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DOI: 10.1111/j.1467-9280.2007.01867.x

2007 18: 165Psychological Science Alia J. Crum and Ellen J. Langer

Mind-Set Matters : Exercise and the Placebo Effect

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Research Article

Mind-Set Matters Exercise and the Placebo Effect Alia J. Crum and Ellen J. Langer

Harvard University

ABSTRACT—In a study testing whether the relationship

between exercise and health is moderated by one’s mind-

set, 84 female room attendants working in seven different

hotels were measured on physiological health variables

affected by exercise. Those in the informed condition

were told that the work they do (cleaning hotel rooms) is

good exercise and satisfies the Surgeon General’s recom-

mendations for an active lifestyle. Examples of how their

work was exercise were provided. Subjects in the control

group were not given this information. Although actual

behavior did not change, 4 weeks after the intervention,

the informed group perceived themselves to be getting

significantly more exercise than before. As a result, com-

pared with the control group, they showed a decrease in

weight, blood pressure, body fat, waist-to-hip ratio, and

body mass index. These results support the hypothesis that

exercise affects health in part or in whole via the placebo

effect.

The placebo effect is any effect that is not attributed to an actual

pharmaceutical drug or remedy, but rather is attributed to the

individual’s mind-set (mindless beliefs and expectations). The

therapeutic benefit of the placebo effect is so widely accepted

that accounting for it has become a standard in clinical drug

trials to distinguish pharmaceutical effects from the placebo

effect and the placebo effect from other possible confounding

factors, including spontaneous remission and the natural history

of the condition (Benson & McCallie, 1979; Brody, 1980; Nes-

bitt Shanor, 1999; Spiro, 1986). Kirsh and Sapirstein (1998), in a

meta-analysis of 2,318 clinical drug trials for antidepressant

medication, found that a quarter (25.16%) of the patients’ re-

sponses were due to the actual drug effect, another quarter

(23.87%) were due to the natural history of depression, and half

(50.97%) were due to the placebo effect.

The placebo effect extends much further than medications or

therapy: Subjects exposed to fake poison ivy developed real

rashes 1 (Blakeslee, 1998), people imbibing placebo caffeine

experienced increased motor performance and heart rate (and

other effects congruent with the subjects’ beliefs and not with the

pharmacological effects of caffeine; Kirsch & Sapirstein, 1998),

and patients given anesthesia and a fake knee operation ex-

perienced reduced pain and swelling in their ‘‘healed’’ tendons

and ligaments (Blakeslee, 1998). More generally, studies sug-

gest that 60 to 90% of drugs and other therapies prescribed by

physicians depend on the placebo effect for their effectiveness

(Benson & Freedman, 1996; Nesbitt Shanor, 1999).

The placebo effect does not have to involve inert pills or

sham procedures. Symbols, beliefs, and expectations can elicit

powerful physiological occurrences, both positive and negative

(Hahn & Kleinman, 1983; Roberts, Kewman, & Mercie, 1993).

For example, the mere presence of a doctor increases patients’

blood pressure (the ‘‘white coat effect’’), reinterpreting pain in

nonthreatening ways (e.g., as sensations) prompts patients to

take fewer sedatives and leave the hospital sooner; and the

health decline of cancer patients often has less to do with the

actual course of the illness and more to do with their negative

expectations regarding the disease (Langer, 1989).

EXERCISE AND THE PLACEBO EFFECT

As the most common health threats are now infectious rather

than chronic, remedies have also changed. Doctors now pre-

scribe behavioral changes such as exercise for chronic diseases

like diabetes, heart disease, and even cancer. We wondered

whether the well-known benefits of exercise are in whole or in

part the result of the placebo effect. A positive finding would

speak to the potentially powerful psychological control people

have over their health.

There is evidence supporting the idea that the placebo effect

plays a role in occasioning the psychological benefits associated

with exercise (Desharnais, Jobin, Cote, Levesque, & Godin,Address correspondence to Alia Crum or Ellen Langer, Department of Psychology, Harvard University, 1330 William James Hall, 33 Kirkland St., Cambridge, MA 02138, e-mail: [email protected] or [email protected].

1 When negative expectations are met with negative results, the placebo effect

is often called the nocebo effect (Hahn, 1997).

