7
The Presence or Absence of Light in the REST Experience:
Effects on Plasma Cortisol, Blood Pressure and Mood
Gina Ewy, Peter Sershon and Thomas Freundlich
ABSTRACT
This study examined the effect of light on relaxation associated with
flotation restricted environmental stimulation therapy (REST), as measured
by plasma cort i so 1, mean arteri a1 pressure, and psychometri c parameters.
Twenty subjects were paired by baseline cortisol levels into two groups; one
experiencing flotation REST in the presence of 1ight (REST -L) and one
experiencing flotation REST in the absence of light (REST-D). Subjects were
fifteen male and six female students aged 22-28 in normal health and naive
to REST. Repeated flotation REST (8 sessions) either with light or without
light was associated with a decrease in plasma cortisol and a decrease in
mean arterial pressure, with no differences in effectiveness between groups.
The psychometric assessment of mood using the POMS scale, before and after
sessions 1 and 8 revealed mood state improvement in both REST-L and REST-D
groups. These data suggest that the presence of light did not compromise the
flotation REST experience, as evidenced by the lack of difference between
REST-L and REST-D groups.
INTRODUCTION
It is well known that the body's response to various stressors is
mediated by important and complex homeostatic mechanisms. Although these
mechanisms are primarily beneficial, chronic stress can lead to disruption
of the regulatory processes governing them. Such disregulation may result
in harmful physiological and psychological manifestations.
Chronic
elicitation of the stress response has been associated with a number of
disease states (Basmajian, 1985), including gastrointestinal ulcerations,
migraine headaches, hypertension, and coronary artery disease. Therefore,
procedures potentially evoking a state of relaxation and stress attenuation
deserve investigation.
The importance of stress management relative to the prevention of
disease and overall well-being has lead to the development of nonpharmacological (biobehavioral) relaxation techniques.
The benefit of
93
P. Suedfeld et al. (eds.), Restricted Environmental Stimulation
© Springer-Verlag New York Inc. 1990
biobehavioral treatment over pharmacological treatment is two-fold. First,
with the former treatment the system reregulates internally, to correct the
problems rather than masking the problem or its symptoms with an external
agent. Secondly, biobehavioral treatment avoids the issue of drug sideeffects. Procedures reported to induce deep relaxation include biofeedback
(Basmajian, 1985), transcendental meditation (Wallace and Benson, 1972), and
short-term REST (Restricted Environmental Stimulation Therapy) (Fine and
Turner, 1985).
Early studies with restricted environment concentrated on behavioral
and physiological effects of long-term sensory deprivation and were endurance
ori ented. Subjects reported high stress states and exhi bited increased
sympathetic nervous system stimulation and elevated adrenocortical activity
(Zubek, 1969).
However, data collected in these studies indicated a
relaxation effect associated with short-term (less than 1 hour) sensory
deprivation. Lilly (1977) and others (Suedfeld et al., 1983; Turner &Fine,
1983; Green et al., 1980) reported a deep relaxation effect in subjects using
brief, repeated flotation isolation.
Previous data have demonstrated that relaxation is associated with a
decrease in activity of the adrenal axis (Davidson et al., 1979; Michaels et
al., 1979; Jevning et al., 1978; McGrady et al., 1981). Plasma cortisol can
be measured as an indicator of this axis, and levels have been shown to
decrease during REST (Turner & Fine, 1983; Turner & Fine, 1987).
In
addition, a decrease in blood pressure has been a common finding in previous
studies (Jacobs et al., 1985; Fine &Turner, 1985; Kristeller et al., 1982;
Suedfeld et al., 1982), indicating that, along with plasma cortisol, blood
pressure can be a rel iable effective index of the REST effect. Other
measurements that have been used to assess relaxation associated with REST
include heart rate, muscle tension, plasma ACTH, galvanic skin response, and
subjective reports (reviewed, Turner & Fine, 1985).
Some studies have been concerned with applications of REST treatment,
examining the clinical effectiveness of this technique in treating
hypertension (Fine & Turner, 1982), pain (Fine & Turner, 1985), autism
(Suedfeld &Schwartz, 1983), and in some addictions (Suedfeld &Baker-Brown,
1986; Adams et al., 1987). Results concerning the use of REST therapy in
stress management have been encouraging, yet the underlying mechanism is
unknown, and no studies to date have addressed the question of which
parameters of the flotation REST condition are necessary for the deep
94
relaxation response to occur.
