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This stud y exam in ed the anx iety and pa in reports in a group o f sub jec ts du ring a stim u-la tio n experim ent in w hich the sub jec ts w ere m isin form ed tha t an e lectrica l curren tw a s be ing conducted through elec trod es a ttach ed to th e ir head s. Th e experim en ts pu r-po se w as to de term ine how th e subjec ts reportin g o f pa in w a s rela ted to the ir report-ing o f anx ie ty over tim e . O ne subset o f the sub jec ts ra ted pa in only , a second ra tedpa in and anx ie ty , a nd a th ird ra ted pa in and hunger. The three g roups d id not d iffersig n ifican tly in the frequency or in tensity o f the ir pa in repor ts. Th e separa te ra tingsfor bo th anx ie ty and pain increased in a para llel m anner. These resu lts , how ever, d onot support th e theor ies invo lv ing the suppress ion of aw a reness o f a ffec t in som a to fomdisorders .

41 6 PSYCHOSOMAT IC S

Anxie ty in E xp er im en ta lly Indu cedSom ato fo rm Sym p tom s

T IMOTHY L . BAYER , M.D . , EL IZA BET h CH IA NG , M.D .J oi- m 1 H . COVERDALE , M.B . , CH .B ., M ARK BANG S , M.D .

HAROLD GOODEARLE

Individuals v ary w ide ly in the w ay tha t theyp erceiv e and repo rt ph ysica l sym p tom s . P a r-

ticu lar ly troub lesom e exam p les o f th is v a ria tionare p a tien ts w ith som a to fo rm d iso rd ers , w hocom pla in o f sym ptom s w hen dem on strab lephy sical les ions are absen t. F o llow -u p stud ieshave sh ow n tha t the se d iso rde rs are frequ en tlym isd iagno sed .2 Fu rth erm ore , som a tizin g pa -tien ts accou n t fo r a sig n ific an t po rtion o f m ed-ica l ca re co sts .3

A nx ie ty and sym p tom rep orting h ave beenc lose ly lin ked in stud ies o f acu te pa in in clin ica l

Receiv ed D ecem ber 3 1 , 19 91 ; rev ised Feb rua ry 21 ,1992 ; accepted June 17 , 1992 . F rom th e D ep artm ent ofPsych iatry and Behav io ra l S c iences , B ay lo rC ollege of M ed-icine, H ous ton, TX 77030. Dr. Cove rdale is currently sen iorlec tu re r in the D epartm en t o f P sych ia try an d B ehav io ra lSc iences, U n ive rsi ty o f Auck land Schoo l of M ed icine,Auck lan d , N ew Zea land . A dd ress rep rin t requests to D r.B ayer, D epartm en t o f P sych ia try , 1 B ay lo r P laza , H ouston ,TX 77030.

Copyrigh t 1993 The A cad em y of Psychosom aticMed ic in e .

se ttin gs and p ain ind uced b y phy sica l s tim u-la tion in exp erim en ta l se ttings .4 H ow eve r , there la tionsh ip b etw een an x ie ty and sym p tom re-po rting in the som a to fo rm d iso rde rs is lessclea r. M ech an ic5 n o ted tha t in som e fo rm u la-tions o f the som a tizatio n p ro cess , the p atien t isaw are o f the stre ss and accom pany ing an x ie ty .In o the r fo rm u la tion s, such as in co nve rsiond iso rde rs , the sym ptom rep lace s aw aren es s o fthe stress , an d the p atien ts w ill deny any an x ie tyo r s tre ss . F u rthe rm ore, s ev era l au tho rs h av esu gg ested tha t som a to fo rm sym ptom s w ill b em ore lik ely to occu r in ind iv idu als w ith an im -pa ired ab ility to a ttend to an d d esc r ibe the irp sycho log ica l d is tress .6 7

A n ea rlie r s tud y , w h ich w e design ed top ro duce p ain in th e ab sence o f phy sical s tim u-la tion , w as cond uc ted to deve lo p a m ech an ismfo r tes ting th eo rie s abo u t the som a tiza tion p ro -ce ss .8 T he sub jec ts in th is ea rlie r s tu dy w ere ledto be lieve tha t a stim u la to r (a fac sim ile o f agene ra to r) w as passing e lec tr ica l cu rren tth ro ugh th eir head s, su ffic ien t to cause a h ead -

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ache . A lthou gh no cu rren t w as transm itted ino u r ex pe rim en t, m ore th an h alf o f the sub jec tsrepo rted pa in .