PSYCHOLOGICAL SCIENCE

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1993; Plante, Lantis, & Checa, 1998; Plante & Rodin, 1990).

Desharnais et al. conducted an experiment on 48 healthy young

adults engaged in a supervised 10-week exercise program. Half

of the subjects (the experimental condition) were led to believe

that the program was specifically designed to improve psycho-

logical well-being. The other half were not told anything about

these benefits; instead, the emphasis was on the biological as-

pect of the program. Although the results showed similar in-

creases in fitness in the two conditions, the subjects in the

experimental condition showed a significant increase in self-

esteem.

Although studies have yet to investigate whether the per-

ception of physical activity and resulting beliefs about one’s

health have effects on the physiological benefits associated with

physical activity, several studies allude to the possibility. Health

perceptions have been related to actual health. For example,

Kaplan and Camacho (1983), in a cohort study of 6,928 adults,

found that perceived health was a better predictor of mortality

than actual health. Idler and Kasl (1991) concluded that elderly

persons who perceive their health as poor are 6 times more likely

to die than those who perceive their health as excellent, re-

gardless of actual health status.

Further support for the possibility of the placebo effect in the

benefits of exercise comes from the fact that the numerous

studies linking exercise to health have generally relied on self-

reported information to measure physical activity (Plante &

Rodin, 1990); the results of these studies therefore reflect the

relationship between health and perceived levels of physical

activity, rather than actual levels. This raises the question of

whether some of the positive gains of physical activity are due

more to the perception of exercise and its association with health

than to the actual performance of exercise.

In the study we report here, we investigated the role of the

placebo effect (the moderating role of mind-set) in the rela-

tionship between exercise and health. We hypothesized that the

placebo effect plays a role in the health benefits of exercise: that

one’s mind-set mediates the connection between exercise and

one’s health. If this hypothesis is true, increasing perceived

exercise, independent of actual exercise, would be expected to

result in subsequent health benefits (a placebo effect).

METHOD

Logic

The Surgeon General has stated that all adults should accu-

mulate at least 30 min of physical exercise per day for a healthy

lifestyle (Centers for Disease Control and Prevention, CDC,

1996). Everyday moderate physical activity can be achieved by

taking a brisk walk, climbing the stairs, or performing active

housework (CDC, 1996). Although many people today have

sedentary jobs, there are some jobs that are intrinsically phys-

ical. Hotel room attendants, for example, clean on average 15

rooms a day (each room taking between 20 and 30 min to

complete), and engage in exerting activities that require walk-

ing, bending, pushing, lifting, and carrying, clearly meeting and

exceeding the Surgeon General’s requirements. Room attend-

ants may not perceive their work as exercise. If they do not, and

if the relationship between exercise and health is moderated by

mind-set as we hypothesize, then these workers may not be re-

ceiving the full health benefits of their exercise. Similarly, if

their mind-sets are shifted so that they become aware of the

exercise they are getting, then health improvements would be

expected to follow.

Design

Each of seven hotels was randomly assigned to one of two con-

ditions: informed or control.

Subjects in the informed condition received a write-up dis-

cussing the benefits of exercise and were informed that their

daily housekeeping work satisfied the CDC’s recommendations

for an active lifestyle. Specifically, they were told that exercise

does not need to be hard or painful to be good for one’s health,

but that it is simply a matter of moving one’s muscles and

burning calories (accumulating approximately 200 calories per

day to meet the recommendations). They were given specific

details of the average calorie expenditure for various activities

(changing linens for 15 min burns 40 calories, vacuuming for 15

min burns 50 calories, and cleaning bathrooms for 15 min burns

60 calories), and they were told that although these figures were

based on results for a 140-pound woman and each of them would

burn calories at a different rate, it was clear that they were easily

meeting and even exceeding the Surgeon General’s recom-

mendations. 2 This sheet, written in both English and Spanish,

was read and explained to the subjects and then posted on the

bulletin board in their lounge. 3

The subjects were told we were interested in getting infor-

mation on their health so that we could study ways to improve it,

and in return for helping, they would receive information about

research on health and happiness.

Subjects in the control group were given all the same infor-

mation as those in the informed group except they did not re-

ceive information about how their work is good exercise until

after the second set of measures was taken (see Procedure).

