho (12 mon hs). Also, he in e en ion was con inued a e ESG was obse ed. Thus, mo e s udies a e needed in es iga ing he main enance o ea men e ec s a e ESGs wi hou any u he ea men . This knowledge would help wi h he u iliza ion o he p ognos ic alue o ESGs, and i could also help wi h he de elopmen o e ec i e b ie in e en ion models. In addi ion, ollow-up designs ha con ol o possible ea men du ing he ollow-up pe iod a e needed o d aw u he conclusions ega ding he long- e m e ec s o ESGs. In conclusion, he cu en esul s suppo he hypo hesis ha ESGs in an ACT in e en ion yield s able imp o emen s in dep ession symp oms and psychological lexibili y, which can be iden i ied up o 12 mon hs a e ea men . Though p elimina y, he esul s sugges ha no ice he apis s can p oduce ESGs wi h e y li le aining among app oxima ely 20–25% o he clien s. The indings add o he body o esea ch ha sugges s ha changes ea ly on in an in e en ion can be used as a p ognos ic ool on an indi idual le el. Acknowledgemen s Omi ed om blinded e iew. Re e ences Ade ka, I. M., Appelbaum-Namda , E., Sha an, N., & Gilboa-Schech man, E. (2011). Sudden gains in p olonged exposu e o child en and adolescen s wi h pos auma ic s ess diso de . Jou nal o consul ing and clinical psychology, 79(4), 441. Ade ka, I. M., Nicke son, A., Bøe, H. J., & Ho mann, S. G. (2012). Sudden gains du ing psychological ea men s o anxie y and dep ession: A me a-analysis. Jou nal o Consul ing and Clinical Psychology, 80(1), 93-101. 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A b ie Accep ance and Commi men The apy in e en ion o dep ession: A andomized con olled ial wi h 3-yea ollow-up o he in e en ion g oup. Jou nal o Con ex ual Beha io al Science, 10, 55-63. MANUS CRIP T ACCEP TED ACCEPTED MANUSCRIPT Long- e m s abili y o ea ly sudden gains in an accep ance and alues-based in e en ion Highligh s Ea ly sudden gains a e associa ed wi h s able imp o emen s du ing a one-yea ollow-up. Pa icipan s who do no expe ience ea ly sudden gain achie e equal esul s a 12-mon h ollow-up. Ea ly sudden gains can occu in ea men s p o ided by no ice he apis s wi h li le aining. Ea ly sudden gains a e a clinically impo an sub ype o imp o emen .