A lthou gh anx ie ty is like ly to p lay a ro le inth e d eve lopm en t o f pa in from s tim u la tion , w ed id n o t a sk the su b jec ts to rep o rt fea r o r an x ie tyin ou r p rev ious stu dy8 becau se d o ing so co u ldin fluen ce the ir pa in repo rtin g . Th e stim u la to rand th e w arn ing o f pa in w ere like ly to p rod uceu ncom fortab le in terna l s ta tes tha t th e sub jec tsco u ld have labe led as fea r, p ain , o r b o th . B e-cause pa in w as m ade m ore salien t b y th e ex pe r-im en tal in s tru ctio ns, pa in w as like ly to b ech osen and fear m ay have been m is lab eled aspa in . H av in g the su b jects ra te an d labe l an x ie tym ay lead to its selec tive m on ito r ing and the re -fo re cou ld dec rea se pa in ra ting s. T h is co u ldoccu r e ithe r because th e ratin g o f an x ie ty p ro -v ide s a d is trac ting cogn itive schem a or becau seit p ro v ide s a m ore accu rate schem a by h elp ingsu b jec ts to d iffe ren tiate be tw een fear and pa in .9

T he pre sen t s tud y used th ree expe rim en ta lg ro ups to de te rm ine w h eth e r p rov id ing e ithe r ad is trac ting task o f ra ting o the r sta tes , o r a m orere levan t task o f ra ting anx ie ty w ou ld d im in ishpa in repo rtin g du ring false stim u la tion . T hepa in ra ting o n ly g roup w as w arned of pa in andrece ived stim u latio n in a m ann e r sim ilar to thep rev iou s stud y . T hey w ere no t ask ed to auendto an y th in g o th e r than p ain du ring stim u la tion .Th e an xie ty + pa in ra ting g rou p ra ted th e ir lev elo f anx ie ty o r fear a t add itio na l in te rv als tha ta lterna ted w ith th e p ain ratin g in terva ls d u rin gstim u la tion . T he hun ge r + pa in ra ting g roupra ted h ung e r du rin g add itio na l in te rv als .

W e hypo thesized tha t 1 ) the hun ge r + painra ting g rou p w ou ld repo rt le ss pa in th an the pa inra ting o n ly g ro up b ecause they w ou ld b e m on i-to r ing com pe ting in te rna l cu es , and th at 2 ) theanxiety + pa in ratin g g roup w ou ld repo rt lesspa in th an the h ung er + pa in ra ting g roup b e-cau se th ey w ou ld be m on ito rin g re levan t com -pe ting cues. D e te rm in ing w h e the r th e p rocesso f ra ting anx ie ty alte rs su bsequen t p ain rep o rtsis an is sue tha t m ust b e c la rif ied b efo re there la tion sh ip be tw een anx ie ty and th is fo rm o fexpe rim en ta lly ind uced som a to fo rm p a in canbe exam in ed . B eyon d these m e thod o log ical

co ncerns, th is qu es tio n also h as c lin ica l im -p lic atio ns. If a tten tion to and labe ling o f anx ie tyreduces the tend en cy to som a tize, th is cou ldsu ggest c lin ica l in te rv en tions ap p licab le to pa -tien ts w ith som a to fo rm d iso rd e rs .

I f a tten tion to an x ie ty d id n o t a lter pa inrepo rts , w e p lann ed to co rrela te p ain rep o rtsw ith anx ie ty repo rts . T he sub jec ts w ho repo rtpa in w ou ld repo rt less an x ie ty if they ex ch an geaw areness o f pa in fo r aw areness o f anx ie ty , o rif aw aren es s o f an x ie ty is rep res sed in th e p ro -ce ss o f sym ptom fo rm a tion . If anx ie ty rep o rtsw e re no t d ec reased in sub jec ts w ho repo rtedpa in , w e p lan ned to ex am ine how rep orts o f thetw o sta te s w ou ld be tem pora lly re la ted .