Subjects

Subjects were recruited through hotels. To prevent information

contamination, we assigned all room attendants within a hotel to

the same condition. Four hotels were assigned to the informed

2 This information is based on extensively researched recommendations for

exercise and calorie expenditure made by the CDC, American College of Sports Medicine, and Surgeon General (Pate, Pratt, Blair, et al., 1995, as cited in CDC, 1996).

3 All of the written information was translated into Spanish, and each hotel

had a designated and qualified supervisor to translate the verbal information and instruction to the subjects.

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condition, and three were assigned to the control condition. The

hotels were matched for similarity: The two same-franchise

hotels, the two condominium-type hotels, and the two unique,

luxury hotels were in different conditions. The hotels did not

differ with respect to managerial structure, and all followed the

Equal Employment Opportunity (EEO) codes and did not dis-

criminate on the basis of age, gender, ethnic background, reli-

gious background, or sexual orientation, although all subjects

in this study were female. No information regarding subjects’

characteristics (age or ethnicity) was known when the hotels

were assigned to the conditions.

In total, 84 subjects completed both sets of measures (44 in

the informed group, 40 in the control group). The subjects’ ages

ranged from 18 to 55 years, and most were Hispanic, although

some were Caucasian, African American, and Asian. All worked

32 to 40 hr per week and cleaned approximately 15 rooms per

day. Statistical analysis revealed that at the onset of the inves-

tigation, the groups did not differ significantly except in age. 4

This unexpected difference was controlled for in all analyses.

Procedure

All subjects were told that the purpose of the study was to find

ways to improve the health and happiness of women in a hotel

workplace. Each subject was given a questionnaire, and while

the subjects were filling it out, they were taken one at a time to

complete their physiological measures. The informed group was

then given the information about how their work is good exer-

cise; this information was conveyed in the form of a verbal

presentation, through individual handouts, and on larger posters

tacked to the bulletin boards in their lounge in the hope that they

would be reminded of how much exercise they were getting each

day. The control group was not given this information.

Four weeks later, we returned to take the same measures, and

all subjects were debriefed both orally and in writing. Each

session took approximately 1 hr.

Measures

Self-Reported Exercise

The study was designed to instigate an increase in perceived

exercise independent of actual exercise. Self-reported exercise

was assessed through a series of questions. First, subjects were

asked to check ‘‘yes’’ or ‘‘no’’ to indicate whether or not they

exercised regularly (perceived regular exercise). Second, they

used a scale from 0 to 10 to rate how much exercise they got

(perceived amount of exercise). Following these questions, they

were asked to describe how they got their exercise. These de-

scriptions were used for the measures of perceived work as ex-

ercise (i.e., whether or not subjects referenced their work) and

exercise outside of work (i.e., whether or not subjects named

activities such as swimming, running, doing sit ups, or other

non-work-related activities). Additional questions asked how

often subjects attended a gym and whether or not they walked to

work each day.

It was assumed, and later confirmed by the hotel house-

keeping managers, that the workload of the room attendants

remained constant in the 30 days prior to and the 30 days during

the study. Therefore, if there was no increase in reported exer-

cise outside of work, any increase in perceived regular exercise,

perceived amount of exercise, or perceived work as exercise

would be assumed to reflect a change in mind-set initiated by the

intervention and not due to an increase in actual exercise.

Dependent Variables: Physiological Measures

Weight and percentage of body fat were measured using the

Tanita Body Fat Monitor/Scale (Model UM-026, Tanita Manu-

facturing Co., Tokyo, Japan). In addition to giving a normal

weight reading (to the closest 1/10 pound), this model measures

body fat using a simplified version of bioelectrical impedance

analysis that uses leg-to-leg bioimpedance analysis. After

weight and impedance are measured, computer software (a

microprocessor) embedded in the product uses the measured

impedance, the subject’s weight, and the subject’s gender,

height, and age (which are entered in) to determine the per-

centage of body fat and body water, according to equation for-

mulas. Tanita’s standard formulas have been derived by multiple

regression analysis, using the institutional standard, dual-en-

ergy x-ray absorptiometry (DEXA), as a reference. 5

Body mass index (BMI) was calculated after the fact using the

following equation: [(weight in pounds)/(height in inches � height in inches)] � 703. BMI expresses weight as adjusted for height.

