Ledesman and Kumano

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Psycho-Oncology

Psycho-Oncology 18: 571–579 (2009)

Published online 20 November 2008 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/pon.1400

Review

Mindfulness-based stress reduction and cancer:a meta-analysis

Dianne Ledesma and Hiroaki KumanoÃ

1Department of Stress Science and Psychosomatic Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan

Abstract

Objective: This meta-analysis was conducted to investigate the eff ects of mindfulness-based

stress reduction (MBSR) on the mental and physical health status of various cancer patients.

Methods: Ten studies (randomized-controlled trials and observational studies) were found to

be eligible for meta-analysis. Individual study results were categorized into mental and physical

variables and Cohen’s eff ect size d was computed for each category.

Results: MBSR may indeed be helpful for the mental health of cancer patients (Cohen’s

eff ect size d 50.48); however, more research is needed to show convincing evidence of the eff ect

on physical health (Cohen’s eff ect size d 5 0.18).

Conclusion: The results suggest that MBSR may improve cancer patients’ psychosocial

adjustment to their disease.

Copyright r 2008 John Wiley & Sons, Ltd.

Keywords: cancer; oncology; eff ect size; meta-analysis; mindfulness meditation

Introduction

The diagnosis of an illness like cancer results in acomplex set of physical and psychological issues

that in turn may contribute to depression andanxiety in patients [1]. Twenty to twenty-fivepercent of cancer patients are thought to havemajor depression and the greater the physicaldisability and pain due to cancer, the morefrequent the depressive symptoms and syndromes[2,3]. Other illness sequelae, such as post-surgerycancer-related fatigue due to chemotherapy orradiotherapy, and sleep disturbance have also beenwidely reported [4,5].

Psychosocial oncologic interventions have pro-ven largely eff ective in improving the quality of lifeand coping abilities of cancer patients, and inreducing their emotional distress and feelings of isolation [6–9].

Among these psychosocial interventions, mind-fulness meditation has shown some efficacy inpromoting relaxation and reducing psychologicalstress. Mindfulness, based on Buddhist meditation,refers to a ‘particular way of paying attention’, or a‘moment-to-moment awareness’, where the subjectremains non-judgmental and accepting of thediff erent sensations, thoughts, and perceptions thatcross one’s mind [10]. It has similarly beendescribed as the non-judgmental observation of

the ongoing stream of internal and external stimulias they arise [11]. An operational working defini-tion of mindfulness off ered by Jon Kabat-Zinn is

that it is ‘the awareness that emerges throughpaying attention on purpose, in the presentmoment, and non-judgmentally to the unfoldingof experience moment by moment’ [12]. The most

commonly cited method of mindfulness trainingused in clinical populations is the mindfulness-based stress reduction (MBSR) program developedby Kabat-Zinn and colleagues [10]. The MBSRprogram, off ered by the Center for Mindfulness inMedicine, Health Care, and Society at the Uni-versity of Massachusetts Medical Center, is astructured, group-formatted, 8–10 week coursethat patients attend once a week for an averageof 2 and a half hours, with homework assignmentof 45 min per day, 6 days a week, and a whole-daysession within the training period [10,13]. The maincomponents of the program involve three mind-fulness meditation practices that include the bodyscan, which involves ‘sweeping’ through the bodymentally from feet to head; mindfulness of breath and other perceptions; and Hatha yogapostures, designed to develop mindfulness duringmovement [13].

Various literatures have already described theefficacy of MBSR on diff erent patient populations,citing reduced pain, distress and anxiety, andimproved mood [13–16]. Several reviews of theefficacy of MBSR on patient populations have alsobeen published [11,17–23]. Bishop [17], in his

review, while noting the inadequacy of availableliterature on MBSR-based interventions and theinherent methodological problems in many of

* Correspondence to:Department of StressScience and Psychosomatic

Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.E-mail: hikumano-tky@ umin.ac.jp

Received: 20 September 2007

Revised: 12 March 2008

Accepted: 1 May 2008

Copyrightr 2008 John Wiley & Sons, Ltd.



the published data, concluded that MBSR holdssome promise as a behavioral intervention [17].Similarly, Baer [11] concluded that mindfulness-based interventions may alleviate a variety of mental health problems for a variety of patientsand non-patients, and improve psychological

functioning [11]. A meta-analytic review conductedby Grossman et al . [18] showed that MBSR as abehavioral intervention for diff erent patient andnon-patient populations has a moderate eff ect inhelping a broad range of individuals cope withtheir clinical and non-clinical problems [18].Finally, a non-meta-analytic, systematic review byKabat-Zinn [15] underscored the health promotingeff ects of MBSR in complementing conventionalbiomedical treatment as a comprehensive healingapproach for cancer patients [19].

