apoyo social y enfermedad review.pdf

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Psychological

Bulletin

1996. Vol.

1 1 9 ,

No. 3,488-531

Copyright

1996bv theAmerican Psychological Association, Inc.

0033-2909/96/$3.00

TheRelationship Between Social SupportandPhysiological Processes:

AReview With EmphasisonUnderlying Mechanisms

and

Implications

for

Health

BertN.Uchino

University

ofU tah

JohnT.

Cacioppo

andJaniceK.Kiecolt-Glaser

Ohio S tateU niversity

Inthis

review,

theauthors examinetheevidence linking social support tophysiological processes

andcharacterizethepotential mechanisms responsiblefo rthese covariations. Areviewof

8 1

studies

revealedthat social support

w as

reliably related

tobeneficial

effects

on

aspects

of the

cardiovascular,

endocrine,

an d

immune systems.

A n

analysis

of

potential mechanisms underlying these associations

revealed that(a) potential health-related behaviorsdo notappearto beresponsibleforthese associ-

ations;

(b)

stress-buffering effects operate

in

some studies;

(c)

familial sources

of

support

may be

important;and( d )emotional support appearsto be atleast1important dimensionofsocial support.

Recommendations

an d

directions

fo r future

research include

t he

importance

of

conceptualizing

social supportas amultidimensional construct, examinationofpotential mechanismsacrosslevels

of

analyses,andattention to thephysiological processo finterest.

Social relationshipsare aubiquitous part oflife,serving impor-

tant social, psychological, andbehavioral functions across the life-

span. Moreimportant, both

the

quantity

and

quality

of

social

re-

lationships havebeen reliably related

to

morbidity

and

mortality

(see

reviewsbyBlazer,

1982;Broadheadetal., 1983;Cassell,

1976;

Cobb,

1976;S.Cohen&Syme, 1985;andHouse,

Landis,

& Um-

berson, 1988) .For

instance,

Houseet

al.

reviewed evidencefrom6

largeprospective studies indicating that mortalityishigher among

more socially isolated individuals. These associations hold even

afterinclusionofstandard control variables suchas age andinitial

healthstatus. Indeed, House

et al.

summarized evidence showing

that

theassociation

between social relationships

and

health

is

com-

parable with standard risk factors, including smoking, blood

pres-

sure,an dphysical activity.

An important issue concerns the potential mechanismsre-

sponsible

for the

epidemiological links between social relation-

ships

and

such long-term health consequences

(S .

Cohen,

1988;

S .Cohen &Wills, 1985;

Kiecolt-Glaser

&Glaser, 19 89) . In the

present review,

we first

examine

the

evidence linking

th e

posi-

Bert N .Uchino, Department of

Psychology

an d Health Psychology

Program, University

of

Utah; John

T.

Cacioppo, Department

of

Psy-

chology and

Brain, Behavior,

I mmu n i ty ,

an d

Health Program, Ohio

State University; Janice K. Kiecolt-Glaser, Department ofPsychiatry

an d

Brain,

Behavior, Immunity, an d

Health Program, Ohio State

University.

W e

thank Timothy Smith for hiscommentso n adraft ofthis article.

This study

w as

partially supported

by

Grants

T 3 2 - M H 1 8 8 3 1 ,

MH44660,

an d

MH42096

from th e

National Institute

of

Mental

Health,

asupplementto MH42 096from th eOffice ofWomen's Health,

Grant D B S 9 2 1 1 4 8 3 from th eNational Science Foundation, and the

John

D. and

Catherine

T .

MacArthur Foundation.

Correspondence concerning this article should

b e

addressed

to

Bert

N .Uchino, Department ofPsychology,5 02Social-Behavioral Sciences

Building,

U niversity

ofUtah, Salt Lake

City,

Utah 8 41 1 2 .Electronic

mail may be

sent

v ia

Internet

to

[email protected].

tiveaspectsofsocial relationships (i.e., social support)tophys-

iologicalprocesses.

We

characterize these associations

by

exam-

ining

the

influence

of social

support

on

aspects

ofthe cardiovas-

cular, endocrine, andimmune systems.The literature search

w asconducted using

the

ancestry approach

and

with

PsycLIT

(1974-1995) an d Medline (1983-1995) by crossing thekey-

words

socialsupport, social networks or social integrationwith

cardiovascular, blood

pressure endocrine

or

immune. Only

studies whose researchers directly examinedtheassociationbe-

tween

social support an dphysiological function were included

in

this review. Based onthis research, w eexamined potential

mechanisms responsible for the

associations

between social

support an dphysiologicalfunction (S .Cohen, 198 8 ) .

W esummarizetheresearch examining social supportandphys-

iological processes by using both qualitative and meta-analytic

procedures. Major details regarding studies (e.g., typeof support

assessment andmainfindings)werefirstcharacterized andana-

lyzed

in

tabular

form.

Based

on

this qualitative analysis, meta-

analytic procedures were used primarily when (a) thepattern of

results were equivocal

and (b)

there were

a

sufficient number

of

relativelyhomogeneous studies(e.g.,similar paradigms) toreli-

ablycharacterize

th e

effects

of

interest.

In

addition, meta-analytic

procedures were used

to

testspecifichypothesesfrom

ou r

qualita-

tive

analyses.

T he

meta-analysis

w as

performed using

a

commer-

cially available software package(Mullin, 1989)thatprovidedde-

tailed results regarding combined testsof

significance

levels,effect

sizes, tests

of

variability regarding significance levels

an d

effect

sizes, and a

fail-safe number.

1

Results of theunweighted meta-

analysis

a re reported, butanalyses weightedbysample size were

also performedand produced comparable results. Toreduce the

1

Th e fail-safe

number represents

the

number

of

unpublished

null

studiesthat would

be

needed

to

overturn

th e

conclusions

found in the

meta-analysis. Although there is no standard fail-safe number, Rosen-

thai ( 1 9 8 4 )suggests that

5k +

10,where

k

represents the number of

retrieved

studies, representsareasonable tolerance

level.

48 8


2/44

SOC IAL SUPPORT AND PHYSIOLOGY

489

problem

of

nonindependence

for

studies with multiple assess-

ments of social support, results were first transformed within a

studyto z scores, averaged, and then entered into themeta-analy-

sis. Therefore,

as

recommended

by

Rosenthal

(1984),

only

one

statistic

was

included fromeach study. Finally, when resultswere

reported

as

nonsignificant,

a

conservative significance

level

of .50

was

used

(Mullin,

1989).

Oneimportant sourceofheterogeneityin theliteratureon so-

cial support and health revolves around the conceptualization and

measurement ofsupport (Barrera, 1986;S .Cohen&Wills, 1985;

Heitzmann

&

Kaplan, 1988;Orth-Gomer&Unden, 1987;Tardy,

1985;

W inemiller,Mitchell,Sutliff,

&

Cline, 19 93).