Waist-to-hip ratio (WHR) was measured by a tape measure

and calculated as the waist circumference divided by the hip

circumference. Waist measurements were taken at the midpoint

between the upper iliac crest and lower costal margin in the

midaxillary line (the narrowest point of the waist). Hip cir-

cumference was measured at the largest point around the but-

tocks or gluteofemoral fold.

Blood pressure (BP) was measured using the HEM-711AC

OMRON Automatic Blood Pressure Monitor with IntelliSense

(Omron Co., Tokyo, Japan). The OMRON monitor uses the

oscillometric method of BP measurement, detecting blood’s

movement through the brachial artery and converting it to a

digital reading of systolic and diastolic blood pressure.

4 Subjects in the informed group (mean age 5 34.12, SD 5 9.23) were sig-

nificantly younger than subjects in the control group (mean age 5 42.40, SD 5 12.54), F(1, 81) 5 11.86, prep 5 .986.

5 Initial and final measurements were taken at the same time of day (morning).

(Body-fat readings are normally highest in the morning; therefore, because measures were taken in the morning, these readings may be higher than nor- mal.) In addition, measures were taken 4 weeks apart to eliminate the hydration fluctuation involved in a woman’s menstruation cycle. Clothing weight was accounted for by virtue of the fact that the women wore the same uniforms at the two sessions.

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Dependent Variables: Behavioral Measures

In addition to assessing changes in exercise outside of work

(including gym attendance, walking to work, or other non-work-

related physical activities), we assessed substance abuse and

diet through questions asking subjects to reflect on their habits

over the past 30 days, including how much they ate relative to

their normal intake, how many cigarettes they smoked, how

many servings of vegetables and sugary foods they ate, and how

many glasses of caffeinated beverages, alcoholic beverages, and

water they drank.

RESULTS

Change in Self-Reported Exercise

Subjects’ self-reported exercise was examined using 2 (time:

Time 1, Time 2; within subjects) � 2 (condition: control, in- formed; between subjects) repeated measures analyses of vari-

ance (ANOVAs). These analyses yielded no significant effects

for exercise outside of work. Perceived amount of exercise,

however, showed main effects of time, F(1, 65) 5 6.80, prep 5

.955, Z2 5 .10, and condition, F(1, 65) 5 4.79, prep 5 .910, Z 2

5 .07, which were qualified by a significant interaction, F(1, 65)

5 6.34, prep 5 .955, Z 2 5 .09 (see Table 1). Simple effects tests

demonstrated that subjects in the informed condition reported

higher levels of perceived amount of exercise at Time 2 than did

subjects in the control condition, t(38) 5 6.72, prep > .99,

whereas there were no significant differences between condi-

tions at Time 1, t(52) 5 0.40, prep 5 .749. Similar results were

found for perceived regular exercise and perceived work as

exercise. Thus, the experimental group increased their per-

ceived exercise over the course of the study, whereas the control

group did not, and neither group increased their actual levels of

activity. Table 1 shows the means and standard deviations for

these changes, which are illustrated graphically in Figure 1.

Change in Dependent Variables: Physiological Measures

Repeated measures 2 (time: Time 1, Time 2; within subjects) � 2 (condition: control, informed; between subjects) ANOVAs

yielded a significant interaction effect for weight, F(1, 71) 5

10.89, prep 5 .984, Z 2 5 .13; percentage of body fat, F(1, 49) 5

7.31, prep 5 .958, Z 2 5 .13; BMI, F(1, 67) 5 7.344, prep 5 .958,

Z2 5 .10; WHR, F(1, 67) 5 7.46, prep 5 .961, Z 2 5 .10; and

systolic BP, F(1, 67) 5 7.34, prep 5 .958, Z 2 5 .10. No signif-

icant differences were found in diastolic BP. Table 1 presents the

means and standard deviations of these variables, which are

illustrated graphically in Figure 2.

Change in Dependent Variables: Behavioral Measures

As mentioned, repeated measures ANOVAs yielded no signifi-

cant effects for subjects’ responses regarding exercise outside of

work. Similarly, there were no significant changes in subjects’

substance abuse and diet.