The present study begins a series of
experiments to investigate the mechanism of the flotation REST effect.
This study examines the effect of light on the REST experience. We
hypothesized that the presence of light, by compromising the sensory
restriction, would diminish the relaxation associated with REST as measured
by plasma cortisol, mean arterial pressure and psychometric data. This was
tested by comparing the across-treatment effects of repeated, brief REST in
subjects exposed to REST with light and subjects exposed to REST without
light.
MATERIALS AND METHODS
Subjects
Twenty-one healthy volunteers, ages 22-28, were recruited from a class
of medical school students. Fifteen subjects were male, and six were female.
None of the subjects had experienced relaxation training previously. All
subjects were told they were participating in a study of physiological
changes associated with relaxation.
Subjects were paired by basel ine
cortisol levels into two groups - one experiencing relaxation in a flotation
REST environment in the presence of light (REST-L) and one experiencing the
same relaxation procedure using flotation REST in the absence of light (RESTO). There were no drop-outs during the study.
Design
The study cons i sted of three phases: a two-week peri od of basel i ne
with blood samples taken biweekly for cortisol measurement, a two-week
treatment period of two REST sessions per week, and a two-week treatment
period of two REST sessions per week with blood samples for cortisol
measurement taken on each of four non-session days.
Psychometric measures included the Taylor Manifest Anxiety Scale and
Marlowe-Crowne Social Desirability Scale administered at orientation, and the
Profile of Mood States (POMS) which was filled out before and after the first
and last treatment sessions.
Blood Sampling Procedure
Subjects were oriented regarding the blood drawing procedure which
consisted of two venipunctures from the forearm spaced twenty minutes apart
during each of eight visits. Subjects sat quietly between samplings. Heart
rate and blood pressure measurements were taken before the first blood sample
and blood pressure was again measured five minutes after the second draw.
95
All blood samp 1i ng occurred between 1200 and 1400 hours. Samples were
centrifuged at 3000 x g for ten minutes, and pl asma was separated and
refrigerated. Cortisol levels were determined by radioimmunoassay kit (Code
KCOD2, Diagnostic Products, Los Angeles, CA).
Tank Procedure
The flotation tank (Enrichment Enterprises Inc., Huntington, NY) was
an ovoid fiberglass chamber, 8 feet long, 4 feet wide and 42 inches high.
Subjects floated in a saturated epsom salt solution, specific gravity 1.28.
The tank temperature was rna i nta i ned at 94.0 ± 0.5' F. The chamber was
completely enclosed, eliminating light. For REST-L subjects a subdued light
(15 watt incandescent bulb) at the bottom of the tank illuminated the
interior and could be switched on from inside the chamber. Subjects floated
nude in a supine position.
In this position the ears were submerged,
resulting in marked reduction of sound perception.
Two flotation tanks of similar design were used, one for REST-L
subjects and the other for REST-D subjects. Orientation to tank flotation
was the same for all volunteers and cons i sted of fl otat i on techni que
information and a tour of the facility. A trained monitor was available at
all times and subjects were told they were welcome to terminate the sessions
any time they did not feel comfortable in continuing. Each tank session
consisted of: blood pressure measurement, a shower, a forty minute flotation
session, another shower, and blood pressure measurement.
Data Analysis
Data were subjected to 2 levels of analysis. Two-way repeated measures
ANOVA was used to determine differences across sessions (among weeks 1, 2,
5, and 6). Specific differences were determined by Turkey test and by ttest (Zar, 1984).
RESULTS
Cortisol
Cortisol data were subjected to repeated measures analysis of variance,
and data are presented in Figure 1.
Baseline: ANOVA established no significant difference between REST-L and
REST-D before treatment sessions began. Since no difference was found prior
to treatment sessions this allowed further measures across sessions.
Across sess ions: Repeated measures anal ys is showed no sign i fi cant difference
between REST-L and REST-D groups during post-treatment sessions.
96
171I
::>
'!<
~
..,
0
';:::"
'0tJ"
~
....,'"
,J
J
BASEUNE
II
TREATMENT
I
141
1J
,J
,,1
,JI
WEEKS
Figure 1.
