Influence of general self-efficacy as a mediator in Taiji-induced stress reduction : results from a randomized controlled trial

Influence of general self-efficacy as a mediator in Taiji-induced stress reduction – Results from a randomized controlled trial

Marko Nedeljkovic

, Viviane Wepfer

, Brigitte Ausfeld-Hafter

, Petra H. Wirtz

, Konrad M. Streitberger

aUniversityofBern,InstituteofComplementaryMedicineKIKOM,Imhoof-Pavillon,Inselspital,CH-3010Bern,Switzerland

bUniversityofBern,BiologicalandHealthPsychology,DepartmentofPsychology,Alpeneggstrasse22,CH-3012Bern,Switzerland

cUniversityHospitalBern,DepartmentofAnesthesiologyandPainTherapy,Inselspital,CH-3010Bern,Switzerland

Abstract

Aimofthestudy: InthisstudyweexaminedtheeffectsofTaijionperceivedstressandgeneralself-efficacy(GSE),andinvestigatedthemediating roleofaTaiji-inducedGSEincreaseonTaiji-relatedreductionofperceivedstress.

Materialsandmethods: 70healthyparticipantswererandomlyallocatedeithertotheTaijiinterventiongrouporthewaitinglistcontrolgroup.The interventionlastedfor12weekscomprisingtwoTaijiclassesperweek.Before,shortlyafter,andtwomonthsaftertheintervention,weassessed thedegreeofperceivedstressandGSEinallparticipantsbyemployingthePerceivedStressScale(PSS)andtheGSE-Scale.

Results: Comparedtocontrols,participantsoftheTaijigroupshowedasignificantlystrongerdecreaseofperceivedstressandahigherincreasein GSEfrompre-topost-interventionassessment(PSS:p=0.009;GSE:p=0.006),aswellasfrompre-interventiontofollow-upassessment(PSS:

p=0.018;GSE:p=0.033).AmediatoranalysisbasedonamultipleregressionapproachrevealedthataTaiji-relatedincreaseinGSEstatistically mediatedthereductioninperceivedstressafterTaijiascomparedtobaseline.PosthoctestingshowedthatthemediatingeffectofGSEwas significant(p=0.043).

Conclusions: OurfindingsconfirmpreviouslyreportedTaiji-relatedstressreducingandGSEenhancingeffectswithGSEincreasemediatingTaiji relatedreductionofperceivedstress.

Keywords: Taiji;Generalself-efficacy;Perceivedstress;Randomizedcontrolledtrial;Mediatoranalysis

Introduction

Chronic stressful experiences predispose to the develop- mentofmaladaptivechangesinphysiologicalstressresponsive systems and healthbehavior known for their harmful impact on healthand longevity [1–3]. Longitudinal and experimen- tal studieshaveshownthat perceived chronic stress playsan importantroleinpathogenesisofvariousphysicaldiseasessuch as acuterespiratory infection [4], cardiovasculardisease [5], anddelayedwoundhealing[6],aswellasofmentaldisorders

∗Correspondingauthor.Tel.:+41316329758;fax:+41316324262.

E-mailaddresses:marko.nedeljkovic@kikom.unibe.ch(M.Nedeljkovic), viviane.wepfer@students.unibe.ch(V.Wepfer),

brigitte.ausfeld-hafter@kikom.unibe.ch(B.Ausfeld-Hafter), petra.wirtz@psy.unibe.ch(P.H.Wirtz),konrad.streitberger@insel.ch (K.M.Streitberger).

includingdepression,alcoholism,generalizedanxietydisorder or phobia[7–9].Hence, the investigation of stress protective interventions is of high relevance for health maintenance or promotion.

Taiji is a mind-body practice that has received increased attentioninwesternsocieties[10]aswellasintheresearchcom- munityasapotentialinterventionforstressmanagement[11].

TaijiisrootedinChinesemartialartsandischaracterizedbythe flowofgentleandmindfullyperformedbodymovements.Taiji practiceaimstostrengthenandrelaxbothbodyandmind, as wellastoenhancepersonaldevelopmentandself-defence[12].