Yet despite the fact that several reviews have

been published, none have given any empiricalbasis for determining the efficacy of MBSR oncancer patients alone. This study, therefore,through a formal meta-analytic approach, aims toestablish a quantitative assessment of the healthbenefits that may be derived by cancer patientsafter undergoing an MBSR intervention, and addweight to current literature on cancer and mind-fulness that could not be provided by previousstudies.

Methods

The following criteria were required for inclusionin the meta-analysis: (1) must involve the use of MBSR intervention as a psychosocial interventionfor a period of 6–15 weeks, (2) must involve cancerpatients of any age, gender, or stage of disease, (3)must report at least one quantitative outcomemeasure (physical or mental health measure), (4)must be in English, (5) must have been published inor prior to 2007.

An electronic search using the following data-bases was done: Medline, Science Direct, Disserta-

tion Abstracts International, PsychInfo, PsychLit,Web of Science, CINAHL, and the CochraneLibrary. The following keywords were used: mind-

ful Ã, insight meditation, Vipassana, mindfulness-based, cancer, neoplasm, lymphoma, sarcoma, and carcinoma. Although our criteria necessitated pub-lications to be written in English, publications donein other countries, or published in other languagesbut with abstracts at least written in English, werealso searched. All retrieved studies and their citedreferences were inspected to ensure no studies weremissed. Studies included in eight mindfulness

meditation reviews that were retrieved were alsochecked. For conference presentations, the firstauthors of studies marked for inclusion werecontacted and copies of their published or in-pressmanuscripts were received. We also inquired of the

authors of any ongoing research and unpublishedmaterial.

Coding of descriptive factors of eligible studieswas done by the first author (D. L.), which wasthen verified by the second author (H. K.).

The eff ect of MBSR on health status measures

was separated into physical health and mentalhealth subgroups. Data from standardized andvalidated scales with established internal consis-tencies were included. Under the ‘mental health’subgroup, scales measuring anxiety, depression,stress, and the psychological components of qualityof life were included. Under ‘physical health’,physical parameters and symptoms (e.g. levels of immunity, dietary fat, hormonal indices), and thephysical component of self-report questionnaires(e.g. cardiopulmonary, gastrointestinal, or centralor neurologic symptoms) were included. To assure

uniformity, only immediate, post-intervention data(after a 6–15 week course) were used to calculatethe eff ect size. For studies that collected data on aseries of time points, only the data from the firsttime point (immediately post-intervention) wereused. All data were then entered into a MicrosoftExcels spreadsheet, with one spreadsheet for eff ectsize calculations and another for study descriptors.All decisions regarding the inclusion and computa-tion of data were agreed upon by both authors(D. L. and H. K.).

To calculate Cohen’s d eff ect size, formulasprovided by Wilson and Lipsey were followed[24]. The eff ect size was initially calculated bygetting the diff erence between the means (forrandomized studies the diff erence between theintervention and control groups; for observationalstudies the diff erence between post-treatment andpre-treatment scores), and dividing the diff erenceby their respective pooled standard deviations. Incalculating the final eff ect size in randomized-controlled studies, the diff erence between thecomputed post-treatment eff ect size and pre-treat-ment eff ect size per health measure per study groupwas determined since the patients’ baseline values

could have varied among studies [18]. To reducethe bias of one study contributing many eff ect sizesto the total calculations, eff ect sizes computed fromdiff erent scales within one study were averagedunder two constructs: mental health and physicalhealth [24]. Each study then contributed only oneaverage eff ect size under mental health, and underphysical health. In conducting the within-groupanalysis of observational studies (post-treatmentversus pretreatment scores), a global estimation of r5 0.7 was used as the correlation between scores,since correlation coefficients could not be deter-

mined for all scales [18]. All eff

ect sizes were thencorrected for small sample bias [24].The resultant average eff ect sizes were aggre-

gated across studies by computing for a mean eff ectsize weighted by the number of subjects, with

Copyrightr 2008 John Wiley & Sons, Ltd. Psycho-Oncology 18: 571–579 (2009)

DOI. 10.1002/pon

572 D. Ledesma and H. Kumano



T a b l e 1 .