M E THOD S

In the stu dy , 99 m en and w om en be tw een theag es o f 2 0 and 5 0 w ere rec ru ited w ith p ub licse rv ice ad ve rtisem en ts and w ith flie rs d is tr ib -u ted a t labo r po o ls and un em ploym en t o ffic e s .O f a ll the in d iv id ua ls w ho in qu ired ab ou t thestudy , 78% (9 9) chose to pa rtic ipa te , in c lu d in g77% (8 1) o f the m en and 8 0% (18 ) o f thew om en . A ll su b jects w e re in fo rm ed in advanceo f the ex posu re to pa in ; all gave w ritten consen t.E ach w ere pa id $ 20 . T he p rocedu re s fo llow edw ere in acco rdan ce w ith th e e th ica l s tanda rds o fth e local In stitu tion a l R ev iew B oard on H um anExp erim en ta tion . Th e sub jec ts w e re ran dom lyassign ed to one o f th e th ree g rou ps desc r ibedearlie r by u sing a lis t o f ran dom num bers .

T h e m ean standa rd e rro r (SE ) ag e o f thesam ple w as 31 .2 0 .78 8 y ea rs; 82% (81 ) w erem en and 18% (18 ) w ere w om en . T he m a jo rityo f sub jec ts w e re b lack (5 9% , 58). T he re st w e rew h ite (27% , 27 ), H isp an ic (10% , 10) , and A sian(4% , 4 ) . F o r the g ro up , (57%, 56 ) were s ing le ,(22% , 22 ) w ere m arr ied , and (21% , 21 ) w eresep ara ted o r d ivo rced . T he ir m ean h igh est leve lo f educa tion w as 13 .1 0 .2 42 yea rs , an d 3 4%(34 ) o f them w ere cu rren tly em ploy ed . T heth ree g rou ps d id no t d iffe r s ig n ific an tly on anyof th e se v ariab le s .

T h e sub jec ts w e re sea ted in a cha ir facin gou r fake stim u la to r , w h ich w as co nstruc tedfrom a sou nd gen era to r tha t had been re labe led

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sh ock gen era to r. Tw o e lec trodes w ere a t-ta ched su p rao rb itally to th e ir head s w ith w ire slead ing to in ope rativ e lead s o n the gene ra to r .T he sub jec ts w e re to ld tha t an und e tec tab leelec tric a l cu rren t w ou ld pass th ro ugh th e irh ead s tha t cause s n o ha rm bu t the stim u la to rp ro duced a 1 0-H z no is e from a sp eak er a t theg en e ra to rs side , at an am p litude jus t au d ib leabo ve the back groun d no ise . A 7 .5 -cm diam e te rd ial on th e fro n t o f the stim u la to r , v is ib le to thesu b ject, w as se t in itia lly a t 1 0 an d w as in c rea sedin sca le inc rem en ts of 1 0 eve ry 5 m inu tes un tilit re ached a se tting o f 5 0 o n the d ia l. E achinc rease in the d ia l w as accom pan ied by a 10 -H z in c rea se in no ise frequen cy .

A com pu te r m on ito r fac ing the sub jec t d is-p lay ed a h orizo n ta l line fo r ra ting p ain labe ledin u n it in terva ls from 0 to 1 5 . B y horizon ta lm ovem en t o f a free -flo atin g joy stick leve r , th esu b ject m oved an a rrow ben ea th the ho rizo n ta lline to ind ica te the ir lev el o f p ain . A ratin g o f 0ind icated n o pa in . Th e sub jec ts w ere in s tru ctedto ra te p a in at 1 0 (the ana lge sic th resho ld ) w henth ey w ou ld no rm a lly tak e asp ir in o r sim ila rm ed icatio ns fo r p ain and a t 1 5 if th e p ain be -cam e so seve re tha t they cou ld n o lon ge r to le r-a te it. T he line ex ten ded bey ond a ce rta in p o in t(un labe led ) to in d icate tha t pa in beyo nd th isratin g w ou ld b e poss ib le . H ow eve r, th e su b jec tsw e re to ld tha t they w ou ld no t be ask ed to endu reth is h igh er leve l o f pa in . F o r each o f the fiv estim u la to r se ttings , each su b ject h ad s ix 20 -sec-o nd pe riod s in w h ich to ra te p a in . E ach 20-sec-o nd pe rio d fo r ratin g pa in co nsis ted o f an8 -second prep ara to ry pe rio d and a 12 -secon dp eriod fo r en te rin g the p ain ratin gs usin g th ejo ystick . T he p repa ra to ry pe riod w as s ig na ledb y a ton e, and m essages w ere d isp layed on th ecom pu ter m on ito r read in g p rep are to ra tepa in and p rev io us pa in ra ting w as ,,,,,.A fter th is 8 -secon d p repa rato ry pe rio d , th e ho r-izon ta l line w as d isp layed b eneath a m essag eread ing ra te p ain now . Th e su b jec ts cou ldth en m ove the joy stick leve r to ind ica te the lev elo f p ain fo r 1 2 secon ds, and th e com pu te r sam -p led th e ir pa in ratin gs ev e ry 2 secon ds du ringth is p er io d.