Despitesomenon-significantfindings[13–16]thecurrentstate of researchgenerallysupportsstress-reducing effects of Taiji suchasdecreasingperceivedstress[11,17–26],andattenuating psychophysiologicalstressreactivity[27,28].However,investi- gationsrelatedtotheunderlyingstressprotectivemechanisms ofTaijiarestillscarce[26].

Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-0-276568 Erschienen in: European Journal of Integrative Medicine ; 5 (2013), 3. - S. 284-290

Self-efficacyisdefinedas the confidenceinone’scapabil- itytomasterademandingsituation[29].Perceivedself-efficacy influencesbehavioraswellascognitive,motivational,andemo- tionalprocessesinsubjectivelydifficultevents[30].Theconcept of confidence in one’s coping abilities can be related to a specific domain (specific self-efficacy) as wellas more gen- erallytoavarietyof stressfulsituations(generalself-efficacy –GSE)[31].Positiveeffects ofTaijiondomain-specificself- efficacyhavebeenrepeatedlyobserved,namelyonself-efficacy relatedtoexercisebehavior[19,32–35],painmanagement[36], physicalcapability[37]andfallprevention[34,38].Asignif- icant increase in GSE following Taiji has been reported in three randomized controlled trials [39–41]. The notion that GSE is likely to mediate stress reducing treatment effects is supportedbythecognitivetransactionalstresstheory[42,43].

According tothistheoretical approach GSE playsakey role intheappraisalprocessinpotentiallystressfulsituations.The greater self-efficacy, the more likely a stressful encounter is interpretedas achallenge andless likelyas a threat [44].In line with this reasoning the association of higher levels of GSEwithalowerdegreeof perceivedstresshasbeenrepeat- edlyfound in priorresearch [44–49]. Moreover,a mediating effect of GSE on the perception of psychological stress has beenpreviouslyreported[45,50].However,amediatingeffect of a GSE increase on the reduction of perceived stress in response toregular Taijipractise has notyet been examined.

WethereforesetouttoinvestigateinafirststepwhetherTaiji increases general self-efficacy (GSE) and reduces perceived stress. In a second step, we assessed whether a Taiji-related increaseinGSEpotentiallymediatesstressreductionfollowing Taiji.

Methodsandmaterials Participantsanddesign

Thisstudywaspartofatrialinvestigatingpsychobiological effectsofTaijionpsychosocialstressreactivityinhealthypar- ticipants[27]. Formalapproval was obtained from the ethics committee of the Canton Bern, Switzerland. Recruitment of studyparticipantswascarriedoutthroughadvertisementofthe studyonpinboardsandonthehomepageattheUniversityof Bern,andattheUniversityHospitalinBern.Throughtelephone screening, healthyapplicants aged from18 to 50yearswere includedand,iftheexclusioncriteriadidnotapply,randomly allocatedeithertotheTaijiinterventiongrouportothewaiting listcontrolgroup.Detailedinformationaboutexclusioncrite- riaandtherandomizedgroupallocationarereportedelsewhere [27].

Taijiintervention

TheTaijicoursestartedinSeptember2010andlastedfor12 weeks. Trainingsessions of 60min tookplacetwice aweek.

A certified Taiji teacher, awarded by the Swiss Society for QigongandTaijiquan(SchweizerischeGesellschaftfürQigong und Taijiquan – SGQT), was in charge of all Taiji classes

and recorded participants’ course attendance. Participants in the Taiji group were taught the first 18 sequences of the 37 ChenMan-Ch’ingYang-StyleTaijishortform[10]byempha- sizingbasicTaiji principlessuch asextension,relaxationand alignment of the body, as well as holistic and mindful body movements [51]. Eachtraining sessionstarted withwarm-up exercises (15min), followed by practicing Taiji movements and reviewingthe above mentioned basicprinciples(35min) andendedwithTaijirelatedbreathingandrelaxationexercises (10min).Participantsof bothstudygroupswereaskednotto takepartinanynewmind-bodyorphysicalexerciseprogram duringtheirstudyparticipation.Aftercompletionofthestudy,an equivalentTaijicoursewasofferedtoparticipantsinthecontrol group.