D e

s c r i p t i v e f a c t o r s o f i n c l u d e d s t u d i e s

A u t h o r

Y e a r

N a

M e a n a g e

( y e a r s )

T y p e o f c a

n c e r

S t a t u s o f

c a n c e r

T r e a t m e n t s t a t u s

C o n c u r r e n t t r e a t m e n t

T y p e a n d d u r a t i o n o f

m i n d f u l n e s s t r a i n i n g

O u t c o m e m e a s u r e s

R C T :

H e r b e r t e t

a l .

2 0 0 1

1 5 7

5 0

B r e a s t

M i x e d b

E i g h t y - s e v e n i n a c t i v e t r e a t -

m e n t

C h e m o t h e r a p y , r a d i a t i o n , t a -

m o x i f e n

1 5 w e e k s ( b a s e d o n U M -

S R C p r o g r a m )

P H Y : b o d y m a s s ; 7 D D R - d i e t a r y f a t ,

c o m p l e x c a r b o h y d r a t e s , f i b e r

M o n t i e t

a l .

2 0 0 5

9 3

5 3 . 6

B r e a s t , g y n e c o l o g i c ,

h e m a t o l o g i c , n e u r o l o -

g i c , r e c t a l , o t h e r

M i x e d

S e v e n t y - f o u r i n a c t

i v e t r e a t -

m e n t

C h e m o t h e r a p y , r a d i a t i o n , t r e a t -

m e n t f o r s i d e e f f e c t s o r o t h e r

o u t p a t i e n t c a n c e r - r e l a t e d p r o -

c e d u r e s

8 - w e e k M B A T ( 2 a n d 1 /

2 h / s e s s i o n )

P S Y : d i s t r e s s , Q O L ( S C L - 9 0 - R ,

S F -

3 6 m e n t a l h e a l t h

c o m p o n e n t ) , P H Y :

S F - 3 6 p h y s i c a l h e

a l t h c o m p o n e n t s

S h a p i r o e t

a l .

2 0 0 3

4 1

5 7

B r e a s t

I n r e m i s s i o n

W i t h i n t w o - y e a r p

o s t - t r e a t -

m e n t

N o t s p e c i f i e d

6 w e e k s ( 2 - h s e s s i o n s ) ,

o n e 6 - h s i l e n t r e t r e a t

P S Y : s l e e p l a t e n c y , q u a l i t y o f s l e e p ,

f e e l i n g s u p o n a w a k e n i n g , t o t a l s l e e p ;

Q O L ,

p s y c h o l o g i c a l

d i s t r e s s

( P O M S ) , s e n s e

o f c o n t r o l ( S C I ) ,

a n x i e t y ( S T A T E )

, d e p r e s s i o n ( B D I ) ,

s e n s e o f c o h e r e

n c e ( S O C ) , w o r r y

( P E N N )

S p e c a e t

a l .

2 0 0 0

9 0

5 0 . 8

B r e a s t , o v a r i a n , p r o s -

t a t e , N

H L , m

e l a n o m a ,

e n d o m e t r i a l ,

c o l o n ,

c e r v i c a l , o t h e r

M i x e d



7 - w e e k M B S R p r o g r a m

( 9 0 m i n p e r s e s s i o n )

P S Y : m o o d ( P O

M S ) , s t r e s s ( S O S I

m e n t a l h e a l t h c o m p o n e n t ) , P H Y :

S O S I p h y s i c a l h e a l t h c o m p o n e n t s

N o n - R C T :

C a r l s o n e t

a l . c

2 0 0 3

4 2

5 4 . 5

B r e a s t , p r o s t

a t e

M i x e d

A t l e a s t 3 m o n t

h s p o s t -

s u r g e r y ; n o t c u r r e n

t l y b e i n g

t r e a t e d w i t h c h e m o t h e r a p y ,

r a d i a t i o n , o r h o r m o n e t h e r -

a p y ( e x c e p t t a m o

x i f e n / g o -

s e r e l i n )