Effect of REST with and without light on plasma cortisol.
Treatment values are significantly different from baseline
(light p < 0.01, dark p < 0.05). REST-L 0 - - - - - 0 (N=II),
REST-D ----- (N=10).
Treatment: Average plasma cortisol levels were significantly lower than presession levels in both REST-L and REST-D groups (light p<O.OI, dark p<0.05).
The REST-L group plasma cortisol decreased from 14.95 ± 0.57 ug/dl in
baseline to 11.72 ± ug/dl in treatment while the REST-D group plasma cortisol
decreased from 16.58 ± 0.54 ug/dl in baseline to 13.78 ± 0.51 ug/dl in
treatment.
Mean Arterial Pressure
Mean arterial pressure data were subjected to similar statistical
analysis and data are presented in Fig. 2.
Baseline: ANOVA established no significant difference between REST-L and
REST-D groups during baseline.
Across session: ANOVA showed no significant different between light and dark
REST groups during post-treatment sessions.
Treatment: Mean arterial pressures were significantly lower than baseline
in both REST-L and REST-D groups (light p <0.005, dark p <0.0003). The REST97
L group decreased from a mean arteri a1 pressure of 89.4 ± 1.76 mmHg in
baseline to 81.11 ± 1.89 mmHg in treatment while the REST-D group decreased
from a mean arterial pressure of 90.44 ± 1.64 mmHg in baseline to 80.54 ±
1.26 mmHg in treatment.
BASELINE
II
TREATMENT
90
~ 89
e
e
88
~ 87
"
~
86
g:
85
~
84
"
":z:<: 82
~ 83
<:
~ 81
80
79
78
WEEKS
Figure 2.
Effect of REST with and without light on mean arterial pressure.
Treatment values are significantly different from baseline (light
p < 0.005, dark p < 0.0003).
REST-L 0 - - - - - 0 (N=II), REST-D
(N=10).
Psychometric Measures
The Taylor Manifest Anxiety Scale (TMAS) and the Marlowe-Crowne Social
Desirability Scale (MCSDS) were filled out by subjects to predict repressive
coping styles. The criterion for repressive coping style is a score below
13 on the TMAS and a score greater than 18 on the MCSDS (Weinberger et al.,
1979). No subjects showed repressive coping strategies.
Profile of Mood States Scales were given before and after treatment
sessions one and eight, to assess effect of treatment on mood across session.
Summing all six factors in the scale (weighing tension-anxiety, depressiondejection, anger-hostility, fatigue-inertia and confusion-bewilderment
positively and vigor-activity negatively) provides a rel iable single estimate
98
of affective state (McNair et al., 1971). POMS scores showed improvement of
mood state in all sessions for both REST -L and REST -D groups (Table 1).
REST-D subjects showed a significantly greater improvement of mood state
across session one than REST-L subjects (p <0.05). There was no difference
between light and dark REST groups across the last session.
TABLE 1.
PROFILE OF MOOD STATES* FOR REST SUBJECT WITH AND WITHOUT LIGHT
POMS score**
REST-L
REST-D
*
**
***
Session 1
- 7.64 ± 2.35
-21.25 ± 6.79***
Session 8
-11.0 ± 3.47
-16.0 ± 8.68
each value is the mean change ± SE across a given session for all
subjects in respective groups.
POMS score is inversely proportional to Mood State
REST-L vs. REST-D was significantly different across session 1 (p<0.05,
t-test)
DISCUSSION
Repeated flotation REST with or without restriction of 1ight was
associated with decrease in plasma cortisol and mean arterial blood pressure
across sessions. This decrease in adrenal axis activity was consistent with
psychometric measures of mood state in these subjects as assessed by the POMS
scale. These data were also consistent with subjects' verbal reports of deep
re 1ax at ion in REST. The results of th is study and previ ous stud i es of
flotation REST (Turner & Fine, 1983; Turner & Fine, 1987; Turner & Fine,
1985) were similar in suggesting a decrease in the activity of the adrenal
axis. Blood pressure decreases in association with REST have been reported
for both hypertensive (Fine &Turner, 1982) and normotensive (Jacobs et al.,
1985) subjects, although there are two reports of no change in blood pressure
with normotensive subjects (Turner & Fine, 1987; Francis &Stanley, 1985).