Measures

PsychologicalstresswasmeasuredbythePerceivedStress Scale(PSS)[7].This10-itemself-reportquestionnaireassesses participants’ cognitive evaluation of stressfulness of the sit- uations experienced in the past month of their life. Items weredesignedtoestimateonafivepointLikertscaleranging from “never” to “very often” how unpredictable, uncon- trollable, and overloaded participants perceive their lives.

Good internal consistency is reported (Cronbach’s α=0.78) [7].

GSEwasmeasuredbytheGeneralSelf-EfficacyScale[31].

This10-item scaleassessesageneralsenseof perceivedself- efficacy withthe aim to predict copingwith dailyhassles as wellasadaptationafterexperiencingstressfullifeeventsingen- eral.Eachitemreferstosuccessfulcopingandhastoberated regardingitsaccuracyonafourpointLikertscalerangingfrom

“notatalltrue”to“exactlytrue”.Internalconsistencyisconsid- eredtobehighwithCronbach’sαvaluesrangingfrom0.86to 0.94[52].

Procedure

Completeoralandwrittendescriptionofthestudywaspro- videdtoallincludedparticipantsandinformedwrittenconsent wasobtainedpriortoparticipation.Atpre-interventionassess- mentpriortogroupallocation,participantscompletedanonline surveycomprisingthePSSandtheGSEquestionnaires,along- sideotherquestionnairesnotrelevanttothepresentstudy.All study participants were asked to complete post intervention assessmentshortlyaftertheTaijicourse(week12)andfollow-up assessmenttwomonthsaftertheintervention(week20).Partic- ipantsnotresponding within5days wereremindedbyphone callandemail.

Statisticalanalyses

Dataanalysiswasconductedbyusingthestatisticalsoftware packageSPSS (version18)forMacintosh(IBMSPSS Statis- tics, Somers, NY, USA). All analyses were two-tailed, with the level of significance setat p<0.05. Unless indicated,all resultsarepresentedasmean±standarddeviation(SD).Prior

Table1

Groupcharacteristicsandbaselinevalues.

Groupcharacteristics^a Taijigroup(n=28) Controlgroup(n=31) p^b

Age(years) 35.86±8.64 35.13±6.53 0.74

Gender(male/female) 10/18 10/21 0.79

Bodymassindex(kg/m²) 23.38±3.31 23.11±3.57 0.79

Education(with/withouthighschooldegree) 21/7 25/6 0.76

Occupationalstatus(fullorparttimeworkers/students) 25/3 30/1 0.34

Smoking(non-smokers/lightsmokersi.e.<5cigarettesperday) 23/5 24/7 0.75

Previousexperiencewithmind-bodypractices(monthsofregularpractice) 15.79±29.98 30.04±45.10 0.21

Taijiclassesattended(incl.%-value) 20.8±2.97(86.8%) – –

Baselinevalues

PSSscore 17.07±5.30 17.61±5.83 0.77

GSEscore 29.18±3.19 27.97±4.02 0.21

aContinuousdataareexpressedasmean±SD

b p-Valuesrefertoχ²testsforcategoricaldata,andindependentsamplest-testsforcontinuousdataPSS,PerceivedStressScale;GSE,generalself-efficacyscale.

tostatisticalanalysesalldataweretestedfornormaldistribution andhomogeneityofvarianceusingtheKolmogorov–Smirnov andLevenetest.Groupcharacteristicswereanalyzedbyχ²-test forcategoricaldata,andindependentsamplest-testforcontin- uousdata.Groupdifferencesinbaselinevalueswerealsotested usingt-tests.

To examine the impact of Taiji on perceived stress and GSE we calculated repeated measures ANOVAs with group (Taiji vs. control) as the independent variable and repeated measures of perceived stress and GSE respectively as dependent variables. Post hoc analyses were conducted to test whether the study groups significantly differed in their mean change values from pre to post intervention assessment, as well as from pre intervention to follow-up assessment by conducting independent samples t-tests. For F-tests, the effect size parameter Cohen’s f was calculated frompartialη²-values(effectsizeconventions:f:0.10=small, 0.25=medium,0.40=large)andfort-testsCohen’sdwascom- puted(effectsizeconventions:d:0.20=small,0.50=medium, 0.80=large)[53].

