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COMMENTARY
Psychological Stress and Disease
Sheldon Cohen, PhD
Denise Janicki-Deverts, PhD
Gregory E. Miller, PhD
DESPITE WIDESPREAD PUBLIC BELIEF THAT PSYCHO-
logical stress leads to disease, the biomedical com-
munity remains skeptical of this conclusion. In
this Commentary, we discuss the plausibility of
the belief that stress contributes to a variety of disease pro-
cesses and summarize the role of stress in 4 major diseases:
clinical depression, cardiovascular disease (CVD), human
immunodeficiency virus (HIV)/AIDS, and cancer.
What Is Psychological Stress?
Psychological stress occurs when an individual perceives that
environmental demands tax or exceed his or her adaptive
capacity.1Operationally, studies of psychological stress fo-
cus either on the occurrence of environmental events that
are consensually judged as taxing one’s ability to cope or
on individual responses to events that are indicative of this
overload, such as perceived stress and event-elicited nega-
tive affect. In this article, the definition of stress excludes
psychiatric disorders that may arise as downstream conse-
quences of stressful exposures and also excludes disposi-
tions often linked to stress, such as hostility and type A
behavior.
Pathways Linking Psychological Stress
to Disease
Generally, stressful events are thought to influence the patho-
genesis of physical disease by causing negative affective states
(eg, feelings of anxiety and depression), which in turn ex-
ert direct effects on biological processes or behavioral pat-
terns that influence disease risk.1Exposures to chronic stress
are considered the most toxic because they are most likely
to result in long-term or permanent changes in the emo-
tional, physiological, and behavioral responses that influ-
ence susceptibility to and course of disease.1,2 This in-
cludes stressful events that persist over an extended duration
(eg, caring for a spouse with dementia) or brief focal events
that continue to be experienced as overwhelming long af-
ter they have ended (eg, experiencing a sexual assault).3
Behavioral changes occurring as adaptations or coping re-
sponses to stressors such as increased smoking, decreased ex-
ercise and sleep, and poorer adherence to medical regimens
provide an important pathway through which stressors in-
fluence disease risk. Stressor-elicited endocrine response pro-
vides another key pathway. Two endocrine response sys-
tems are particularly reactive to psychological stress: the
hypothalamic-pituitary-adrenocortical axis (HPA) and the
sympathetic-adrenal-medullary (SAM) system. Cortisol, the
primary effector of HPA activation in humans, regulates a
broad range of physiological processes, including anti-
inflammatory responses; metabolism of carbohydrates, fats,
and proteins; and gluconeogenesis. Similarly, catechol-
amines, which are released in response to SAM activation, work
in concert with the autonomic nervous system to exert regu-
latory effects on the cardiovascular, pulmonary, hepatic, skel-
etal muscle, and immune systems. Prolonged or repeated ac-
tivation of the HPA and SAM systems can interfere with their
control of other physiological systems, resulting in in-
creased risk for physical and psychiatric disorders.1,2
That HPA and SAM systems mediate the effects of stress
on disease is supported by experimental evidence from ani-
mal as well as human studies that show a wide variety of
stressful stimuli provoke activation of these systems. How-
ever, stress also may influence disease risk through its ef-
fects on other systems. For example, psychological stress
has been found to impair vagal tone,4which also can in-
crease disease risk, particularly for CVD.
Effects of stress on the regulation of immune and inflam-
matory processes have the potential to influence depres-
sion; infectious, autoimmune, and coronary artery disease;
and at least some (eg, virally mediated) cancers.5Psycho-
logical stress might alter immune function through direct
innervation of lymphatic tissue, through release of HPA and
SAM hormones that bind to and alter the functions of im-
munologically active cells, or through stress-induced be-
havioral changes such as increased smoking.
Healthy human individuals exposed to acute laboratory
stressors show an adaptive enhancement of some markers
of natural immunity but a general suppression of functions
of specific immunity.6By comparison, exposure to real-life
Author Affiliations: Department of Psychology, Carnegie Mellon University, Pitts-
burgh, Pennsylvania (Drs Cohen and Janicki-Deverts); and Department of Psy-
chology, University of British Columbia, Vancouver, British Columbia, Canada (Dr
Miller).
Corresponding Author: Sheldon Cohen, PhD, Department of Psychology, Car-
negie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213 (scohen@cmu
.edu).