Th e pa in ra ting pe riods a lterna ted be tw een

p e riod s w ith n o add itio na l ratin gs o r pe riods fo rra ting o f o the r in te rn al s ta te s . T hese a lterna tingp e riod s also la sted 2 0 second s. T he sam e jo y -stick leve r w as used to en ter a lte rn ativ e ra tin gsfo r th e an x ie ty + p ain ra ting g rou p an d the hu n-g er + pa in ra ting g ro up .

V e rtica l m ov em en t o f the lev er m oved ana rrow a lon g a v e rtic al lin e tha t also con ta in edsettin gs be tw een 0 and 15 . The su b jec ts ratin gh ung e r w ere in struc ted to u se a ratin g o f 10w hen they w ou ld norm a lly sto p an ac tiv ity toea t and a ra ting o f 1 5 if they cou ld no lo nge rto lera te the ir hu nge r . T he sub jec ts ratin g anx i-e ty w ere in struc ted to use a ratin g o f 10 fo r fearso seve re they no rm a lly w ou ld avo id sim ilars itua tions and a ra ting o f 15 fo r fear o f seve reth at they cou ld n o lo nge r to le ra te it. M essages,s im ila r to the m essages used du rin g the pa inra tings , w e re d isp lay ed on the m on ito r du ringth is pe riod . F o r the p ain ra ting o n ly g ro up , am essage read in g w a it w as d isp lay ed th roug h-o u t th e 2 0 -seco nd pe riod .

A t the en d of the 2 0 m in u te s o f stim u la tion ,th e stim u la to r w as tu rned o ff and the e lec trodesw ere rem oved . T he sub jec ts in a ll thre e group sth en re tro spec tive ly ra ted th e ir fea r d u rin g stim -u latio n u sing the Sp ielb erge r S ta te T ra it A nx i-e ty Inven to ry (STA I).#{1 76 }T hey a lso in d icated ona d raw ing o f a head w h ere they had exp e riencedpa in . To ch eck the re liab ility o f the p ain rep o rts ,th e sub jec ts w ere q uestioned ab ou t th e na tu re o fth e pa in th ey h ad p rev io usly rep o rted .

A ll sub jec ts th en com ple ted a qu estio nna iretha t a sked them how m uch th ey b elieved ab ou tw ha t they w ere to ld in the stud y . T he true n atu reo f the stu dy w as th en exp lain ed to them a longw ith the rea sons fo r the decep tion . T he su b jectsw ho repo rted p ain w ere to ld tha t m any o the rsub jec ts also exp erienced p ain .

A ll m ean v alu es are rep o rted w ith stan da rde rro r . T h e th ree g roup s w ere com pared to eacho the r fo r the depen den t v a riab le o f num ber o fsub jec ts repo rtin g p ain by ch i-sq ua re . AK rusk al-W a llis on e-w ay an aly sis o f va r ian ce(A NOVA ) w as used to com pare pa in in ten sityrepo rts am ong th e th ree g roup s. A repea ted m ea-su re s A NOVA w as used to ex am ine the pa inra ting s ov er tim e fo r g ro up d iffe ren ces and tim e

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TABLE !. P ain ra tin gs by g roupPain rat ings Anx i e t y + pa in H unger + painon ly group ratin g g roup rating group