E i g h t e e n p a t i e n t s u s i n g t a m o x -

i f e n


( 9 0 m i n / s e s s i o n ) ; 3 - h s i -

l e n t r e t r e a t a t w e e k 6 / 7

P S Y : Q O L ( E O

R T C

Q L Q - C 3 0 )

m o o d ( P O M S ) , s t r e s s ( S O S I m e n t a l

h e a l t h c o m p o n e n t s ) , P H Y : c o u n t s o f

l y m p h o c y t e s , W

B C , n a t u r a l k i l l e r

c e l l s , B c e l l s , T c e l l s

C a r l s o n e t

a l . c

2 0 0 4

4 2

5 4 . 5

B r e a s t , p r o s t

a t e

M i x e d

A t l e a s t 3 m o n t

h s p o s t -

s u r g e r y ; n o t c u r r e n

t l y b e i n g

t r e a t e d w i t h c h e m o t h e r a p y ,

r a d i a t i o n , o r h o r m o n e t h e r -

a p y ( e x c e p t t a m o

x i f e n / g o -

s e r e l i n )

T a m o x i f e n / g o s e r e l i n


( 9 0 m i n / s e s s i o n ) ; 3 - h s i -


P H Y : c o r t i s o l , m e l a t o n i n , D

H E A S

C a r l s o n e t

a l .

2 0 0 5

6 3

5 4

B r e a s t , p r o s t a t e , o v a r -

i a n , N H L

M i x e d




( 9 0 m i n / s e s s i o n ) ; 3 - h s i -

l e n t r e t r e a t a t w e e k 6

P S Y : s l e e p ( P S

Q I ) , s t r e s s ( S O S I

m e n t a l h e a l t h c o m p o n e n t s ) , m o o d

a n d f a t i g u e ( P O

M S ) P H Y : S O S I

p h y s i c a l h e a l t h c o m p o n e n t s

G a r l a n d e t

a l .

2 0 0 7

6 0

5 2 . 1 7

B r e a s t , p r o s t a t e , c o l -

o r e c t a l , l u n g , e a r /

n o s e / t h r o a t ,

b r a i n ,

s k i n , l y m p h a t i c , o t h e r

N o t s p e c i -

f i e d



( 9 0 m i n / s e s s i o n ) ; 3 - h s i -


P S Y : p o s t - t r a u m a t i c g r o w t h ( P T G I -

R ) ; s p i r i t u a l i t y ( F A C I T - S p ) ; s t r e s s

( S O S I m e n t a l h e a l t h c o m p o n e n t s ) ,

m o o d ( P O M S ) P H Y : S O S I p h y s i c a l

h e a l t h c o m p o n e n t s

Mindfulness and cancer 573


DOI. 10.1002/pon



confidence intervals and the computation of a zscore calculated based on this mean and itsstandard error. Homogeneity testing was done todetermine if all the eff ect sizes estimated the samepopulation eff ect size, and a file-drawer testconducted where appropriate to determine pub-

lication bias. Four sets of mean eff ect sizes werethus determined: mental health and physical healthmean eff ect sizes for the randomized-controlledstudies and observational studies.

Results

We retrieved 15 original studies that involvedcancer populations, but only 10 reports, compris-ing 583 individuals who completed pre- and post-assessment, were included in the meta-analysis.

Studies that were found but not retrieved usedmindfulness meditation for non-cancer patientpopulations, while other studies involved non-patient populations. Among those retrieved, twowere excluded since they were follow-up studies[25,26], thus outside of the required time frame forthis meta-analysis. Another study reported inade-quate data for the immediate post-interventionfollow-up, providing more detailed data only forthe one-year follow-up [27]. Another study inves-tigated MBSR in a heterogeneous patient popula-tion, of which only 12% of the patient sample hadcancer and no subgroup data were reported [14].A fifth study was excluded since it did not utilizeMBSR therapy [28]. Of the remaining eligiblestudies, all were published, with four beingrandomized, controlled, and the other six beingobservational.

Generally, patients had a high level of education(an average of 15 years of formal education fromthe studies that provided such data), and a meanage of 54.75, except for the prostate cancer patientswho were generally older (mean age 67.4) (Table 1).

With 9 of the 10 eligible studies focusing onbreast cancer, majority of the patients who

participated were female, comprising 79% of thetotal cancer patient population meta-analyzed(Table 2). The modal stage of various types of cancer was Stage II, with patients either still inactive disease or in remission while participating inthe MBSR programs. Of the total pre-interventionpatient population from seven studies that reportedthe breakdown of cancer staging (two studiesoverlapped patients), 81% of participants were inearly stages (Stages 0–II), with the remaining 19%in late stages (Stages III–IV).