In the

present

review,w e

include diverse studies with both structural (e.g., social

network)

andfunctional(e.g., emotional support) measuresofso-

cial

support.Structural measures of support assess the existence

and interconnection between various social relationships (e.g.,

number of

siblings), whereas functional measures

of

support

as-

sess

the

particular

functions

that social relationships

may

serve

(e.g.,providing emotional

or

informationalsupport).

The un-

derlying

theme

of

these assessments

is

that they conceptually mea-

sure the potentially positive aspects of social relationships. This

diversity

reflects,

inpart,the interestthatsocial support has gener-

ated in different

areas

ofinquiry(e.g.,sociology, psychology,and

health). Whenthenumbero fstudies permitted it, weperformed

focused

comparisons between structural

and

functional measures

of

support

to

examine

if

they

are

associated withquantitatively

different effects on

physiological

function (S .

Cohen

&

Wills,

1985).Inaddition, whenappropriatew ediscusstheimplications

ofboth measures

in

research regarding social support, physiologi-

cal

processes,and health.

Social Support and Physiological Processes

More than

18

years have passed sincetheseminal reviewsby

Cassell

( 1 9 7 6 )and

Cobb

( 1 9 7 6 )on the

importance

of

social

relationships

for

health.These

2

reviews

in

particular have been

responsible

for

generating interest

in

social support

and its

rela-

tionshipto psychological and physical well-being.Cobbfocused

primarily on the stress-buffering effects ofsocial support an d

emphasized the informational value of social support processes

(e.g.,thatone iscaredfor and loved)in fosteringcopingand

adaptation. Similarly, Cassell viewed social relationships

as po-

tentiallybuffering

th e

individual

from life

stressors

bu t

further

emphasized theimportanceofphysiologicalprocesses in medi-

atingtheeffectsofsocial relationships:

The

psychosocial processes thus

can be envisaged as

enhancingsus-

ceptibility todisease.T he

clinical

manifestations ofthis enhanced

susceptibility

will not be a function of the

particular psychosocial

stressor,

but of the physicochem ical or microbiologic

disease agents

harbored by the organism or to

which

the organism isexposed.

(Cassell,

1976,p.109)

As

suggested

by

Cassell,

the

associations between social support

and

physical health have been found

on

such diverse heath out-

comes (e.g., coronary heart disease, cancer, and infectious

illnesses)thatthere are probably multiple physiological path-

ways bywhich social support m ay

influence

diseasestates. In

thisreview,wefocuson thecardiovascular, endocrine, and im-

m u n e

systemsaspotential physiological pathwaysbywhichso-

cial

support

influences

physical health.

CorrelationalStudies Examiningth e

Asso ciation

Between

Social

Support and Cardiovascular

Function

O fthe

81studies whose researchers examined social support

and

physiological processes,

57

focused

on

aspects

of

cardiovas-

cular

function. This emphasis

is

understandable considering

thatcardiovasculardisorders

are

still

the

leading cause

of

death

inthe United

States

and that social support has been linked to

lowercoronary heart disease

(CHD)

rates (House etal.,1988).

Conceptually,

an

examination

of the

relationship between

so-

cialsupport and the cardiovascular system is important because

of its

implications

for

both

th e

development

and

maintenance

of

CHD. For instance, the prognostic value of tonic arterial blood

pressure in

predicting cardiovascular disorders

is

widely

ac-

cepted

(J. J.

Smith

& Kampine,

1990). Additionally,

the

reac-

tivityhypothesis suggests that increased cardiovascular reactiv-

ity

to

stress

may be an

important factor

in the

development

of

cardiovascular

disorders (see Krantz & Manuck,

1984;

Ma-

nuck, 1994;and Matthewsetal.,

1986).

Because

of the

relatively large number

of

studies examining

cardiovascular parameters,w e now

briefly

review basic princi-

plesofcardiovascular physiology.Thecardiovascular systemis

involvedin thetransportofoxygenand theremovalofcarbon

dioxide,

acritical

function

foreverycellandorganin thebody

(see

Larsen, Schneiderman,

&

Pasin, 1986;

and J. J.

Smith

&

Kampine, 1990,for

detailed

reviews).T he

heart muscle gener-

ates

the

necessaryforce

for the

circulatory process.

The

vascu-

lature (i.e., arteries, veins, and capillaries) serves as the vehicle

for thepumpingof theheart.

The

most commonly used cardiovascular measures

in

this

re-

viewinclude heart rate, systolic blood pressure

( S B P ) ,and

dia-

stolic

blood pressure (DBP). Heart rate, a measure of cardiac

chronotropy, is

usually

expressed in beats per minute. It is

jointly

determined

by the

sympathetic

and

parasympathetic

nervoussystems: Sympathetic activation increases heart rate,

whereas

parasympathetic activation decreases heartrate.

S BP and DBP are

measures

of the

force

of

blood against

the

arterial walls

and are a

function

of

both cardiac output

and the

relativestate

of the

vasculature. Because

of the

importance

of

blood pressure in the transport of blood, it is normally a regu-

lated endpoint.

SBP is

associated with ventricular contraction

(i.e., systole)and therefore corresponds to the peak arterial

pressure.

DBP is

associated with ventricular relaxation (i.e.,

diastole)

and corresponds to the lowest arterial pressure.

Fo rpurposes

of

this review,

it is

important

to

distinguish

be-

tweentonic

and

phasic components

of

cardiovascular activity

(Cacioppo, Berntson,&Andersen,

1 9 9 1 ) .

Tonic orbasal levels

of

cardiovascular activity provide information

on the

tonic

physiologicstate

of an

individual.

The

correlational studies

ex-

amining

the association between social support and cardiovas-

cular

function

have

focused primarily

on

tonic measures.

The

phasicor

reactivity components

o f

cardiovascular activity refer

to momentary fluctuations

from

tonic levels. Recent laboratory

studies, reviewed later, have

focusedon the

possibility that

so-

cial

support may reduce cardiovascular reactivity to acute psy-

chosocial stressors.


3/44

49 0

U C H I N O ,

CACIOPPO, A N DKIECOLT-GLASER

Animportant issue to consider is the psychometric properties

of

the physiological assessmentsbecause they bear on the po-

tential mechanisms linking social support to long-term physical

health. In this regard, it is conceptually important to distinguish

between measurement reliability

and

temporal stability.Mea-

surement

reliabilityrefers

to the

accurate assessment

of the

physiologicalstateat onepointin time. In comparison,tempo-

ra l

stabilityrefers to a

dispositional

characterization of physio-

logical function (i.e., stability

of the

physiological assessment

across different situations and occasions). Adequate measure-

ment reliability

is

necessary

but not

sufficient

for

temporal sta-

bility.

The distinction between measurement reliability and

temporal stability is important because if social support is to

have

effects

ondisease processes withalong-term etiology,the

physiological assessments should be characterized by temporal

stability. The assessment context (e.g.,specifictasks), popula-

tion (e.g., phobics), and techniques (e.g., specificityof tracers

inradioimmunoassay) may all influence anindividual differ-

ence assessment

of

physiological function.