DISCUSSION

Mind-Set Matters

This study did not test the placebo effect in the traditional

manner, in which expectations are aroused through inert pills or

sham procedures. Rather, subjects were actually engaging in a

behavior that is clinically proven to have positive effects on the

physiological variables measured (e.g., CDC, 1996; Hubert,

Feinleib, McNamara, & Castelli, 1983; Lee, Manson, Henne-

kens, & Paffenbarger, 1993; Press, Freestone, & George, 2003;

Raglan & Morgan, 1987; Schnohr, Scharling, & Jensen, 2003;

Tipton, 1984). To determine if the placebo effect plays a role in

the benefits of exercise, this study investigated whether sub-

jects’ mind-set (in this case, their perceived levels of exercise)

could inhibit or enhance the health benefits of exercise inde-

pendently of actual exercise.

Although it is clear that the room attendants studied met or

exceeded the Surgeon General’s recommendations for physical

TABLE 1

Self-Reported Exercise and Significant Dependent Variables by

Time and Condition

Dependent measure and group Time 1 Time 2

Self-reported exercise

Perceived amount of exercise

Informed 3.76 (3.41) 5.74 (3.48)nnn

Control 3.17 (3.42) 3.21 (2.67)

Perceived regular exercise

Informed 0.42 (0.5) 0.68 (0.5)nn

Control 0.39 (0.5) 0.36 (0.5)

Perceived work as exercise

Informed 0.29 (0.4) 0.45 (0.5)nn

Control 0.23 (0.4) 0.15 (0.4)

Physiological variables

Weight

Informed 145.5 (22.4) 143.72 (22.7)nnn

Control 146.92 (23.2) 146.71 (23.0)

Body mass index

Informed 26.05 (3.8) 25.70 (3.8)nnn

Control 26.89 (4.8) 26.86 (4.8)

Body-fat percentage

Informed 34.84 (6.3) 34.34 (6.3)n

Control 35.71 (4.9) 35.89 (4.79)

Waist-to-hip ratio

Informed 0.834 (0.05) 0.826 (0.06)nn

Control 0.853 (0.06) 0.855 (0.06)

Systolic blood pressure

Informed 129.55 (24.3) 119.9 (19.8)nn

Control 128.87 (22.1) 127.27 (21.73)

Diastolic blood pressure

Informed 79.55 (17.48) 74.88 (14.47)n

Control 77.80 (12.85) 75.03 (11.60)

Note. Standard deviations are given in parentheses. Paired-sample t tests indicated that on each of these variables, the informed group differed sig- nificantly between Time 1 and Time 2 (np < .05, nnp < .01, nnnp < .001).

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activity, initial measures suggest that the subjects were not

aware that their work is good exercise. At the onset of the ex-

periment, 66.6% of subjects reported not exercising regularly,

and 36.8% reported not getting any exercise. Interestingly, the

health of the room attendants reflected their perceived levels of

exercise rather than their actual levels: According to their initial

physiological measures, the subjects were at risk with respect to

BP, BMI, percentage of body fat, and WHR—all important in-

dicators of health. These results suggest the possibility that at

the onset of the study, the room attendants were not receiving the

Fig. 1. Changes in self-reported exercise as a function of time and group. Bars denote standard errors of the means.

Fig. 2. Changes in physiological dependent variables as a function of time and group. Bars denote standard errors of the means. BMI 5 body mass index.

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full benefits of their exercise because they were not aware that

they were getting exercise at work. Of course, there may have

been many confounding reasons (e.g., genetics or diet) why these

women were unhealthy despite their intense activity levels.

Over the course of the study, the percentage of informed

subjects who reported exercising regularly (perceived regular

exercise) doubled (39.4% to 79.4%), and the average amount of

exercise that subjects in the informed group believed them-

selves to be getting (perceived amount of exercise) increased by

more than 20%. It is important to note that although the in-

formed room attendants did report higher levels of exercise at

the end of the study, they did not report getting any additional

exercise outside of work. In addition, although the subjects in

the informed group showed a significant increase in recognizing

their work as a form of exercise, their actual workload did not

change. Thus, the changes in reported physical activity appear

to be attributable not to actual increases in physical activity, but

to a shift in mind-set initiated by the information given to them in

the intervention.

This shift in mind-set in the informed group was accompanied

by remarkable improvement in physiological measures associ-

ated with exercise. After only 4 weeks of knowing that their work

is good exercise, the subjects in the informed group lost an av-

erage of 2 pounds, 6 lowered their systolic BP by 10 points,

7 and

were significantly healthier as measured by body-fat percent-

age, BMI, and WHR. These were small but meaningful changes

given the state of health the subjects were in, especially con-

sidering that the change occurred in just 4 weeks. All of these

changes were significantly greater than the changes in the

control group. These results support our hypothesis that in-

creasing perceived exercise independently of actual exercise

results in subsequent physiological improvements.