(n=30) ( n=35) (n=34)M ean SE p ain ratin gsa 2 .87 0.72 3.31 0 .6 3 2 .71 0.64N um ber and percen tage o f sub jec tsrepor t ing an y pain 16 ( 53 .3% ) 22 (62 .9% ) 16 ( 47 .1% )M ean SE pain r atin gs o f th os e

repor t ing p ain 5 .3 8 0 .98 5 .27 0.7 3 5.75 0.8 6N um ber and pe rcentage o f sub jects

repor t ing p ain abov e an alges ic th resho ld 2 (6 .7% ) 4 (1 1 .4% ) 2 (5 .9% )a}( f lI5 l( W a ll1S one -w ay ANOVA : X 2 ( correc ted fo r tie s ) = 1.0 37 , NS ; SE = standard error.bX 2 l .76 ,df=2 ,NS

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d ifferences . If d iffe ren ces w ere no t fou nd be -tw een the anx iety ra ting g rou p an d the o the rg rou ps, w e p lann ed to exam in e P earson co rre-la tion coe ff icien ts fo r an x ie ty and pa in ra ting sfo r each o f th e ra ting in te rv als . T h e su b jectsw ere d iv ided in to tho se w ho repo rted pa in andtho se w ho repo rted no p a in an d repeated m ea-su re s A NOVA w as u sed to exam in e th e an x ie tyrep o rts and hu nge r rep o rts fo r d ifferences inpa in repo rtin g s tatu s and tim e d iffe rences.

R E SULTS

W ith the stim u la to r ac tiva ted , 55 (5 4 .5%) sub -jec ts repo rted pa in . A n ad d ition al 23 su b jectsm oved the jo ystick to in d ica te p ain a t som e tim edu rin g stim u la tion , bu t on post-expe rim en ta lqu es tio n in g den ied fee ling any pa in . F ou rteeno f the se ra ting s re su lted from in ad ve rten t m ov e-m en t o f the jo ystick . S ix su b jects ind ica ted pa info r m o re p ro long ed in te rva ls , b u t la ter den iedpa in , and th ree late r repo rted tha t they h ad ex -pe rien ced , an d w ere ra ting , som eth ing o the rthan pa in . T hese sym ptom s inc lud ed a d rym ou th , tig h tne ss in th e neck , an d a p u lsin gsensa tion . D ue to the eq u ivo cal na tu re o f th epa in repo rts , th ese sub jec ts ratin gs w ere no tinc luded in th e g rou p rep o rting pa in . O f tho sedesc rib ing p ain , 7 su b jects de sc ribed p ain o n lya t th e site o f the elec tro des, 7 m o re h ad pa in a ts ite s ex tend ing beyo nd the e lectrod e site , 1 1 h adpa in a t the e lec trod e site an d a t o the r n oncon tig -uou s site s , an d 2 8 had pa in on ly a t o the r site s .

Inc lud in g all sub jec ts , the m ean leve l o f

m ax im a l p ain rep orted d uring stim u latio n w as2 .97 0 .378 . T he m ean leve l o f m ax im a l pa info r on ly th ose sub jects w ho repo rted pa in w as5 .4 4 0 .480 . T ab le 1 sh ow s th e num ber o f su b -je cts r ep ort ing p ain , th e num ber o f su b jec tsrep o rting p a in ab ov e the ana lge sic th re sh o ld ,and the m ean m ax im a l pa in ratin gs fo r each o fthe ex pe rim en tal g roup s. T he th ree g ro ups d idno t d iffe r on an y of th e se m easu re s .

In F igu re 1 , the m ean pa in ra ting s fo r eachg rou p a re p lo tted o ve r tim e d uring stim u latio n .A 3 (g ro up) x 5 (s tim u la to r se tting ) repeatedm easu re s A NOVA ind ica ted sign ific an t in -c rea se s in pa in ra ting s w ith in creasin g stim u la-t ion [F (4 ,94)=7 .517 , P

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Pain ra ting on ly 35 .5 2 .8 7 35 .9 1.73Anxiety + pain rat ing 46.1 l.73a 34.2 3.13Hunge r+painra ting 38.6 2.7 3 36.1 1 .81

No te : 2 x 3 A NO VA : I nt er ac ti on ( pa in r ep or ti ngstatus x gro up) F (2 ,92) = 3.48 , P