The mean drop-out rate for seven studies that

reported such data (two studies overlapped pa-tients) was 23%. The most frequently cited reasonsfor dropping out were scheduling conflicts, cancer-related treatment, and/or complications andhealth-related problems [29–31]. However, patients T

a b l e 1 .

( C o

n t i n u e d )

A u t h o r

Y e a r

N a

M e a n a g e

( y e a r s )

T y p e o f c a

n c e r

S t a t u s o f

c a n c e r

T r e a t m e n t s t a t u s

C o n c u r r e n t t r e a t m e n t

T y p e a n d d u r a t i o n o f

m i n d f u l n e s s t r a i n i n g

O u t c o m e m e a s u r e s

S a x e e t

a l .

2 0 0 1

1 0

6 7 . 4

P r o s t a t e

N i n e i n

r e m i s s i o n

P o s t - r a d i c a l p r o s t a t

e c t o m y


1 2 w e e k l y c l a s s e s o f

3 – 4 h e a c h ( b a s e d o n

U M - S R C p r o g r a m )

P H Y : r a t e o f P S A

i n c r e a s e a n d

d o u b l i n g t i m e

T a c o n e t

a l .

2 0 0 5

2 7

5 3 . 3

B r e a s t

M i x e d

I n a c t i v e t r e a t m e n t

T h r e e p a t i e n t s u n d e r g o i n g r a -

d i a t i o n o r c h e m o t h e r a p y , o r

s u r g e r y ; 2 4 p a t i e n t s t a k i n g o r a l

m e d i c a t i o n

8 - w e e k M B S R p r o g r a m -

U M ( o n c e a w e e k ,

9 0 m i n / s e s s i o n )

P S Y : m e n t a l a d j u

s t m e n t ( M A C ) a n d

h e a l t h l o c u s o f c o n t r o l ( M H L C )

R C T , r a n d o m i z e d , c o n t r o l l e d t r i a l s ; n o n - R C T , n o n - r a n d o m i z e d , c o n t r o l l e d t r i a l s ; N H L - n o n - H o d g k i n ’ s l y m p h o m a ; M B S R , m

i n d f u l n e s s - b a s e d s t r e s s r e d u c t i o n ; M B A T , m

i n d f u l n e

s s - b a s e d a r t t h e r a p y ; U M - S R C , U n i v e r s i t y o f M a s s a c h u s s e t t s S t r e s s R e d u c t i o n

C l i n i c ; P S Y , p s y c h

o l o g i c a l m e a s u r e s ; P H Y , p

h y s i c a l m e a s u r e s ; 7 D D R , 7

- d a y d i e t r e c a l l ; Q O L , q u a l i t y o f l i f e ; S C L - 9 0 - R , S y m p t o m s C h e c k l i s t R e v i s e d ; S F - 3 6 , M e d i c a l O u t c o m e s S t u

d y S h o r t - F o r m H e a l t h S u r v e y ; P O M S , P r o f i l e o f M o o d S t a t e s ; S O S I , S y m t p o m s

o f S t r e s s I n v e n t o

r y ; S C I , S h a p i r o C o n t r o l I n v e n t o r y ; S T A T E , S p e i l b e r g e r S t a t e A n x i e t y I n v e n t o r y ; B D I , B e c k D e p r e s s i o n

I n v e n t o r y ; S O C ,

S e n s e o f C o h e r e n c e ; P E N N ,

P e n n S t a t e W o r r y Q u e s t i o n n a i r e ; D H E A S , D e h y d r o e p i a n d r o s t e r o n e s u l f a t e ; P S Q I ,

P i t t s b u r g h S l e e p Q u a l i t y I n d e x ; P T G I - R , P o s t - T r a u m a t i c G r o w t h I n v e n t o r y - R e v i s e d , F

A C I T - S p , F u n c t i o n a l A s s e s s m e n t o f C

h r o n i c I l l n e s s T h e r a p y — S p i r i t u a l W e l l - B e i n g ; P S A , P

r o s t a t e - S p e c i f i c A n t i g e n ; M A C , M e n t a l A d j u s t m e n t t

o C a n c e r , M H L C , M e n t a l

H e a l t h L o c u s o f

C o n t r o l .

a P a t i e n t s w h o c o

m p l e t e d p o s t - a s s e s s m e n t .

b P a t i e n t s e i t h e r w i t h a c t i v e d i s e a s e o r i n r e m i s s i o n .

c S a m e s u b j e c t s u

s e d .