As an

example,

a

needle stick

isoftenassociated

with relatively short-term eleva-

tionsincatecholamines. Becauseof themeasurement reliability

of

current techniques

( B a u m

&Grunberg,1 9 9 5 ),th ecatechol-

amine changes due to venipuncture would be accurately as-

sessed at that point in time. However, this may be a poor index

of

an individual's cathecholamine response across time and

situations.

Past researchers haveexaminedthetemporal stabilityofheart

rate, SBP,andDBF reactivity.A sreviewedby

Manuck,

Kaspro-

wicz,

Monroe,

Larkin,

and Kaplan

( 1 9 8 9 ) ,

measures of heart rate

reactivity evidence the strongest

test-retest

correlation, typically

rangingfrom.67 to

.91.

S BPreactivity tendstoevidence adequate

temporal stability that isslightly lower thanth estability seenfor

heart rate, whereas

DBF

tends to

show

relatively low

test-retest

stability. Although manyof thestudies reviewedbyManucket

al .

did not reportdataon the

test-retest

stability of tonic measures,

the patterns of stabilityacrossheart rate, SBP, and

DBF

appear

similartothat forreactivity assessments. Itshouldbenoted, how-

ever,that researchershavedemonstrated thatthestabilityofthese

cardiovascular assessments, including

DBF,

are enhanced consid-

erably when assessments

are

aggregated across multiple time

pointsandmultipletasks (Kamarck, 1992;KamarcketaL,1992;

Manuck, 1994).

There are several methodological issues related to an exami-

nation of the relationship between social support and cardio-

vascular function.

In

particular,

the use of

appropriate statisti-

cal

controls

is

important

as

many

of the

studies reviewed

in

this

section are correlational studies in which potential associations

withconfounding variables

may

occur.

For

instance, social sup-

port may be correlated with socioeconomic status,medication

use, age,

and

other factors that

mayhave

direct influences

on

physiological function. We should note that there is some dis-

crepancy

in the

literature

on

whether such variables

are

poten-

tial confounding variables or mechanisms by which social sup-

port has an association with health (S. Cohen,

1988;

House et

al.,

1988).

In our

tabular analyses

of

each study,

we

explicitly

note when such statistical controls were used.

In

addition,

we

discuss

the

attention

(or

lack thereof) paid

to

appropriate sta-

tistical controls

and its

implications

for the

mechanisms

un-

derlyingthe relationships between social support and cardiovas-

cular function.

Many of the studies on social support and cardiovascular

function

have used a correlational design with normotensive in-

dividuals.Table 1summarizes28correlational studies, most

ofwhich used middle-aged and older adult samples

from

the

community.Twentystudies examined both

men and

women,

5

examined only men,2examined only women, and 1study did

not report the gender composition of the sample. Researchers

of 14 of

these studies explicitly assessed some aspect

of familial

support. In addition, researchers of 7 studies assessed structural

measures

of

support,

of

15studies assessed functional measures

ofsupport,

and of 6

studies assessed both structural

and func-

tional measures of support.

In general, the results of the correlational studies are consis-

tent with the notion that higher social support isassociatedwith

better cardiovascular regulation (e.g., lower blood pressure). In

1

of the first

studies investigating

the

relationship between social

support

and

cardiovascularfunction,Kasl

and

Cobb(1980)

ex-

amined the

influence

of social support on blood pressure

changes

in response to job termination; they reported that per-

ceptions of social support were negatively related to blood pres-

surechanges

in

response

to job

loss.

To

summarize Table

1 ,

researchers of 23 studies reported some evidence that social

supportwasassociated with better cardiovascular function,of

4 studies reported no relationship (see Ely &Mostardi,

1986;

Houben, Diedriks, Kant,

&

Notermans, 1990; Kaufmann

&

Beehr,1986;

an d

Lercher, Hortnagl,

&

Kofler,

19 93), and of 1

reported opposite

effects

(Hansell,

1985) . Ameta-analysis of

21 correlational studies whose researchers reported data

on the

association between social support and blood pressure revealed

a significantcombined test( z =4.22,p =.00001,fail-safe n =

117.38) .

2

Th e

mean effect size

(r) w as

.08, suggesting

a

small

but

reliable

effect

across studies. None

of the

tests

ofvariability

w as

significant (p >.45).Thus,theevidencefor anassociation

between

social support and lower blood pressure levels appears

reliable.

W e

coded eachof thestudies includedin themeta-analysisas

measuringstructuralorfunctional measuresofsupport.Of the

6studies that assessed both types of support, we were able to

separate the

effects

in 4 ofthese studies. Therefore, data from 9

studies were identifiedasstructural, an ddata from 14studies

2

The meta-analysisconsistedof

21

studies that directly examinedthe

association between social support an dtonic blood pressure levels.In 2

cases,w e

averaged

the

results reported across

2

differentpublished stud-

ies(i.e., Dressier, 1980, 1983;Janes, 1990; Janes &Pawson, 1986)b e-

cause data were apparently reported on the same sample. In addition,

the 5studies examining job-related social support were excluded

from

thisanalysis because it had been identified a priori as a

feature

associ-

atedwithinconsistent

effects. In the

text,

w e

examine

in

detail potential

reasons

w hyjob-related

support

m ay be

associatedw ith weak

effects on

blood

pressure.

In o urinitial search,w eexcluded2studies examiningtherelationship

between

social support and blood pressure for methodological reasons

(James,

LaCroix, Kleinbaum,

&

Strogatz, 1984;

Orth-Gomer, Rosen-

gren, &Wilhelmsen, 1993). More specifically,these studies included

participantso ncardiovascular medicationbut did notaccount fo rthis

factor in reporting the association between social support and blood

pressure.


4/44

SOCIAL

SUPPORTAN DPHYSIOLOGY

491

were

identified

as

functional measures

of

support. Focused

comparisons

betweenthestructuralandfunctional

measures

of

support

revealed

n o

differences

in significance level(p =

.29)

or

effectsize(p =

.47).

Although appropriate caution

is

warranted

because of the

small

numberof

studies contrasted,

these

data

are consistent with the larger literature, suggesting that both

structural

and

functional measures

ofsupport

predict

benefi-

cial effects on

physical health. However,

the

specificpsychologi-

cal

and behavioral mechanisms that contribute to these

effects

may

differ

for structural and functional

measures(S.Cohen,

1988).We

return

to a

discussion

of

such issues later

in the

review.

Researchers in 3 of the 4

studies that

did not find anyrela-

tionship between indices

of

social support

and

blood pressure

regulation measuredjob-relatedsocial support (Houben

et

al.,

1990;

Kaufmann &

Beehr, 1986; Lercher

et

al.,1993). How-

ever, Winnubst, Marcelissen, & Kleber (1982) and Unden,

Orth-Gomer,&Elofssen(1991)also examined work-related

social support and reported some effects oncardiovascular

function.