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pa in rep o rts a t a ll in terva ls w ere co rre la ted w ithanx ie ty repo rts a t th e sam e in te rva ls . T hu s, bo thw ith in -sub jec t and be tw een -sub jec t re la tion -sh ip s w ere exam ined . T he pa in repo rts w e rethen sh ifted in sing le steps and co rre la ted w ithanx ie ty rep o rts e ithe r in p rev io us o r subseq uen tin te rva ls so th at fo r each sh ift on e pa in repo rtan d on e an x ie ty rep o rt w ou ld be d ropp ed , an dthe rem a in ing rep o rts w ou ld b e co rre la ted fo ra ll su b jects a t a ll rem ain ing sh ifted in te rv a ls .W ith each sh ift in on e d irec tion , ea rlie r anx ie tyra tings w ou ld th en be co rre la ted w ith p rog res -s ive ly la ter pa in ratin gs, g iv ing a m easu re o f there latio nsh ip b etw een an x ie ty and sub seq uen tp ain . W ith each sh if t in th e op pos ite d irec tion ,ea rlie r pa in ratin gs w ou ld be co rre lated w ithp ro g re ssiv e ly late r an x ie ty ra tings , g iv ing am ea su re o f the re latio nsh ip be tw een p a in andsu bsequ en t anx ie ty . W hen th is w as d on e, theu nsh if ted co rrela tion coe ffic ien t w as 0 .666 . A sra tings w ere sh if ted in eith er d irectio n , th e co r-re latio n coe ff ic ien ts g radu ally dec lined .

W hen the su b jects w ere asked to in d icateh ow m uch they b elieved (on a scale ran g ingfrom 0% to 10 0% ) abo u t w h at they w ere to ldd u ring the exp erim en t, th eir re tro spec tive m eanb elie f ra tin gs w ere 8 4 .6% at th e exp erim en tss tar t and 91 .4% at the en d . T he re w ere no d if-fe rences be tw een gro ups o r b etw een sub jec tsw ho d id o r d id no t repo rt pa in .

D ISCUSS ION

T his stu dy used an ex pe rim en tal s ettin g kn ow nto p rod uce p ain in the absence o f pe riphe ra ls tim u latio n to exam ine th e re latio nsh ip be tw eenanx iety and pa in repo rtin g . N eith er the d is trac t-in g ta sk o f ra ting hu nge r no r th e ta sk o f a ttend -ing to and ra ting anx ie ty s ign if ic an tly reducedp ain repo rts .

I t is po ssib le tha t d ifferences in pa in rep o rt-ing be tw een the g ro ups m ay have fa iled to reachsign ific ance becau se o f an inadequa te sam plesize . W ith re spec t to th e freq uency of pa in re -p o rts , u sin g the tab le s o f C ohen , w ith a to ta lo f 9 9 cases , an d requ ir ing an a lpha o f 0 .05 an da pow er of 0 .80 , it w ou ld have been possib le toach iev e an effec t s ize o f ap p rox im ate ly 0 .30 ,

w h ich C ohen de fin es a s a m ed ium effec t s ize . Itrem a ins p ossib le tha t a sm a lle r effec t m ay h av eb een m is sed . It is a lso po ssib le tha t o the r com -p arison s th at d id no t use th e en tire sam p le o fsu b jec ts , su ch as com parisons w ith in in d iv id ua lg ro ups , m ay also h ave in su ffic ien t p ow er be -cause o f the sm a ller sam ple size .

T h is stu dy used a ratin g sca le d iffe ren tfrom th e v isua l ana logu e scale comm only rec-omm ended fo r stud ie s o f pa in , pa r ticu lar ly fo ran alg es ic com parisons.2 The sca le inco rpo -ra ted an in terna l ve rba l ancho r po in t, th e ana l-ge sic th resho ld ,3 to de te rm ine the num ber o fsub jec ts w ho rep o rted pa in at lev e ls tha t w ou ldbe lik ely to com e to c lin ica l atten tio n . R ecen tstud ie s h av e d em onstra ted tha t sca les w ith in -terna l ancho rs have com parab le va lid ity 4 andtha t the ca tego rical sca les m ay be ad van tageou sfo r be tw een -sub jec t com pariso ns. A lth oug h re -po rting o f m ild pa in w as comm on am ong oursub jec ts , re la tive ly few of th em repo rted pa inab ov e the ana lge sic th resh o ld . F u rthe r stud ie so f th e ch aracte r is tics o f th ose su b jects w ho d e -ve lop m ore seve re pa in cou ld p ro v ide a b ette rm od el fo r the som a tizatio n p rocess than stud ieso f all sub jec ts w ith pa in .