©2007 American Medical Association. All rights reserved. (Reprinted) JAMA, October 10, 2007—Vol 298, No. 14 1685
at University of Pittsburgh, on January 4, 2008 www.jama.comDownloaded from
chronic stress (eg, unemployment, caregiving for the chroni-
cally ill) is associated with a biphasic immune response in
that partial suppression of cellular and humoral function
coincides with low-grade, nonspecific inflammation.6
Although stressors are often associated with illness, the
majority of individuals confronted with traumatic events and
chronic serious problems remain disease-free.3There has
been considerable interest in identifying individual differ-
ences in vulnerability to potential pathogenic effects of stress
with emphasis on genetic as well as psychological factors.
Does Stress Cause Disease?
The fundamental question—Does stress cause disease?—
can only be evaluated rigorously by experimental studies.
Ethical considerations prohibit conducting experimental hu-
man studies of the effects of stress on the pathogenesis of
serious disease. However, there is evidence from “natural
experiments” that capitalize on real-life stressors occur-
ring outside of a person’s control such as natural disasters,
economic downsizing, or bereavement. There also have been
attempts to reduce progression and recurrence of disease
by psychosocial interventions. However, clinical trials in this
area tend to be small, methodologically weak, and not spe-
cifically focused on determining whether stress reduction
accounts for intervention-induced reduction in risk. In con-
trast, evidence from prospective cohort studies and natural
experiments is informative. These studies typically control
for potentially confounding demographic and environmen-
tal factors such as age, sex, race/ethnicity, and socioeco-
nomic status.
Stress and Depression. Stressful life events have been
linked to major depressive disorder as well as to depressive
symptoms.7-9 During the 3 to 6 months preceding the onset
of depression, 50% to 80% of depressed persons experi-
ence a major life event, compared with only 20% to 30% of
nondepressed persons evaluated during the same period.9
Approximately 20% to 25% of persons who experience ma-
jor stressful events develop depression.10
Although most investigations have focused on life events
as triggers of depression onset, increased stress also pre-
dicts the clinical course of major depression, including fea-
tures such as longer duration, symptom exacerbation, and
relapse.7,8 Evidence also suggests that events that occur con-
currently with treatment reduce positive response.8
Stress and Cardiovascular Disease. Experimental work
with animals provides strong support for a stress-elicited
increase in coronary artery disease, with indication that the
effects of stress are mediated by protracted SAM activa-
tion.11 Laboratory experiments in healthy adults and car-
diac patients indicate that stress can foster pathogenic pro-
cesses such as myocardial ischemia and activate inflammatory
and coagulatory mechanisms.12
Prospective research conducted among initially healthy
human populations provides considerable support for a link
between psychological stress and CVD morbidity and mor-
tality.11,12 One meta-analysis estimated an approximate 50%
increase in CVD risk associated with high levels of work
stress, defined as low workplace control coupled with high
demands, inadequate compensation, or organizational
injustice.13
Long-term CVD risk is also increased among initially healthy
individuals who experience traumatic events, such as the death
of a child, or who are exposed to emotional, sexual, or physi-
cal abuse during early life.14,15 Similar patterns are found in
natural experiments examining the rates of cardiovascular
events following natural disasters and war.11,12 Recurrent CVD
events and mortality among persons with preexisting CVD
are similarly increased with perceived life stress, job over-
load, marital distress, and social isolation.11
Stress and HIV/AIDS. Individuals differ with regard to
rate of progression through the successive phases of HIV
infection. Some remain asymptomatic for extended peri-
ods and respond well to medical treatment, whereas others
progress rapidly to AIDS onset and develop numerous com-
plications and opportunistic infections. Stress may ac-
count for some of this variability in HIV progression.