One

potential

reason for this discrepancy may be re-

latedto thepsychometric propertiesof themeasuresof social

support.For example, the Lercher et al. measure of social sup-

port was two dichotomous questions (alsosee Houben etal.,

1990,

which also contains two questions), whereas Winnubst et

al.'s measure containedfivequestionsandUndenetal.'smea-

sure

containedsixquestions. AlthoughKaufmann andBeehr

did

report highinternal consistenciesfortheir job-related social

support measures(.59 90 mm/Hg, or

current

use of hypertensive

medication), particularly

in low

income Black

participants. These dataareconsistentwiththenotion thatspecific

support components may be moreeffectivewhen they meet the

demands of related situations.

One concern in these correlational studies was the rarity in

whichpsychometricdataregarding the measurement ofsocial

support werereported. Only 11studies made referenceto the

psychometric

properties

oftheir scale

(e.g.,

factor analysisand

internal consistency).Giventheheterogeneityinwhichstudies

summarized

in

Table

1 have

conceptualized

and

measured

so-

cial support, thescales'

psychometric

properties are important

to examine, especially for the less validated measures of

support.

Relatedly, onlyresearchersof 4studies inTable 1reported

any

data

on the

temporal stability

of the

cardiovascular assess-

t xt continues

on

page 499)


5/44

49 2

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CACIOPPO,

AND KIECOLT-GLASER

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50 2

UCHINO, CACIOPPO, AND KIECOLT-GLASER

leisure activities and, more important, lower SBP andDBF.The

control condition evidenced

no

such changes.

Only

researchers

of 2 of the

studies conducted

to

date

re-

portedno

effect

of a socialsupportintervention on blood pres-

sure

regulation (Arnetz, Theorell, Levi, Kallner,

&

Eneroth,

1983;

Gill,

Veigl,

Shuster,

&

Notelovitz,

198 4 ) .

However, Gill

et

al.

did not find a

significant manipulation check

on

social sup-

port, which suggests that

the

intervention

was

unsuccessful

in

affecting

participants' supportnetworks.

The

null

finding by

Arnetz et al. is

more difficult

to

explain. However,

familial

rela-

tionshipsmay berelatively important forblood pressure regu-

lation (seePo tentialMechanisms).

In

general, stronger associa-

tions might

be

obtained with interventions that focus

on

famil-

ial

sources of support.

Although

the

studies summarized

in

Tables

1 and 2

suggest that

social support influences cardiovascular function,

few of

these

studies suggested

its

effect

on

established risk factors.

To

this point,

wesummarize

8

prospective

(primarily intervention)

studies with

hypertensivepatients inTable3.Researchersof 5 of the 8studies

in

Table

3

explicitly noted that they examined both White

and

Black

participants. Researchers

of 6

studies examined both

men

and women, whereasof 2studies examined only men.S ix of the

interventions usedfor themost part familialsourcesofsupport.

However,

researchers

of 1

study simply assessed naturalistic social

support,

and of 1

study used organizational social support.

Evidence for the role of social support on cardiovascular

function

and

risk factors comes from

the

prospective interven-

tionstudiesonhypertensive individuals summarizedinTable

3. In an early study, Levine et al.

(1979)

identified 400 hyper-

tensive

patients and assigned them to interventions consisting

ofan

exit interview,

family

support, small group, various com-

binations of these groups (e.g., exit interview and family

support), or a control condition. In the

family

support condi-

tion, patients were asked

to

identify

a

target individual with

whom

they

had

frequent contact (typically

a spouse). The

target individuals were then trained to increase understanding,

support, and reinforcement regarding positive management of

thepatient's

hypertensive

state.

Results revealed that family

support alone decreased DBF (i.e., DBF was below the hyper-

tensive

limitsfor theparticipant'sparticularag e

group)

by 11%

at an 18-monthfollow-up assessment. Predictably, exposure to

all

intervention conditions was associated

with

the best blood

pressure control ( 2 8 % ) .Subsequent follow-upsofthis project

sample revealed reliable long-term effectsof the social support

manipulation on blood pressure regulation(M orisky,DeMuth,

Field-Pass,Green,

&

Levine, 1985; Morisky

et

al., 1983).

A

meta-analysis

of

studies whose researchers have used social sup-

portmanipulations

to

control blood pressure

in

at-risk popula-

tions (Earp, Ory,

&

Strogatz, 1982;

Erfurt ,

Foote,

&

Heirich,

1991;

Levine

etal.,

1979; Morisky

et

al., 1983, 1985; Stahl,

Kelley,

Neill,

Grim &Mamlin, 198 4 ) revealed a significant

combined test(z =3.32,p =.0004, fail-safe n =

12 .29) .

3

The

mean effect size

w asr = .15, and no

test

of

variability

w as

sig-

nificant

(p >.20).These prospective data fromat-risk popula-

tions provide evidence that social support

may

have beneficial

effects

on

established risk factors.

Although

the results of the prospective intervention studies

withnormotensives and hypertensives suggestthatsocial sup-

port leads to better blood pressure regulation, there are several

issues raised by these studies. The prospective intervention

studies with hypertensives were primarily designedtoaffecttan-

gible aspects of support. However, the social support manipula-

tions may have

affected

other

aspects

of social support, includ-

ing

appraisal support

due to the

increased

participationand

knowledge

of the

support

provider. Furthermore, although

these studies suggest tangible support may have been important

because

of

better medical adherence (e.g., Levine

et

al.,1979),

none of the studies researchers performed statistical analyses to

directly examine

the

importance

of

thisfactor.Interestingly,

the

prospective intervention studies generally preceded

the

correla-

tional studies summarizedinTable 1that suggest tangible fac-

tors alone cannot explain

the

associations between social sup-

port

and

blood pressure regulation. Therefore,

the

prospective

data are only suggestive of tangible support influences on blood

pressure regulation because other unmeasured components of

social support

may

have contributed

to

these

effects.

W eshould also note that aspects

of

several interventionswith

normotensive participants might have affected other health-

related processes (e.g., Andersson, 1985; Sallis, Trevorrow,

Johnson, Hovell, & Kaplan,

198 7 ) .

For instance, the Sallis et al.

manipulation also informed participants

of the

h a rm f u l effects

of

stress

(alsosee

Clifford, Tan,

&Gorsuch, 1 9 9 1 ) .

Therefore,

lifestyle

or

behavioral changes related

to

stress,

but not

directly

involving

socialsupport,may have also contributed to the re-

sults

of these studies. Nevertheless, the prospective design of the

studies

in

Tables

2 and 3,

along with

the

importance

of

blood

pressure regulation in hypertensive individuals, provides rela-

tivelystrongevidence linking

social support

torisk factors.

PotentialMechanisms Linking SocialSupport to

Cardiovascular Function

Because of the consistency of the associations between social

support

and

cardiovascular parameters presented

in

Tables

1 to

3,

we now

turn

to specifyingthe

potential mechanisms respon-

sibleforthese covariations.In areviewofpotential mechanisms

linking

social support to health, S. Cohen

(1988)

suggests that

social support m ayhave beneficialeffectsthrough social (e.g.,

stress

buffering),

psychological (e.g.,

affectivestates),and be-

havioral(e.g., health-promoting) mechanisms. Consistent with

S .Cohen( 1 9 8 8 ) ,

we

examined

the

mechanisms linking social

support

to

physiological processes

at

differentlevels

of

analysis

(also

see

Cacioppo

&

Berntson,

1992).