To test whether GSE increases following Taiji mediate reductionsinperceived stress,amediatoranalysisbasedona multiple regressionapproach [54]was conducted. Avariable is regarded to mediate the relationship between an interven- tion and an outcome if the following three conditions are confirmed:(1) the predictorvariable(Taiji vs.control group) predicts the outcome variable (i.e. PSS change from pre- to post-intervention/waiting), (2) the predictor variable pre- dicts the mediator variable (i.e. GSE change from pre- to post-intervention/waiting), and(3) both,the predictorandthe mediatorvariablepredicttheoutcomevariablewiththeeffect of thepredictorvariableontheoutcomevariablebeinglower than in condition 2 [54,55]. PSS and/or GSE baseline val- ues were included inregression analyses with the respective changescores(i.e.PSSchange(condition1),GSEchange(con- dition 2), as well as PSS andGSE change (condition 3)) to controlfortheir influenceontheoutcomevariableandonthe mediatorvariable,respectively.Thelevelofsignificanceofthe mediation effect was assessed post hoc by using the Sobel test[56].

Results

Of the 112 applicants, 70 fulfilled inclusion criteria and completed pre-intervention assessment. They were randomly assigned to either the Taiji group (n=35) or the waiting list control group(n=35). As11 participantsdiscontinued (Taiji group n=7/control group n=4), post-intervention measures wereobtained from28participants ofthe Taijigroupand31 participantsof the controlgroup. Oneparticipantinthe Taiji groupand onein the control group didnot attend follow-up assessment.Theirlastvaluewascarriedforward.

Groupcharacteristics

Nosignificantgroupdifferenceswerefoundwithrespectto age,gender,bodymassindex,education,occupationalstatus, smoking,orpreviousexperiencewithself-applicablemind-body practices.Neitherdidthebaselinevaluesforperceivedstressand GSEsignificantlydifferbetweenbothstudygroups(seeTable1).

Taijieffectsonperceivedstressandgeneralself-efficacy

Taiji training significantly loweredperceived stress scores [main effect Taiji: F(1/309.62)=3.88, p=0.054, partial η²=0.064,f=0.26;interactionTaijibytime:F(2/49.11)=4.67, p=0.011,partialη²=0.076,f=0.28]andsignificantlyenhanced GSE scores [main effect Taiji: F(1/241.80)=5.82, p=0.019, η²=0.093,f=0.32;interactionTaijibytime:F(2/15.36)=4.82, p=0.010,partialη²=0.078,f=0.29]ascomparedtothecontrol condition.

Posthoctestingrevealedasignificantlystrongerdecreaseof perceivedstressscoresfrompre-topost-interventionassessment (t=−2.69,df=57,p=0.009)aswellasfrompre-tofollow-up assessment(t=−2.43,df=57,p=0.018)intheTaijigroupcom- paredtocontrols.PosthoctestingofGSEshowedasignificantly higherincreasefrompre-topost-interventionassessmentinthe Taijigroup compared tocontrols (t=2.83,df=57, p=0.006) whichpersisted inthe follow-upassessment (t=2.19,df=57, p=0.033). Raw data, p-values and effect sizes are listed in Table2.

Table2

Changesinperceivedstressscoresandgeneralself-efficacyscores.

Variable Meanchangefrombaseline(±SD) p^a d

Taijigroup(n=28) Controlgroup(n=31) PSSscore

-Week12(postintervention) −2.75±3.53 +0.32±5.02 0.009 0.71

-Week20(follow-up) −4.57±5.12 −1.32±5.15 0.018 0.64

GSEscore

-Week12 +1.89±2.88 −0.10±2.52 0.006 0.75

-Week20 +2.46±2.30 +1.06±2.58 0.033 0.58

PSS,PerceivedStressScale;GSE,generalself-efficacyscale;andd,effectsizeparameterCohen’sd.

ap-Valuesrefertoindependentsamplest-tests.

