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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
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
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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.
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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.
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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)
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49 2
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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.
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SOCIAL SUPPORT AN D PHYSIOLOGY
503
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504
UCH1NO, CACIOPPO,
AN D
K1ECOLT-GLASER
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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.
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UCHINO, CACIOPPO,
AND
KIECOLT-GLASER
c
y
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SOC IAL SUPPORT A N D PHYSIOLOGY
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SOCIAL SUPPORT
AND
PHYSIOLOGY
509
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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
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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
associations between social support
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 ) .
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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
associations between social support
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
associations between social support
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
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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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