Atasocial psychologicallevelofanalysis,itappears thatfa-

milial sources of social support may be associated with reliable

effects

on

blood pressure regulation.

A

meta-analysis

of

12

cor-

relational studies whose researchers explicitly noted that they

3

The meta-analysis consisted of 4 studies that used social support

manipulations

tocontrol blood pressureinat-risk populations.Onetest

statistic is entered forthe 3 Levine et al. and Morisky et al. studies above

to

reduce potential problems with

the

nonindependent samples.

The

Pinto, Sirota,

and

Brown ( 1 9 8 5 )study

was not

included because

no

statistics were presented for their case study. For all prospective studies,

the

statistic entered

was the

difference

in

blood pressure level

or

control

betweenthe social support manipulation and a control condition during

the finalassessment, thereby providing evidenceon thelong-term effects

ofthese interventions.


16/44

SOCIAL SUPPORT AN D PHYSIOLOGY

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18/44

SOCIAL SUPPORT

AND PHYSIOLOGY

505

assessed social support related

to family

members revealed

a

reliable

combined test

ofsignificance (z =

4.17,p =.00001,

fail-safe n=64.97).T he

associatedeffect size

for

this analysis

wa sr .12,

and no

test

of

variability

w as

significant(p >.09).

In

1

study w hose researchers directly exa m ined blood pressu re

in

the

presence

of

different

social relationships,

Spitzer, Llabre,

Ironson, G ellman,

an d

Schneiderman( 1 9 9 2 )found that being

around afamily member wasassociatedwith lower am bulatory

SBP and DBF compared with being around a friend or a

stranger. The prospective interventions with hypertensive pa-

tients that directly used

family

members

as

sources

of

support

provide convergent evidence on the importance of familial

sources of support on blood pressure regulation.

Researchers

of 8 of the

correlational studies have directly

tested the potential

stress-buffering

effects of social support on

cardiovascularfunction (Dressier, 1980,

1991;

Dressier, M atar,

etal., 1986; Janes, 1990; Kasl & Cobb, 1980;

Kaufmann

&

Beehr, 1986; Strogatz

&

James, 1986;W innubst

et

al.,

1982).

As

argued by S. Cohen and W ills {1 98 5), one methodological

requirementfor atestof the

buffering

model consistsofdemon-

strating

a

significant main

effect for thestress

assessm ent

to en-

sure that the measure was characterized by an adequate range

of

scores

an d

m easurem ent reliability. However, only research-

ers of 4 of these studies reported data indicating that their m ea-

sure ofstresswasassociated withblood p ressure. These4stud-

ieswere

associated

withasignificant

combinedtest (

z=3.39,p

=.0003,

fail

safen

=

12.99)and aneffect sizeofr = . 18. Notest

of

variabilityw as significant (p > .34). In 1illustrative study,

Dressier

(1980 ) reported

an interaction between structural

measures

of

suppo rt (i.e.,

no. of

siblings)

and

levels

of

lifestress

for

SBP and

DBF: Individuals high

in

number

of

siblings

and

low in life

stress

werecharacterized by the lowestblood pres-

sure. Although Cohen

and

Wills suggest that

buffering

effects

are

more likely

to be

found when there

is a

reasonable match

between the

stressor

typeandsupport function, theyalsore-

ported that

buffering effects

were sometimes

found

when

re-

searchers assessed close interpersonal relationships. Consistent

with Cohen and W ills, all5studies whoseresearchersexamined

familial

relationships (e.g., spouse and siblings) reported asig-

nificant

buffering effect

oncardiovascular regulation (z = 3.43,

p

=

.0003,

fail-safe n =16.74), with

an

effect size

ofr =

.14.

N o

testofvariability wassignificant

(p >.55)*

These studies fur -

therunderscorethepotential importance ofexaminingfamilial

sources

of

social suppo rt

in

studies

of

cardiovascular regulation.

Th e studies summarized in Table 2 suggest that structured

interactions with others m ayalso produce

beneficial

effects on

cardiovascular func tion. However, these resultsm ay notsimply

be a functionof theintervention discussion because such struc-

tured interactions appear to generalizeto othersinone's net-

work

(e.g.,A ndersson,1985). Therefore,

the

studies

in

Table

2

m ay producepart of their effects by increasing social compe-

tence

or theperceived im portanceofsocial interactionsin one's

social network (Sallis etal., 1987).

At

am ore behavioral

level

o fanalysis, partof the association

between

social support

and

cardiovascular function

may be a

result of health-related lifestyle factors

(Umberson,

1987). For

example,social support may be associated with better cardio-

vascular regulation because ind ividu als high in social support

engage

in better health practices (e.g., better diet and more

physical activity). C ontrarytothisposition,theassociationsbe-

tweenaspectso fsocial supportand cardiovascular

function

re-

mained significant even afterstatistically controlling for

a

num-

ber ofhealth-related variables, includ ing weightor body mass

(e.g., Blandet

al.,

1991 ; Janes &Pawson, 1 986; Stavig,Igra, &

Leonard,

1984).

How ever,

it

should

be

noted

that

many

of

these

researchers havenot

assessed

specific health-related behaviors

(e.g., substance abuse). In addition, of those researchers that

did assess specific health-related behaviors, data on the reliabil-

ity or valid ity of their assessments we re typically notreported

(see

Umberson, 1987).

Atapsychological levelofanalysis, perceptions ofstress, feel-

ings

ofcontrollability, intrusiveorrum inative thinking, feelings

of loneliness, depression, and other emotional processes (e.g.,

anxiety)are potential psychological mechanisms for theassoci-

ations between social support

and

cardiovascular function

(Collins, Dunkel-Schetter, Lobel, & Scrimshaw, 1993;Pierce,

Sarason,

&

Sarason, 1991; Quittner, Glueckauf,

&

Jackson,

1990;

Russell &Cu trona, 1991;Stokes, 1985; Solomon, Miku-

lincer,

&Hobfoll, 19 86).

U nfortunately,

empirical data are un-

available

concerningthepsychological mechanisms responsible

for the

associations

between

social

support and cardiovascular

function reported in Tables 1-3. Future research is clearly

needed in this area ofinquiry.W e return to this imp ortant point

later in the review.

LaboratoryStudiesExamining th eEffects ofSocial

Support

on

Cardiovascular Function

Whereas

the

prior studies have focused primarily

on

tonic

measures of cardiac function, many of the recent studies have

been experimental, laboratory

studies

conducted underthe ru-

bricof thereactivity hypothesis. Briefly, thereactivity hypothe-

sis

suggests that exaggerated cardiovascular reactivityto stres-

sorsm ay be a pathogenic mechanism influencingthe develop-

ment

of cardiovascular disorders (see Krantz & Manuck,

1984;

Manuck,

1994;

and

Matthews

et al.,

1986). These

15

studies

aresummarized inTable4.Thirteenofthese studies tested rel-

ativelyyoungparticipants und er

the age of 30. O ne

study used

a middle-aged sample, and 1 study used an older adultsample.