But How?

How exactly did the change in mind-set bring about such sig-

nificant physiological changes? Conventional science assumes

that in order for weight to be lost and body fat to be reduced,

certain biological and physiological events must also take place.

In the case of BP, it is assumed that it is lowered during exercise

because the peripheral blood vessels are dilated, and that, over

time, the attenuating effect of exercise on the sympathetic

nervous system’s activity helps to reduce rennin-angiotensin

system activity, reset baroreceptors, and promote arterial va-

sodilation (which helps to control BP; CDC, 1996). In the case of

weight, it is assumed that exercise helps to reduce body fat by

increasing energy expenditure: To the extent that energy ex-

penditure exceeds caloric intake, the result is weight loss

(theoretically, about 1 pound of fat energy is lost for each

additional 3,500 kilocalories burned; CDC, 1996).

Given this knowledge, one interpretation of our results re-

garding the relationship between increased perceived exercise

and improved health would be that they were mediated by a

change in behavior. The data collected in this study, however, do

not support this conclusion. As mentioned, the room attendants

did not report any increase in exercise outside of work, nor did

they experience any increase in workload over the course of the

study. In addition, the subjects reported their habits had not

changed over the past 30 days with respect to how much they ate

(including servings of sugary foods and vegetables) and how

much they drank (caffeine, alcohol, and water). Thus, neither

increased exercise nor decreased caloric intake was reported

by the subjects.

Of course, it is possible that the room attendants actually did

change their behavior—actually did cut back on calories, im-

prove the quality of the food they ate, or work harder or more

energetically—but did not report such changes. 8 However,

previous research has found it very difficult to change behavior

of this sort (Deutschman, 2005). Thus, even if these behavioral

changes did occur as a result of the intervention, that too would

make these results interesting.

In summary, the data collected in this study, coupled with

previous research indicating the difficulty of changing behavior,

make it unlikely that the relationship between mind-set and

improvements in health was mediated by a change in behavior.

In either case, whether the change in physiological health was

brought about directly or indirectly, it is clear that health is

significantly affected by mind-set.

IMPLICATIONS AND FUTURE RESEARCH

The results of this study provide another example of the power of

the placebo effect. The moderating role of mind-set and its

ability to enhance health should be identified further, substan-

tiated, and utilized. The present results may have particular

relevance for treating diseases associated with a sedentary

lifestyle.

There is still no generally accepted, scientifically grounded

model substantiating the relationship between mind-set and

health, although several models have been proposed (see Lov-

allo, 2005). The present findings warrant investigation in this

area.

6 The fact that these subjects significantly reduced body-fat percentage in

addition to significantly losing weight makes the weight loss even more im- portant because it indicates that these women lost body fat rather than water weight.

7 In an effort to make BP readings as reliable as possible, we controlled for

several variables that are known to cause fluctuation: substance abuse (subjects reported no significant changes in alcohol, caffeine, or tobacco use during the study), diet (subjects reported no significant change in diet), time of day (BP was taken at the same time of day in the two sessions), hormonal regulation (BP was taken 4 weeks apart to control for fluctuation due to menstruation), heart rate (there was no significant difference in heart rate between Time 1 and Time 2), and immediate physical activity (BP was measured both times after subjects had been sitting for at least 10 min, to ensure that resting BP was measured).

8 Future research might benefit from using measures (e.g., pedometers, food

journals, or other people’s assessment of diet and activity levels) to enhance control for these variables.

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People have mindlessly overlooked what it means that pla-

cebos are inert. Ultimately, each individual is responsible for

their effects. Recognizing this suggests that it is time for us all to

explore more direct means of controlling our health, such as

pursuing mindfulness (see Langer, 1989) as a tool to actively and

deliberately change our mind-sets.

Acknowledgments—The authors wish to thank Cathy Crum,

Maja Dijikic, Adam Grant, and Carey Morwedge for their

comments on this manuscript.

REFERENCES

Benson, H., & Friedman, R. (1996). Harnessing the power of the

placebo effect and renaming it ‘‘remembered wellness.’’ Annual Review of Medicine, 47, 193–199.