However, the present study was different from previous studies in that
two REST conditions rather than a REST versus control condition were
compared. This was done in order to examine mechanisms of flotation REST
which produce the observed psychophysiological responses. We hypothesized
99
that the presence of light would disrupt the homeostatic effect of sensory
isolation, and thus diminish the relaxation associated with REST, as measured
by plasma cortisol, mean arterial blood pressure, and psychometric
parameters. The presence of light did not compromise the flotation REST
experience as evidenced by the lack of difference between REST-L and RESTO groups.
One possible explanation for these results is that the light in the
tank was serving as a monotonous stimulation, or at least insufficient
stimulation to interfere with the REST effect. Studies examining the effects
of monotonous stimulation (perceptual deprivation by continuous unpatterned
1i ght and constant "whi te" noi se) have reported effects s imil ar to studi es
using restricted environmental stimulation. However, it is unlikely that the
light condition in the present study satisfies criteria of perceptual
deprivation, since REST-L subjects reported having their eyes open
intermittently and were able to see varied and well-defined images such as
the tank ceiling, condensation droplets and well defined shadows.
An additional consideration in concluding that the presence of light
did not compromise the flotation REST experience lies in the POMS data. POMS
scores indicated an improvement of mood states for all evaluated sessions in
both REST-L and REST-D groups. Care was taken not to bias subjects toward
one condition being more powerful than the other for relaxation, and the
terms "control" and "experimental" were avoided. However, most subjects had
previously heard about REST and knew that it involved flotation in darkness.
The greater improvement of mood during session one for REST-D subjects as
compared to REST-L subjects may reflect their initial expectations (Delmonte,
1984). Since this difference did not maintain itself across sessions, the
bias may have washed out.
It is noteworthy that none of the subjects in the present study showed
repress i ve copi ng styl es as defi ned by the TMAS and the MCSDS. Previ ous
studies with a similar population of medical students (Turner &Fine, 1985)
and other studies (Schwartz, 1983) have reported that 11-25% of subjects
exhibited repressive coping style. Thus the population of the present study
may be unusually homogenous in this regard. The reason for the lack of
repressors is unknown.
The results of this study do not reveal why light did not interfere
with the REST experience. The simplest explanation would be that the
restri ct i on of 1i ght is not a crit i ca 1 component of the fl otat i on REST
100
environment. Since only one type of light at a given intensity was used, it
is possible that light of a higher intensity may affect the REST experience.
Several other model s could be considered to expl ain the underlying
mechanisms of flotation REST. Since the REST environment greatly attenuates
light, sound, temperature-awareness and kinesthetic-awareness, it is possible
that one or a combination of these conditions is responsible for the observed
phys i 01 ogi ca 1 effects. One of these models suggests the exi stence of a
threshold of sensory input which, if exceeded, will result in a compromise
of the REST effect. It may be helpful to develop a scenario to explain this
model. This scenario will assign hypothetical percentage values to those
conditions believed to be factors important to the REST experience. The
inputs to consider are 1ight, sound, temperature and flotation.
For
illustrative purposes, light will be assigned a value of 30%; sound a value
of 10%; temperature a value of 10%; and flotation a value of 50%. Thus, if
all inputs were eliminated, 100% sensory deprivation would occur. Let it
further be supposed that a threshold of 40% exists. This threshold implies
that the addition of sensory input totalling more than 40% would result in
a compromi se of the fl otat i on REST experi ence.
For example, if the
restriction of light were eliminated no compromise in the REST effect would
occur because 1ight only contributes 30% to the REST experience.
If
temperature (10%) or sound (10%) were al so added, then hypothetically a
compromise in the REST experience would occur.
Likewise, el iminating
flotation alone, (with a value of 50%) from the REST environment would
compromise the REST experience, regardless of whether light was present or
absent.
Within this model of a threshold effect, two possibilities concerning
the compromise of the REST experience must also be considered. First, if too
much sensory input is added, an "all or none" response may occur. Exceeding
the sensory input threshold would then result in a substantial compromise of
the REST effect. Second, when the threshold of sensory input is reached, it
is possible that the compromise in the REST experience would be gradual, and
proportional to the intensity and nature of the sensory input.