DOI. 10.1002/pon



with more advanced stages of cancer were not morelikely to drop out than those in the earlier stages,and participants in the control group were notmore likely to drop out than those in the treatmentgroup [32]. Some studies also reported that those

who dropped out had higher baseline POMS scoresin depression, anger, and confusion than those whocompleted the study [31,32].

Mental health variables

For the mental health variables of all controlledstudies, a moderate mean eff ect size d 5 0.37 (95%CI .10–0.64, po0.003, two-tailed) was calculated[33]. Calculation of the Q statistic showed homo-geneity of eff ect sizes (w25 5.12, df 5 2, p50.0773). These data represent a total of 224

individuals, with 116 receiving intervention (seeTable 3).For the mental health variables of all observa-

tional studies, we computed a moderate mean eff ectsize d 5 0.50 (95% CI .39–0.62, po0.0001, two-

tailed), representing data from 192 cancer patientsundergoing MBSR intervention. The Q test alsoshowed homogeneity (w25À19.23, df 53).

The overall mental health eff ect size (of bothcontrolled and observational studies) showed amoderate mean eff ect size d 5 0.48 (95% CI0.38À0.59, po0.0001, two-tailed). We also foundhomogeneity in the overall data (w25À13.34,df 5 6), thus we can assume that all the mentalhealth eff ect sizes estimate the same populationeff ect.

A file-drawer test to determine publication biaswas conducted [24], and showed that 10 unpub-lished studies with zero eff ect sizes were needed toreduce the mean eff ect size to 0.2 (upper limit of asmall eff ect size), and this was deemed unlikely.

Physical health variables

For physical health variables of all controlledstudies, we obtained a small mean eff ect size

d 5 0.17, which was not statistically significant(95% CI À0.07 to 0.40). Computation for the Qstatistic showed homogeneity of eff ect sizes(w25 2.43, df 5 2, p5 0.2963). These data representa total of 340 individuals, with 149 in theintervention group (Table 3).

For physical health variables of all observa-tional studies, a small mean eff ect size d 5 0.18(95% CI 0.07À0.29, po0.0009, two-tailed) wascalculated. Computing for the Q statistic showedthe data to be heterogeneous (w25 26.27, df 5 4),thus an adjusted mean eff ect size using a random

eff

ects model was determined, showing a value of d 5 0.19 which was, however, not statisticallysignificant (95% CI À0.01 to 0.38). The datarepresent 176 cancer patients who underwentMBSR intervention.

Table 2. Studies by type of cancer, proportion of patients by cancer stage (pre-intervention values), and drop-out rate

Type of cancer Stage of cancer Drop-outs

Author Breast Prostate Hematologic Gynecologic

Gastro-

intestinal Neurologic Other

Stages

0–II

Stages

III–IV

Drop-outs

(%)

Herbert et al. 172 172 9

Monti et al. 51 13 19 5 23 57 54 16

Shapiro et al. 63 63 35

Speca et al. 45 4 10 6 7 24 51 39 17

Carlson et al.a 33b 9b 59 29

Carlson et al.a 33b 9b 59 29

Carlson et al. 37 4 4 4 14 c c 0

Garland 34 3 5 2 16 c c c

Saxe et al. 10 7 2 0

Tacon et al. 27 c c 32.5

Totald 462 30 27 29 12 7 77 409 95

aSame subjects used.bOnly post-intervention data;cNo data.d

Carlson et al.’s subjects counted only once.

Table 3. Computed mean effect sizes for mental and physicalhealth measures

Type of study k N d 95% CI p

A. Mental health measures

RCT 3 224 0.37 0.10–0.64 o0.003

Observational 4 192 0.5 0.39–0.62 o0.0001

Overall 7 416 0.48 0.38–0.59 o0.0001

B. Physical health measures

RCT 3 340 0.17 –0.07–0.40 —

Observational 5 176 0.18 0.07–0.29 o0.0009

Overall 8 516 0.18 0.08–0.28 o0.0001

k, number of studies; N, number of patients; d , effect size; RCT, randomized,

controlled studies.