Evidence published before 2000 regarding the influence
of stress on HIV progression was largely inconsistent. How-
ever, that published since 2000 has generally supported a
link between stress and HIV progression.16(pp165-194) Some
evidence suggests that an accumulation of negative life
events over several years of follow-up predicts worse AIDS-
related outcomes. For example, among HIV-positive men,
each additional moderately severe event increased the risk
of progressing to AIDS by 50% and of developing an AIDS-
related clinical condition by 2.5-fold.17 Moreover, stress
has been found to influence the course of virally initiated
illnesses to which persons with HIV are especially suscep-
tible.18 These studies are supported by experimental re-
search with animals wherein exposure to social stressors
results in decreased survival.19
Better measures of stress may account for the positive find-
ings in later studies. These studies used objective ratings of
the stressfulness of events and focused on specific events
with highly personal consequences, such as bereavement and
stigma regarding sexual orientation. Another explanation
for positive findings in later studies is that the effects of stress
are due to poor adherence to highly active antiretroviral
therapy. However, stress may remain a risk factor even when
adherence is controlled, directly influencing HIV replica-
tion via increases in autonomic nervous system activity.20
Stress and Cancer. Experimental research in animals has
found that stress contributes to the initiation, growth, and
metastasis of select tumors. Moreover, mechanistic experi-
ments in humans indicate that stress affects key patho-
genic processes in cancer, such as antiviral defenses, DNA
repair, and cellular aging.21 Despite these promising find-
ings, evidence from prospective studies linking stress and
cancer incidence in humans is mixed at best.22-24 The lack
of consistent results may be because many cancers are di-
COMMENTARY
1686 JAMA, October 10, 2007—Vol 298, No. 14 (Reprinted) ©2007 American Medical Association. All rights reserved.
at University of Pittsburgh, on January 4, 2008 www.jama.comDownloaded from
agnosed only after they have been growing for many years,
making an association between stress and disease onset dif-
ficult to demonstrate.
It is generally believed that stress is more likely to influ-
ence the progression and recurrence of cancer than initial on-
set of the disease. Yet the critical prospective studies in this
area have been largely unsupportive. The lack of convincing
data on psychological stress as a risk for cancer onset, pro-
gression, or recurrence may be at least partly attributable to
the practical difficulties in designing and implementing ad-
equate studies. For example, studies frequently collapse groups
of patients across various types of cancer to maximize power.
Cancer is a heterogeneous group of diseases with multiple
etiologies, and the contribution of stress-related perturba-
tions (eg, HPA and SAM activation, diminished antiviral de-
fenses) likely varies across sites and stages. Of the more nar-
rowly focused studies, much emphasis has been placed on
breast cancer. However, stress effects are likely to be more
pronounced in other cancers, especially those facilitated by
impairments in antiviral immunity and sustained activation
of hormonal response (eg, cervical cancer, hepatocarci-
noma, and HIV-related tumors). Research in cancer progres-
sion also is limited by poor sensitivity to detect (and hence
control for) premorbid states and the inability to accurately
quantify severity at any disease stage.
Conclusions
Associations between psychological stress and disease have
been established, particularly for depression, CVD, and HIV/
AIDS. Other areas in which evidence for the role of stress is
beginning to emerge include upper respiratory tract infec-
tions, asthma, herpes viral infections, autoimmune dis-
eases, and wound healing.16
Evidence derived from prospective observational stud-
ies provides support for stress as an important factor in cer-
tain diseases but cannot establish a causal relationship. How-
ever, the results of these studies are consistent with those
of natural experiments regarding the effects of real-life
stressor exposure on disease risk; with those of laboratory
experiments showing that stress modifies disease-relevant
biological processes in humans; and with those of animal
studies investigating stress as a causative factor in disease
onset and progression. This consistency of research find-
ings strongly supports the hypothesis of a causal link. The
development of interventions that can reduce the behav-
ioral and biological sequelae of psychological stress and the
demonstrated efficacy of such interventions in random-
ized clinical trials would provide critical data on the clini-
cal importance of this work.
Financial Disclosures: Dr Cohen reported consulting for Johnson & Johnson Con-
sumer Companies Inc on issues of stress measurement. None of the other authors
reported any financial disclosures.
Role of the Sponsor: This article is based on a paper commissioned by the Insti-
tute of Medicine Committee on Psychosocial Services to Cancer Patients and Fami-
lies in Community Settings. The Institute of Medicine suggested the topic but played
no role in structuring the paper; in the collection, management, and interpreta-
tion of the data; or the preparation, review, or approval of the manuscript.
Additional Contributions: We thank David Krantz, PhD (Uniformed Services Uni-
versity of the Health Sciences), Margaret Kemeny, PhD (School of Medicine, Uni-
versity of California at San Francisco), Stephen Manuck, PhD, and Karen Mat-
thews, PhD (University of Pittsburgh), and Scott Monroe, PhD (Notre Dame
University), for their comments on an earlier draft; the John D. and Catherine T.
MacArthur Foundation Network on Socioeconomic Status and Health and mem-
bers of the Pittsburgh Mind-Body Center (HL65111, HL65112) for their intellec-
tual support; and Ellen Conser, MA, Ashleigh Molz, and Wesley Barnhart, BS (Car-
negie Mellon University), for assistance in preparing the manuscript. None of these
individuals received any extra compensation for their contributions.
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COMMENTARY
©2007 American Medical Association. All rights reserved. (Reprinted) JAMA, October 10, 2007—Vol 298, No. 14 1687
at University of Pittsburgh, on January 4, 2008 www.jama.comDownloaded from