Benson, H., & McCallie, D.P. (1979). Angina pectoris and the placebo

effect. The New England Journal of Medicine, 300, 1424–1429. Blakeslee, S. (1998, October 13). Placebos prove so powerful even

experts are surprised. New York Times Science Times, F1. Brody, H. (1980). Placebos and the philosophy of medicine. Chicago:

University of Chicago Press.

Centers for Disease Control and Prevention. (1996). Physical activity and health: A report of the Surgeon General. Atlanta, GA: U.S. Department of Health and Human Services.

Desharnais, R., Jobin, J., Cote, C., Levesque, L., & Godin, G. (1993).

Aerobic exercise and the placebo effect: A controlled study.

Psychosomatic Medicine, 55, 149–154. Deutschman, A. (2005). Change or die. Fast Company, 94, 53. Hahn, R.A. (1997). The nocebo phenomenon: Scope and foundations.

In A. Harrington (Ed.), The placebo effect: An interdisciplinary exploration (pp. 56–76). Cambridge, MA: Harvard University Press.

Hahn, R.A., & Kleinman, A. (1983). Belief as pathogen, belief as

medicine: ‘‘Voodoo death’’ and the ‘‘placebo phenomenon’’ in

anthropological perspective. Medical Anthropology Quarterly, 14, 16–19.

Hubert, H.B., Feinleib, M., McNamara, P.M., & Castelli, W.P. (1983).

Obesity as an independent risk factor for cardiovascular disease:

A 26 year follow-up of participants in the Framingham Heart

Study. Circulation, 67, 968–977. Idler, E., & Kasl, S. (1991). Health perceptions and survival: Do global

evaluations of health status predict mortality? Journals of Ger- ontology, 46(2), S55–S65.

Kaplan, G.A., & Camacho, T. (1983). Perceived health and mortality:

A nine-year follow-up of the Human Population Laboratory co-

hort. American Journal of Epidemiology, 177, 292–304. Kirsch, I., & Sapirstein, G. (1998). Listening to Prozac but hearing

placebo: A meta-analysis of antidepressant medication. Prevention & Treatment, 1, Article 0002a. Retrieved November 10, 2004, from http://journals.apa.org/prevention/volume1/pre0010002a.html

Langer, E. (1989). Mindfulness. Cambridge, MA: Perseus Books Group.

Lee, I.M., Manson, J.E., Hennekens, C.H., & Paffenbarger, R.S.

(1993). Body weight and mortality: A 27 year follow up of middle

aged men. Journal of the American Medical Association, 270, 2823–2828.

Lovallo, W. (2005). Stress and health: Biological and psychological interactions. Thousand Oaks, CA: Sage.

Nesbitt Shanor, K. (1999). The emerging mind: New research into the meaning of consciousness, based on the Smithsonian Institution lecture series. Los Angeles: Renaissance Books.

Plante, T.G., Lantis, A., & Checa, G. (1998). The influence of per-

ceived versus aerobic fitness on psychological health and

physiological stress responsivity. International Journal of Stress Management, 5, 141–156.

Plante, T.G., & Rodin, J. (1990). Physical fitness and enhanced psy-

chological health. Current Psychology: Research and Reviews, 9(1), 3–24.

Press, V., Freestone, I., & George, C.F. (2003). Physical activity: The

evidence of benefit in the prevention of coronary heart disease.

Quarterly Journal of Medicine, 96, 245–251. Raglan, J.S., & Morgan, W.P. (1987). Influence of exercise and quiet

rest on state anxiety and blood pressure. Medicine and Science in Sports and Exercise, 19, 456–463.

Roberts, A.H., Kewman, D.G., & Mercie, L. (1993). The power of

nonspecific effects in healing: Implications for psychosocial and

biological treatments. Clinical Psychology Review, 13, 375–391. Schnohr, P., Scharling, H., & Jensen, J. (2003). Changes in leisure time

physical activity and risk of death: An observational study of

7,000 men and women. American Journal of Epidemiology, 158, 639–644.

Spiro, H.M. (1986). Doctors, patients, and placebos. New Haven, CT: Yale University Press.

Tipton, C.M. (1984). Exercise, training and hypertension. Exercise and Sports Science Reviews, 12, 245–306.

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