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Data from both randomized and observationalstudies showed an overall physical health meaneff ect size d 5 0.18 (95% CI 0.08À0.28, po0.0003,two-tailed). This mean eff ect size also failed thehomogeneity test (w25 28.72, df 5 7), and thereforemust also be interpreted with caution. Applying a

random eff ects model, the mean eff ect size wasd 5 0.18, which remained significant (95% CI0.03À0.33).

A file-drawer test to determine publication biaswas also conducted, and showed that 136 unpub-lished studies with zero eff ect size were needed toreduce the small eff ect size to one with no eff ect(0.01), and this was deemed unlikely.

Discussion

Many cancer patients are willing to undergodiff erent kinds of alternative therapies for variousreasons, such as stress reduction, to help boosttheir immune systems, to deepen their appreciationfor their religious upbringing, or to relieve somepsychic discomfort [34,35].

Our study revealed that recruited patients werepredominantly in the early stages of cancer (eitherin active treatment or in remission), were mostlywomen with breast cancer, and had an averagehigh level of education, giving us a general pictureof the kinds of cancer patients willing to try MBSRtherapy. That most of the patients were in earlystage cancer points to the idea that physical abilityto go to the study site and complete the interven-tion is an important factor and, in some studies,was an important inclusion criterion [36,37].

Our results show the efficacy of a mindfulnessmeditation-based psychosocial intervention forcancer patients in dealing with psychosocial stres-ses brought about by the disease (mental healthmean eff ect size d 5 0.35 for randomized studies,d 5 0.50 for observational studies). Specifically, itaids patients in relieving anxiety, stress, fatigue andgeneral mood and sleep disturbance, and helps in

improving the psychological aspects of their qualityof life.

Qualitative studies of the experiences of cancerpatients practicing mindfulness meditation havereported that mindfulness became a disciplinedapproach that helped patients improve the qualityof their lives and made them feel more open to newand novel experiences, less vulnerable to stress,more tolerant of negative aspects of self and others,and caused greater appreciation for life as ameaningful process [35,38]. At the same time,patients were less emotionally reactive and had

greater tolerance for strong emotions when theydid arise [35]. Since the core of mindfulnessmeditation is remaining in a non-judgmentalawareness of the present moment, this can readilybe understood as a consequence of continuous

practice. This may also be a strong contributingfactor to the improvement of depressive symptomsin cancer, as Spiegel and Giese-Davise [3] notedthat one factor that may moderate the relationshipbetween depression and cancer is the managementof the depressive feelings [3].

However, it is possible that patients’ attitudestoward the intervention itself may have been afactor for improvement in mental health. In therandomized studies, positive anticipation in terms of the patients randomized to treatment groups mayhave contributed to the success of the treatment forthem. Conversely, patients assigned to the controlgroup may have felt disappointment and may nothave improved as much spontaneously over time asthey would have otherwise [32].

Our data are consistent with Grossman et al .’s[18] meta-analysis, which reported mean eff ect sizes

of d 5

0.54 and 0.50 for mental health variablesfrom randomized and observational studies, re-spectively [18], and is also consistent with the post-intervention eff ect size of d 5 0.59 from mixedpopulations reported by Baer [11].

Meta-analysis of the physical health variablesshowed a small mean eff ect size in both controlled(d 50.17) and observational studies (d 5 0.18).These data are in contrast to Grossman et al .’s[18] study that found physical health mean eff ectsizes of d 5 0.53 (controlled studies) and d 5 0.42(observational studies) [18].

Our meta-analysis was severely limited by thesmall number of eligible studies available, leadingus to incorporate studies reporting on physiologicalparameters and those summarizing self-reportquestionnaires. Grossman et al .’s [18] study re-ported mean eff ect sizes only from self-reportquestionnaires [18], thus the disparity in our resultswould point to the mitigating eff ect on the overallmean eff ect size of physiological parameter studies,which generally reported no significance.