Researchers of 8 of these

studies

exclusively exam ined wom en,

of3 examined m en, and of 4 examined both m en and women.

In 1 1 studies, researchers examined social support throughex-

perimental manipulation. Researchers

of the

remaining

4

stud-

iesassessed

n atura listic levels of socialsupport.Of these 4 stud-

ies, 3

studies' researchers exam ined fun ctional measures

of

sup-

port, and 1

examined

a

combined index

of

structural

an d

functional

support.

The

laboratory studies

in

Table

4

collectively suggestthat

so-

cial supp ort m ay reduce cardiovascular

( or

autonomic nervous

system)reactivity

to

acute psychologicalstress.

O ne

salient fea-

(textcontinuesonpage 510)

4

W e should note th at 4 of the 5 studies' researchers wh o assessed

familialsources

ofsupport

also

reported

significant

effectsoftheir stress

measures. Therefore, the influenceof

close

interpersonal relationships

and the methodological requirement suggested by S. Cohen and Wills

(1985) are

potentially

confounded

in

these meta-analyses

of

buffering

effects.


19/44

506

UCHINO, CACIOPPO,

AND

KIECOLT-GLASER

c

y


20/44

SOC IAL SUPPORT A N D PHYSIOLOGY

507

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22/44

SOCIAL SUPPORT

AND

PHYSIOLOGY

509

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1

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.49)

.*

6

A

literature search

onPsycLIT(

1974- 1994)

a ndMedline(1983-

1994)

crossing

the

keywords

immuneo r

immunology withpsychomet-

ricsorreliabilityrevealed no additional researchers who had exam ined

the

temporal stability

of the

im m un e assessments discussed

in

this

review.

7

O ur

initial search produced

2 4

studies whose researchers exam ined

the

relationship between social support

and

i m m u n e

function. W e ex-

cluded analyses of 6 studies in part or in w hole for several reasons. Data

on

the relationship between social support and

white

blood cell or total

lymphocyte

counts

were

not included in the present

review

(Arnetz et

al.,

1983;

R. S.

Baron, Cutrona,

Hicklin,

Russell,

&

Lubaroff,

1990;

Mclntosh, Kaplan, Kubena, & Landmann, 1993; Thomas, Goodwin,

& Goodwin, 1985) because

of

difficulties

in

interpreting

the

signifi-

cance

of

these m easures.

In

addition,

w e

excluded

1

study that exam -

ined salivary

IgA

(Jemm ott

&

Magloire, 1 98 8) because

of

m ethodolog-

ical issues regarding the reliability of the salivary IgA assessment that

was

used

in

this study (Herbert

&

Cohen, 1993a; Stone, Cox,

Valdimarsdottir, &Neale, 1987) .O nestudywasalso excludedfrom the

review

because

the

small number

of

participants

(3 ) in

their

lo w

stress

and no social support

cell

precluded

definitive

an alyses (Herrera, Alva-

rado, & M artinez, 1988 ).

8

The meta-analysis consisted of 9 studies whose researchers directly

examined the association between social support and functional mea-

sures

of

i m m u n e

function. To

reduce problems

associated

w ith nonin-

dependence, the results of

Snyder,

Roghmann, and

Sigal

(1990, 1993)

were

averaged

to

produce

one

test statistic because data were reported

from

the

same sample.

S ix

studies were excludedfrom

the

m eta-analysis

because it was determined a priori that intervention studies and popu-

lations

w ith individuals

having HI V

w ere associated w ith inconsistent

effects.These studies are discussed in detail later in the text.

In

the meta-analysis, we examinedfunctional imm une measures be-

cause there were

only4

rem ainin g studies whose researchers examined

the association between social support and quan titative measures of im-

m u n e function.

The interested reader is referred to Table 5 for a sum -

mary of the

relationship between social support

an d

quantitative

im -

m u n e

measures.

In

addition, there

were

only

2

remaining studies that


33/44

52 0

UCHINO, CA CIOPPO,

A N D

KIECOLT-GLASER

Tw o of the studies that did not find an association between

social support and immunological data were interventions de-

signed to facilitate social interactions (Arnetzetal., 198 7; Kie-

colt-Glaseretal.,1985). The Kiecolt-Glaser et al.(19 85)inter-

vention documented increased social contact and interactions.

However, keep

in

m ind that

the

sam ple sizes

in 2 of

these stud ies

are relatively small

(n

< 45.00). In addition, we reviewed evi-

dence earlier suggestingthat familial sources of support may

be important. It is possible that interventions aimed directly at

increasing

familial

contact and support may yield even larger

effects sizesonimm une function.

Tw o

of the studies

that

did not find a

significant

association

between social support and aspects of imm une fu nction exam-

ined men who

wereHIV+ (Goodkin

et

al., 199 2; Perry, Fish-

m an, Jacobsberg, & Frances, 1992) .There are important m eth-

odological reasons that might explain a lackof an association

between social support and immune function in individuals

H IV + . For instance, stage of disease, age, gender, dru g abuse,

and health behaviors are potentially important confounding

variables (Ironson et al., 1994).

However, 2 recent studies have reported an association be-

tween social support and CD4+ counts (a marker of HIV

progression) in men with HIV (Persson, Gullberg, Hanson,

Moestrup,&O stergren, 19 94; Theorelletal., 19 95). In 1pro-

spective study with

data

across a 5-year period, Theorell et al.

found

that

th eavailability ofsociala nd emotional support pre-

dicted subsequent changes inCD4+counts in a representative

Swedish sample

of men

with HIV. Results revealed that high

and low social support groups did not differ in CD4+ counts

duringthe early years of the study. How ever, the prediction of

CD4+ counts as a

function

of social support w as evident du ring

Years

4 and 5 of the study. For instance, during Year 5 of the

study,individu als highinsocial su pport showeda 3 7 % change

in CD4+ counts, whereas individuals

low in

social support

showeda -64% changeinCD4+counts (Theorellet

al.,

1995) .

Note that Perry et al.

( 1 9 9 2 )

reported nullfindings on the rela-

tionship between social support and CD4+ counts only up to

Year 1 of their study. These preliminary prospective data sug-

gest that social support may

influence

the progression of HIV

infection

and

provide evidence

on the

utility

of

su ch long-term

prospective designs.

An

important implication

of

these data

is

that if a researcher was to only examine the relationship be-

tween

social support and C D4+ counts later in the stage of dis-

ease, information on the longer length of time that individuals

highin social support took to get tothatstage wou ld be lost.