T he sam ple o f sub jec ts rec ru ited fo r th iss tud y m ay have b een d iffe ren t from th e types o find iv idua ls w ho a re like ly to deve lop som ato -fo rm d iso rde rs . W om en a re d iagn osed w ith o neo f th e som a to fo rm d iso rde rs w ith g reate r fre -qu ency (e .g ., som a to fo rm p ain d iso rde r) o r a tlea st equ al frequ en cy (e .g ., hyp ocho ndria sis)w h en com pared w ith m en ,6 bu t few wom envo lu n tee red fo r th is s tud y . The pe rcen tages o fw om en an d m en w ho fa iled to take pa rt in thestud y a fte r in itia l con tac t w e re com parab le , b u tit is p ossib le tha t a g reate r p rop o rtio n o f w om enw ho h eard o f the stu dy fa iled to inqu ire abo u t itbecau se o f the adv an ce w arn ing o f pa in in thead ve rtis em en t. In a s im ila r s tu dy do ne o n ag roup of co llege stud en ts , s lig h tly m o re su b -jec ts repo rted pa in , w h ich m ay have re su ltedfrom th e la rge r num bers o f w om en in the su b jec tpoo l.7 Th is gend e r d iffe ren ce m ay also lim itan y conc lus io ns rega rd ing th e re la tionsh ip b e-tw een an x ie ty and p a in in th is s tu dy if the re a regende r d iffe rences in the som a tiza tion p rocess .

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A nx ie ty in E xperim en ta lly In duced Sym ptom s

42 2 PSYCHOSOMAT IC S

Fo r exam ple , G u sta fso n and K a llm en8 haved escr ibed gende r d iffe rences in m an ife st an x i-e ty in p atien ts d iagn osed w ith p sycho som aticb ody pa in .

The re m ay also be a sam pling b ia s b ecauseo f p erson ality d iffe ren ces in those w ho vo lun -tee r fo r exp e rim en ts invo lv ing pa in . V o lun tee rsfo r such stud ies have been no ted to have lessh ypo chon dria sis ,9 w h ich m ig h t su ggest tha tth ey deve lop p ain com p lain ts by m echan ism so the r th an those seen in the typ ica l som ato fo rmd iso rde r . P a in stu dy v o lun tee rs h av e also b eenn o ted to h av e a m o re ex te rn al locus o f con tro l2#{176 }th at m ay a lter the w ay they are in f luenced byth e a rtif ic ial s tim ula to r .

B ecause ra ting an x ie ty in th is s tu dy d id no tredu ce pa in repo rts , it w as rea so nab le to exam -in e the re la tionsh ip be tw een anx iety an d p ain inth ose sub jec ts w ho had rated bo th s tate s . W henth is w as d one in sub jec ts w ho repo rted p ain ,repo rts o f anx ie ty and pa in inc rea sed toge the r .In th e sub jec ts w ith ou t p ain , anx ie ty decreased .T h is app a ren t lin k be tw een anx iety an d pa inra ting s m ay b e confou nded by the regu la r in -creases in the stim u lato r se tting s, w h ich m ayhave d riv en bo th ra ting s by a d em and m ech a-n ism . The p ara llels m ay also be d ue to a ha loe ffect in w h ich ra ting s on o ne m easu re in flu -ence the ra tings o f the o the r. H ow eve r, becausethe re la tionsh ip b etw een h ung er an d pa in w asm uch w eake r , o th er facto rs a lso seem to b eop era tive in the link be tw een pa in and anx iety .