Mediationeffectsofgeneralself-efficacyonperceivedstress

Fig. 1 depicts the mediational model for GSE. In accor- dance with the above reported findings, regression analyses showedsignificanteffectsofTaijipractice(predictor)onmean changevaluesofperceivedstressfrompre-topost-intervention assessment (outcome) (B=−3.25; s(=standard error)=1.05;

β=−0.36;p=0.003)(condition1),andonmeanchangevalues of GSE from pre-to post-interventionassessment (mediator) (B=2.11,s=0.71;β=0.37;p=0.004)(condition2).Theeffect ofpre-postchangesinGSE(mediator)onpre-postchangesin perceivedstress(outcome)wassignificant(B=−0.66,s=0.18;

β=−0.41;p<0.001)andpersistedwhenadditionallycontrol- lingforTaijipractice(B=−0.53,s=0.19;β=−0.33;p=0.007) (condition3). Notably,theeffectofTaijipractice onpre-post changes in perceived stress was no longer significant, when pre-postchangesinGSEwerecontrolled(B=−1.92,s=1.08;

β=−0.21;p=0.08).Posthoctestingrevealedthatthereduction ofperceivedstressfollowingTaijiwassignificantlymediatedby Taiji-inducedGSEincrease(z=−2.06;p=0.043).

Discussion

In the present randomized controlledtrial we investigated theimpactofTaijipractice onperceivedstressandGSE,and explored amediating role of GSE in Taiji-induced reduction of perceived stress.To the best of ourknowledge, thisisthe first study examining GSE as an underlyingstress protective mechanismofTaiji.WefoundthatthreemonthsofregularTaiji practice ledboth toasignificantdecrease of perceived stress andanincreaseofGSEinhealthyTaijinovicescomparedtothe

waitinglistcontrolgroup.Notably,theseeffectswereofmedium effectsizesandpersistedatleasttwomonthsaftertheinterven- tion.Ourregressionanalysesconfirmedtheassumptionthatan increase inGSE followingthe Taiji interventionsignificantly mediatestheobservedreductioninperceivedstress.

The observedsignificant attenuation of perceived stressin responsetoTaijiisinlinewithemergingreportsonstressreduc- ing effects induced by regular Taiji practice [11]. Since our trial was nestedwithin alargerresearch project investigating effects of Taiji practice on psychobiological stress reactivity, participants might have fostered high expectations regarding Taiji induced stressreduction. Duetothe waitinglist control designwecannotruleoutaconfoundinginfluenceofapotential expectancyeffect.Futurestudiesmayincorporateanadditional activecontrolinterventionthatislikelytoevokesimilarstress reducingexpectations.Itmightbespeculatedthatparticipants’

positive expectations and/or breathing exercises might have addedtothestress-reducingeffectsobservedinourTaijigroup.

However, Taiji is characterized by unique principles empha- sizingthedevelopmentofamindfulembodimentofeffortless stabilityandcalmnessinmotion.Theseprinciplesmighthave effectively been transferredto copingwithpotentially stress- fulencountersindailylife.[27]Toelucidatewhetherthestress reducing effectsobservedinourTaiji groupdifferfromother activitiesthat alsoinclude breathingexercises and/orpositive expectations,comparativeeffectivenessresearchisneeded.

The observed enhancement of GSE through Taiji practice is in accordance with prior research [39–41]. Considering all foursourcesofself-efficacy, i.e.performanceaccomplish- ment, vicarious experience, verbal persuasion and emotional arousal[29],weassumethatpositiveexperiencesofsuccessfully

Fig.1.Mediationalmodelforgeneralself-efficacyMediationalmodelforassociationsbetweenTaijiinterventionandperceivedstressasmediatedbygeneral self-efficacy.Valuesonpathsarepathcoefficientscores(standardizedβ).Pathcoefficientsoutsideparenthesesarezero-orderregressioncoefficientscores.Path coefficientsinparenthesesarestandardizedpartialregressioncoefficientscoresfromtheequationthatincludestheothervariablewithadirecteffectontheoutcome (condition3).PSSand/orGSEbaselinevalueswerecontrolledforinregressionanalysesincludingtherespectivechangescores.ns,notsignificant;*p<0.05;

**p<0.01;***p<0.001;z,z-valuederivedfromSobeltest.

accomplishedlearningobjectivesareverylikelytooccurduring Taijiclassesandprobablycontributethemosttoanincreasein self-efficacy.However,asothersourcesofself-efficacymayalso bepresentinTaijiinterventions,theirspecificcontributiontoa Taiji-inducedincreaseinself-efficacyremainstobeelucidated.