9

A

population of particular interest in this review is older

adults because social support may be especially important for

these individuals (House etal., 1988) . Alterations in im m une

function m ayhave significant consequences in this population

as

aging

is

associated w ith

a

dow n regulation

o f

i m m u n efunc-

tion

(Goidl, 19 87; Goodw in, Searles,&Tung, 19 82; Roberts-

Thomson, W hittingham, Youngchaiyud, &

Mackay,

1974;

Schleifer,Keller, Bond, Cohen, &Stein, 1 9 8 9 ) , andinfectious

illnesses

are the

fourth leading cause

of

death

in the

elderly

included

a

structural assessment

of

support. Therefore, focused com-

parisons

between structural

an d

functional measures

of

support were

not performed.

(Effros &

Walford,

1987) .

Excluding

th e

intervention studies

discussed earlier,it isimportant tonotethatthe association be-

tween social support and functional measures of immunity is

consistent

in

older adults.

A

meta-analysis

of 7studiesin

mid-

dle-agedtoolder adult populationsconfirmed this hypothesis (z

=

4.27,

p =.000009, fail-safe n=

40.30), with

a neffect

size

of

r= .23.Notestof

variabilityw as

significant (p> .35) .

Although

9 studies' researchers examined both men and

women, 8 studies' researchersdid not report analyses aimedat

examining

potential genderdifferences. In the only study with

data on potential gender differences, Thomas, Goodwin, and

Goodwin

( 1 9 8 5 )foundthat

the availability of a confidan t was

associated with

a

stronger proliferative response

to PHA for

women but not men.

How ever,

th e

correlations were

in the

same

direction, and no statistical test was performed to directlytest

the difference between men and wom en. In addition, Thomas et

al. provided a conservative test of the effects of social support

on im m un efunction,

as

they statistically controlled

for

psycho-

logical distress as

well

as potential health-related variables (e.g.,

alcohol consumption).

Sim ilar conceptual issues exist in the research exa m ining so-

cial

support

and

im m une function

as in the

research reviewed

earlier.O n ly2 of thestudies summarized inTable5conceptu-

alized social support as a m ultidimensional construct and re-

ported analyses regarding a relatively specific dimension of so-

cial

support

(R. S.

Baron

et al.,

1990; Persson

etal.,

1994).

Although

3

additional studies used multidimensional social

support m easures, results wereonly reported on the total scale

(e.g., Glaser, Kiecolt-Glaser, Bonneau, Malarkey, & Hughes,

1992;

G oodkin

etal., 1992; Perry

etal.,

19 92). An examination

of relatively distinct dimensions of social support may have

revealed

greater specificity (Glaser et al., 19 92) and stronger


an d

i m m u n e function

(Goodkin

et

al., 199 2; Perry

et

al., 1 9 9 2 )

due to a

better m atch

between

thesample needsand thesupport resource.

PotentialMechan isms Linking S ocialSupport to

Immune Function

The studies summarized in Table 5 suggest that social sup-

port

is associated with better immune function. These results

and

a

recent meta-analysis conducted

by

Herbert

and

Cohen

( 1 9 9 3 a ) provide converging evidence for the effects of social

support on physiological

function.

However, Herbert and Co-

hen

only exam ined aspects

of

im m une function

and

focused

on

social stressorsinvolving

the

loss

or

disruption

of

interpersonal

resources (e.g., bereavement and marital conflict).

As in the review of social su pport and cardiovascular fun ction

(see Tables 1-3 ), the studies sum m arized in Table 5 suggest

that close relationships, such as fam ilial ties, m ay be a particu-

larlyim portant source of social support. Researchers of 2 stud-

ies

assessed social support specific to close relationships

(Levy

9

Weshouldnote that atypical strategy in such designs mightbe to

statistically

control for the length of

time

since illness. However, if the

interaction between thiscovariatean dsocialsupportwere significant,it

would invalidatethe use ofthis

statistical

control procedure(J. Cohen

&

Cohen, 19 83)

bu t

accurately reflect

the findings of

Theorell

et al.

( 1 9 9 5 ) .


34/44

SOC IAL SUPPORT AND PHYSIOLOGY

52 1

etal., 1990; Thomas et

al.,

1985), and both found social sup-

port

to be

related

to

aspects

of

immune function, including

a

stronger proliferativeresponse to PHA and greater NK cell lysis.

Researchersof 4 of thestudiesinTable5directlytested the

bufferingmodel of social support (Goodkin etal., 1992;

Kie-

colt-Glaser,

Dura,

Speicher,

Trask,

&

Glaser,

1 9 9 1 ;

Snyder,

Roghmann,

&

Sigal, 1990, 1993).

Of

these studies, onlyKie-

colt-Glaseret al. ( 1 9 9 1 )reported a reliable effect of stress on

immune

function.Asnoted earlier,S.CohenandW ills( 1 9 8 5 )

argued that this is a methodological requirement for an ade-

quate test

of

the

buffering

model. More important,

Kiecolt-Gla-

ser et al. found

evidence

for a

buffering

effect of

social support

on

immunefunction.However, becauseof thesmall numberof

studies, moredataare needed to adequately test the buffering

model on immune function.

Tw oof thestudies summarizedinTable5conceptualizedso-

cial

support

as a

multidimensional construct

and

reported anal-

yses regarding relatively

specific

dimension

of

social support

(R. S. Baron etal.,1990; Levy et al., 1990). Levy et al. exam-

inedthedimensionofemotional

support

from

aspouse (orin-

timate other) and emotional support

from

one's doctor and

foundboth to beassociatedwith greater NK celllysisin cancer

patients. In a study of spouses of cancer patients, Baron et al.

used the social provisions scale and foundthat higher levels on

all

support

dimensions(i.e.,guidance, reliable alliances, reas-

surances of worth, social integration, attachment, and opportu-

nity fornurturance) were equallya nd significantly associated

witha stronger proliferative response to PHA and greater NK

cell lysis. A snoted byBaron et al., caring for a spouse with

cancermay result in a mobilization ofone'ssupport network,

suchthatthere was little

differentiation

among support compo-

nents. Consistent with this possibility, Baron et al. reported high

intercorrelations among the components of support.

Levy

et al. (1990)

suggest that emotional support

may be one

dimension

of

social support that

is

associated with immune

function.Researchers of 4 additional studies also assessed, in

part,emotionalsupport(also see R. S. Baron et al., 1 9 9 0 ).Kie-

colt-Glaseret al.

( 1 9 9 1 )

and Esterling, Kiecolt-Glaser, Bodnar,

andGlaser ( 1 9 9 4 )used acompositeindex of emotional and

tangible support. Snyder

et al.

(1990, 1 9 9 3 )used

a

composite

index of

emotional

and

informational support.

A

meta-analysis

ofthese studies revealedasignificant combined testof signifi-

cance

(z =

4.02,p

=

.00003,fail-safen

=

24.90).

The

effectsize

associatedwith this test wasr =.26, and no test of variability

w as significant (p > .44).Thesedata suggestthatemotional

supportmay be atleastone important aspect of social support

in

predicting immune function. Additional research

is

needed,

however,

that directly compares the predictive utility of specific

dimensions of socialsupport.