In th is ex pe rim en ta l s ettin g , sev era l p ossi-b le m ech an ism s fo r the d ev elo pm en t o f som a to -fo rm sym ptom s w ere no t con firm ed . T he re w asno sup po rt fo r con ve rs io n m echan ism s in w h ichpa in is subs titu ted fo r a ffect w ith e lim ina tion o fthe affec t. S ub jec ts w ith pa in rem a ined aw areo f an x ie ty . Th e re w as a lso no supp ort fo rhy po th eses su ggesting th at som a to fo rm sym p-tom s occu r m ore comm only in ind iv idu als w hoa re unab le to desc rib e o r rep o rt o n p sycho log i-ca l s ta te s . F ina lly , th is s tudy d id n o t su ppo rt am echan ism inv o lv in g an exchang e o f labe ls .T he pa in repo rts m ay still hav e rep re sen ted am islab elin g p henom enon in w h ich a lab el o fp ain is added to , ra the r than rep lace s, the labe lo f an x ie ty . A nx ie ty appea rs to f it w ith in the

pa in -re la ted cog n itive schem a ra the r than tofo rm a com pe ting schem a. Th is con fo rm s w ithlea rn ing exp lan atio ns fo r som a to fo rm pa in inw h ich p ain is repo rted in the p re sence o f anx ie tybecau se o f cond ition in g from pa irin g o f p ainan d anx iety in eve ry day life .2

In sub jec ts w ith pa in , pa in and anx ie ty w erem o st h igh ly re lated d u rin g the tem po ra lly c lo s-e st ra tin g pe riods and th e rela tion sh ip d eclin edw h en sh ifted to ea rlie r o r la te r p er iod s. T h isw ou ld a rg ue aga ins t th e hyp o these s th a t sugg esttha t pa in p ro du ces the anx ie ty o r tha t anx ie typ rodu ces th e pa in . H ow eve r , th e in te rac tio nsbe tw een the tw o sta tes m ay still hav e occu rredm o re rap id ly th an cou ld be de tected d urin g ourra ting in te rva ls . C orre la tions be tw een anx ie tyand pa in a lso inc rea sed o ve r tim e , w h ich w ou ldsugg est tha t the tw o sta te s re in fo rce each o the rin a rec ip roca l fa sh io n .

T he se tting o f th e study , w h ich inc lud edprom in en tly d isp lay ed m ed ica l equ ipm en t,c lo se ly pa ralle ls c lin ica l se tting s, and the p ainw arn ing is sim ila r to w arn ings d u ring the p ro -ce ss o f ob ta in ing in fo rm ed co nsen t in m ed ica lse ttin gs. T h is su ggests tha t e lem en ts o f the m ed -ica l s ettin g an d of th e in fo rm ed con sen t p rocessm ay them se lves m ak e p ain repo rts m ore lik ely .T h is on ly occu rs in som e ind iv idua ls , and fu r-the r resea rch m ig h t h elp to c lar ify w ho is m o stsuscep tib le to th is fo rm of su gg estio n .

T hese f ind in gs sup port a c lo se link b e tw eenanx ie ty o r fear an d psych o log ica lly indu cedpa in . C lose tie s be tw een the tw o sta tes havebeen d em ons tra ted fo r pa in o ccu rr ing w ithph ysica l s tim u la tion in c lin ica l and ex pe rim en -ta l se tting s,4 a lthou gh a recen t stud y has sug -gested tha t th is m ay no t o ccu r w h en th e anx ie tyis irrelevan t to th e pa in .22 Th is is the firs t tim etha t the re la tion sh ip has b een sh ow n in th e ab -sence o f p eriph era l s tim u la tion . Th ese f ind in gsdo n o t supp ort the use o f co gn itiv e stra teg ie sa im ed a t be tte r iden tif ica tio n and labe ling o fanx iety in o rde r to redu ce p ain repo rts . In fac t,ratin g anx ie ty d id n o t d im in ish pa in repo rtingbu t app eared to inc rea se anx iety repo rting . It ispo ssib le tha t o th er stra teg ie s , inc lud ing cog n i-tive s tra teg ie s a im ed a t redu cin g an x ie ty o r re-fram in g anx ie ty , m ay b e u se fu l.

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Baye r e t a !.

VOLUME 34. NUMBER S #{149}EPTEMBER - OCTOBER 1993 42 3

This stu dy w as supported b y the A lexP okorn y G rant from the D epartm ent o f P sych i-

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