Moreover, transferability and usefulness of the Taiji course contentsintoparticipantsdailylivesneedstobeaddressedin futureresearch,astheseaspectsarelikelytoshedlightonthe processofhowself-efficacyexperience duringTaijiclasses is transferredandgeneralizedintoparticipants’dailylives.

Theperceptionofstressandtheuseofcopingstrategiesto dealwithstressfulencountersdependonsituationalandpersonal resourcefactors[42].ThesignificantassociationbetweenGSE andperceivedstressfoundinthepresentstudysupportstheidea thatGSEfunctionsasapersonalresourcefactorinfluencingthe appraisalprocessandthereforeexertinganimpactonperceived stress.OurmediationalmodelsuggeststhattheimpactofTaiji on perceived stress mayhavebeen duetoits effecton GSE, whichinturnaffectedperceivedstress.Asindicatedbyregres- sionanalyses,aGSEincreasemayactas amediatorbetween Taijiandperceivedstressreduction.Thismediationeffectmight havebeenevenstronger,ifamorestressmanagementspecific aspectofself-efficacysuchascoping-self-efficacywouldhave beentested[57,58].Itneedstobekeptinmindthat,sinceGSE andperceivedstresshavebeenmeasuredatthesametimepoints, itcouldbethatindividualswithahigherreductioninperceived stressaremorelikelytodevelopahigherlevelofGSE.However, thisalternativemediationalmodellackstheoreticalfoundation.

Based on the definition of Taiji as a multicomponent inter- vention, futurestudiesshouldalso considertoexamine other potentialTaijicomponents(e.g.musculo-skeletalfitness,mind- fulness,socialinteractions,imageryandbreathing)[12],aswell as otherpersonalresourcefactors(e.g.commitments,beliefs, optimism, and sense of control) [42] related tostress reduc- tion that mayfunctionas underlyingmechanismsof Taiji.In additiontotheabove-mentionedconsiderations,thefollowing limitations need to be taken into account. First, we did only controlforbaselinevaluesofGSEandPSSscoresbutnotfor potentiallyconfoundingfactorssuchassocialsupportthatmay causebothelevationofGSEandreductionofperceivedstress [47,58].Second,our datais exclusively basedon self-report, which raises the issue of potential biases causedby socially desirableresponsepatternsand/orothersystematicresponseten- dencies.Toimprovethevalidityofourself-reportdatainfuture researchmultipleinstrumentsandapproachesfordataassess- mentsuchasphysiologicaltestsandthirdpartyratingsshould beused.Third,asabsolutereliabilityoftheemployedquestion- nairesisnotwarranted,randommisclassificationmaycausethe observedassociationstoappearnotasstrong astheyactually are[55].Furthermore,astheeffectsofTaijipracticeonstress reduction andresourceactivationmaybesubstantiallydiffer- entinatriskpopulations,futureresearchonilland/orstressed populationneedtobeundertaken.

Themainstrengthofthisstudyisitsrandomizedcontrolled designwithatwomonthsfollow-upperiod.Moreover,baseline characteristicsofthetwostudygroupswerecomparable.Finally, ourresultswereobtainedamongasampleofhealthyyoungto

middleagedadultsandthusaremorebroadlygeneralizablethan clinicalresearchrestrictedtoselectedpatientpopulationsand olderagegroups.

Conclusions

Our results confirm Taiji-related stress reducing and GSE enhancingeffects.ByhighlightingtheroleofGSEasamediator ofTaijiinducedstressreduction,ourfindingsprovideprelimi- naryinsightintoonemechanismofhowTaijimaycontributeto mentalhealthpromotion.

Financialsupport

FundingforthisstudywasprovidedbyStiftungfürKomple- mentärmedizin,GottfriedundJuliaBangerter-RhynerStiftung andParrotiaStiftung(toMNandBA)andbytheSwissNational Foundation Grant PP00P1 128565/1 (to PHW). The funding sourceshadnofurtherrole instudy design;inthe collection, analysisandinterpretationofdata;inthewritingofthereport;

andinthedecisiontosubmitthepaperforpublication.

Conflictofinterest

Allauthorsdeclarethattheyhavenoconflictsofinterest.

Acknowledgement

WethankMALukasRiederforproofreadingthemanuscript.

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