At

a

behavioral level

of

analysis, part

of the

association

be-

tweensocialsupport

and

immunefunction

may be due to

their

effects onpotential health-related variables

(Kiecolt-Glaser

&

Glaser, 1988b). Several researchers assessed the effectsof po-

tential health-related behaviors andfoundthat the associations

between social support and immune function were significant

evenwhen statistically controllingforhealth practices (Thomas

etal.,1985; also see Theorell, Orth-Gomer, & Eneroth, 1990).

Thesedataareconsistentwith results reviewed earlier on social

supportand blood pressure, suggesting that such behaviors do

not appear to be necessary for an association between social

support

and

immune

function.

However, these

findings

should

be

taken

as

preliminary, given

the

restricted number

of

health-

related

practicesassessed

and the

lack

of reported

data

on the

validityand reliabilityofsuch assessments in manyofthese

studies.

Psychological

factors such

as

levels

of

stress

and

depression

havereliableeffects

on

immune function (Herbert

&

Cohen,

1993a,

1993b). Therefore, part of the association between so-

cial

support

and

immunefunction

may be

mediated

by

these

factors.Researchers of 3 studies in Table 5 reporteddatarelat-

ing

to

potential psychological mechanisms responsible

for the


and

immune function

(R. S.

Baron

et

al., 1990; Glaser

etal.,

1992; Kiecolt-Glaser

et

al., 1 9 9 1 ) .Baron et al.(1990) foundthat the associations be-

tween

social support and immune functionwere not mediated

by lifeevents.Inaddition, Baronet al.(1990)an dKiecolt-Gla-

ser et al. (1 9 9 1 )

foundthat depression

was not

mediating

the

associations between social support and immunity. Finally, Gla-

ser

et al.

( 1 9 9 2 )

reported

evidence indicating that anxiety levels

were

not

responsible

for the


and

immunefunction.Therefore, although health-related

be-

haviors, depression, and life stress have reliable effects on as-

pects of immunefunction, these factors do not appearto be

majorpathways

explainingthe

associations between social sup-

port and immunefunction.

Discussion

Social support has been linked to lower rates of morbidity

and

mortality

from

diverse disease processes and endpoints.

Therefore,

the

majoraims

of

this review were

to

examine

the

evidencelinkingsocial support

to

multiple aspects

of

physio-

logical

function

and tocharacterizethepotential mechanisms

responsibleforthese covariations.To thebestof ourknowledge,

this

is the first

comprehensivereview

on

this topic.

The

present

review

indicates that there

is

relatively strong evidence linking

social support to aspects of the cardiovascular, endocrine, and

immunesystems. These

dataare

consistent with research sug-

gestingthattheformationanddisruptionofsocial relationships

haveimportant immunological

and

endocrinological sequalae

in n o n h umanprimatesand humans(Coe, 1993;Gunnar,1992;

Herbert & Cohen, 1993a). More important, the physiological

systems

reviewedmay

playimportant roles

in the

leading causes

of

death

in the

United States, including cardiovascular disor-

ders, cancer, and respiratory illnesses.

10

Conceptual and meth-

10

C. E.

Smith, Fernengel, Holcroft, Gerald,

an d

Marien

(1994)

con-

ducted

a

m eta-analysis

on the

effects

of

social support

on

various health

measures,

including

physicalandstress-related outcomes. They opera-

tionalized

stress outcomesasreportsof negative lifeevents,conflict or

distress, andlaboratory measures,suchascatecholamine levels. Physi-

calhealth status

w as

operationalized

assubjective

states, such

as

symp-

t om s

a nd

signs,

and as

objectivedata, such

as

weightloss, activities

of

daily

living,

blood pressure, blood glucose,andreportsof sexualactivity

posthysterectomy.

Th eresultsof the

meta-analyses

revealed

effect size

estimatesranging

from

.01 to.22.S m ithet al.concluded thatth erela-

tively smalleffect sizessuggest thattherelationship between social sup-

port an d healthm ay not be

significant

orgeneralizable.

Thereare

several issues that warrant discussion regarding

the C. E.

S m ithet al.( 1 9 9 4 )meta-analysis.First, Smithet al. did notpresentany


35/44

522

UCHINO,

CACIOPPO,

AND

KIECOLT-GLASER

odologicalissues were also raised regarding the associations be-

tweensocial support and physiological processes. We now turn

tothese issues.

One basic andrecurring issuein thesocial support

literature

relatesto the measurement of socialsupport(Barrera, 1986; S.

Cohen

&

Wills, 1985; Heitzmann

&

Kaplan, 1988;

Orth-

Gomer&Unden, 1987;

Tardy, 1985; Winemiller

etal.,

1993).

Questions remainaboutthe factorstructure of social support

and the temporal stability and psychometric properties of such

assessments.

In the

present review,

few

studies' researchers

re-

porteddata pertainingto thepsychometric propertiesoftheir

socialsupportmeasures. Given the heterogeneity in the mea-

sures of socialsupportcovered in this

review,

psychometricdata

m ayhelpclarifyreliable relationships.

An additional measurement issue concerns the specific

sources of socialsupport.The present reviewindicates that fa-

milialtiesappearto be an important source of social support

to consider in studies of physiological function.Socialsupport

researchers might gain greaterspecificity

and

prediction

by ex-

amining specific types of

social

relationships. The studies sum-

marized in this

review

whose researchers examined cross-cul-

tural

andgender

effects

ofsocial supportareexamplesofsuch

applications. In addition, behavioral data obtained during lab-

oratory studiesmay amplify the relationships found between

self-report data and physiological processes (e.g., Kiecolt-

Glaser et al., 1993; Malarkey,Kiecolt-Glaser,Pearl, & Glaser,

1994 ) .

Most of the studies reviewed in this article

have

conceptual-

ized

social support as a unidimensional construct. As noted ear-

lier,multidimensional assessments m ayallowfor anexamina-

tion

of

more specific associations

and

mechanisms

(Uchino,

Cacioppo,Malarkey, Glaser, & Kiecolt-Glaser, 1995).For in-

stance, Seeman et al.( 1 9 9 4 )foundthat emotional support was

a more consistent predictor of neuroendocrine

function

than

informational

support.More important, such

specificity

would

have

been lost

if an

aggregate measure

of

social support

was

used.

The

relative importance

of

specific dimensions

of

social

data

on

combined tests

of

significance

for the

relationships that they

examined.Therefore,someof therelationships between social support

m ay havebeen statisticallysignificant,albeit characterized

by

small

to

moderate

effect

sizes. Second,

th e

aggregation

of

suchdiversemeasures

asindicesofphysical healthandstress outcomes(seeabove)may ob-

scurereliable relationships

within

particular measures (e.g., blood pres-

sure and

catecholamines). Finally,

and

perhaps most important,

the

selection

o f

studies

in the

meta-analysis

w as

limited. None

of the

major

prospective studies

on

social relationship

and

mortality were included

in themeta-analysis (see Housee tal., 1988,for areview).Inaddition,

thereappearsto belittle overlapin thestudies examinedinSmithet al.

and the

present

review. Th e

reasons

for

this discrepancy

is

unclear

be -

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