In fact, an analysis of the included studiesshowed that one of the three controlled studiesand two of the five observational studies noted no

or very little significant changes in physicalparameters (e.g. body mass, dietary fat, complexcarbohydrates, fiber, hormone and immune levels)[30,31,39], while the rest of the studies presentedimproved outcomes on self-report questionnaires(e.g. cardiopulmonary, gastrointestinal, or centralor neurologic symptoms) [29,32,40,41]. One studyon the other hand was distinct in that although itmeasured a physical parameter (prostate-specificantigen (PSA) levels and doubling time) it showeda large mean eff ect size. However, it contributedlittle to the overall eff ect size due to its small sample

size of 10 patients [36].With an increase in the number of studiesanalyzing the eff ects using either self-report ques-tionnaires or physiological parameters, it is possi-ble to separately meta-analyze results in order to



DOI. 10.1002/pon



improve homogeneity. Indeed, computing sepa-rately for the total physical health measures in thepresent analysis, the mean eff ect size of studiesreporting self-questionnaire results increased tod 5 0.26 (95% CI 0.13À0.38, po0.0001, two-tailed), bringing it closer to Grossman et al .’s [18]

results. On the other hand, using only physiologicalparameter studies for meta-analysis showed adecreased eff ect size d 5 0.06 (95% CI À0.08 to0.22). Still, with the promise shown by Saxe et al .’s[36] study on PSA levels, further studies usingphysiological parameters could improve ourknowledge in this area.

Because self-report questionnaires are filled outby the patients themselves, it is possible thatsubjective assessments still come into play whenassessing physical variables, where, if the patientfeels mentally relaxed because of the meditation, it

may influence the patient’s own assessment of hisor her physical symptoms in a positive way. Theyoga component of the intervention programscould have also contributed to patients’ morepositive assessment of their physical symptomspost-intervention, as highlighted by a pilot study of yoga for breast cancer survivors, which reportedincreased flexibility and a trend toward improve-ment in SOSI scales over time [42].

Determination of the physiological parametersafter only a short time post-intervention may alsohave been a factor in the resulting small mean eff ectsize, as also the fact that many of the patients werein the early stages of cancer, and were more or lessphysically functional in terms of their endocrine orimmune systems. Carlson et al . [30] cited in theirstudy that the patients had high levels of function-ing from the beginning, hence proposing that theMBSR program may be only moderately eff ectivefor early stage breast and prostate cancer patients[30].

Conversely, a few of the studies reportingphysical health measures also included patientswho were still in active treatment [29,39]. It is thuspossible that patients who were still undergoing

chemotherapy, radiotherapy, and other forms of cancer treatment would show very little improve-ment in the physical component assessments. Incontrast, patients who were in remission at the timeof enrollment in the study of Saxe et al . [36] showedconsiderable improvement in their physiologicaland physical symptom parameters [36].

In this meta-analysis, only four controlledstudies were found to be eligible, thus an additionalsix observational studies were included in order toincrease the number of analyzable data. Althoughmore studies could have been included, factors

such as methodological inconsistencies and inade-quate reporting of results limited the number of eligible studies.

Among the included studies, most had smallsample sizes and there was a lack of information

about the therapists (only a few studies explicitlyreported the utilization of MBSR program-trainedinstructors), patient compliance with at-homeexercises, and the cancer staging of patients post-intervention. The varying styles of implementationof this intervention may also have confounded the

results. Further, MBSR programs include not justmeditation per se, but also psycho-education andyoga, thus it is difficult to pinpoint which aspectcontributes most to the observed improvements inthe patients. It is also unclear as to how the patientsare deemed to have achieved a state of mindfulnessor have just achieved a simple state of mentalrelaxation. Intention-to-treat analyses were pro-vided by only one study [32], highlighting themethodological weakness of studies in this area.

Finally, our conclusions should be taken cau-tiously since our meta-analysis relied to a larger

extent on data from observational studies, and thusmay have been aff ected by the inherent methodo-logical weakness present in such studies.

Since Grossman et al .’s [18] meta-analysis of MBSR in patient populations, more studies, inparticular randomized, controlled types, involvingcancer patients have been conducted. This reflectsthe increasing clinical interest in MBSR in theoverall treatment of cancer patients, as well as thepossibility of improving methodological techniquesin assessing the eff ects of MBSR.

The small number of studies included in thismeta-analysis point to our inability to generalizethese results to the overall cancer population.However, the homogeneity of results found amongthe mental health variables allows us to concludethat MBSR is eff ective in improving the psychoso-cial conditions of breast cancer patients.

The inconsistency of the physical health mea-sures reflects the inadequate amount of informa-tion currently available on the efficacy of MBSR inthis aspect. However, exceptional results for PSAlevels show the promise of further research in thisarea. More methodologically sound researches onMBSR with larger sample sizes are needed to

validate the overall results.

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