Another possibility which is consistent with the results of the present
study is that not all the elements of sensory deprivation are needed to have
a complete REST experience. In other words, the REST condition is not
similar to a chain which is only as strong as its weakest link. If the
weakest link model was valid, the REST subjects experiencing flotation in
101
light would have shown a compromise in their REST experience. A final model
of flotation REST suggests that REST-assisted relaxation is like a
holographic experience in which each part of sensory attenuation contributes
to the experience, but the experience is more than the sum of the parts.
Persistent activation of the stress response is known to playa role
in the process of disease. Since REST can be an effective tool in stress
management, efforts should be made to elucidate the underlying mechanisms.
The present study has shown that the presence of light does not compromise
psychophysiological measures of relaxation associated with REST and further
demonstrates the need to define in functional terms the meaning of
"restricted environment".
REFERENCES
Adams, H.B., Cooper, G.D. & Scott, J.C.
REST and Reduced Alcohol
Consumption. In: REST and Self Regulation: Proceedings of the 2nd
International Conference. (Turner and Fine, Eds.) Toledo, OH: IRIS
Publ., In Press, 1987.
Basmajian, J.V. Biofeedback Principles and Practice for Clinicians. 2nd
Ed., Baltimore, MD: Williams and Wilkins Co., 1985.
Davidson, D.M., Winchester, M.A., Taylor, C.B., Alderman, E.A. &Ingles, N.B.
Effects of Relaxation Therapy on Cardiac-Performance and Sympathetic
Activity in Patients with Organic Heart Disease.
Psychosomatic
Medicine, 1979, ii, 303-309.
Delmonte, M.M.
Physiological Responses During Meditation and REST.
Biofeedback and Self-Regulation, 1984, 2i£l, 181-200.
Fine, T.H. &Turner, J.W., Jr. The Effect of Brief Restricted Environmental
Stimulation Therapy in the Treatment of Essential Hypertension.
Behaviour Research and Therapy, 1982, 20, 567-570.
Fine, T.H. &Turner, J.W., Jr. (eds.). REST and Self-Regulation: Proceedings
of the 1st International Conference. Toledo, OH: IRIS Publ., 1985.
Fine, T.H. & Turner, J.W., Jr.
The Use of Restricted Environmental
Stimulation Therapy (REST) in the Treatment of Essential Hypertension.
In: REST and Self-Regulation: Proceedings of the 1st International
Conference. (Turner and Fine, Eds.) Toledo, OH: IRIS Publ., 136-142,
1985.
Fine, T.H. & J.W. Turner, Jr. REST-Assisted Relaxation and Chronic Pain.
IN: Health and Clinical Psychology. (Sanchez-Sosa, Ed.) New York, NY:
102
Elsevier Science Publ. Co., 1985, 511-520.
Francis, W.D. & Stanley, J.M. The Effects of Restricted Environmental
Stimulation on Physiological and Cognitive Indices. In: REST and
Self-Regulation: Proceedings of the 1st International Conference.
(Turner and Fine, Eds.) Toledo, OH: IRIS Publ., 1985, 40-49.
Green, E.E., Green, A.M. &Norris, P.A. Preliminary Report on a New Non-Drug
Method for Control of Hypertension. Journal of South Carolina Medical
Association, 1980, §i1l, 126-137.
Jacobs, G.D., Heilbronner, R.L. & Stanley, J.M. The Effects of Short Term
Floatation REST on Relaxation: A Controlled Study. In: REST and SelfRegulation: Proceedings of the 1st International Conference. (Turner
and Fine, Eds.) Toledo, OH: IRIS Publ., 1985, 179-185.
Jevning, R., Wilson, A. & Davidson, J.M. Adrenocortical Activity During
Meditation. Hormones and Behavior, 1978, 10, 54-60.
Kristeller, J., Schwartz, G.E. & Black, H.
The Use of Restricted
Environmental Stimulation Therapy in Treatment of Essential
Hypertension: Two Case Studies. Behaviour Research and Therapy, 1982,
20, 561-566.
Lilly, J. The Deep Self. New York, NY: Simon and Schuster, 1977.
McGrady, A.V., Yonker, R., Tan, S.Y., Fine, T. &Woerner, M. The Effect of
Biofeedback-Assisted Relaxation Training on Blood Pressure and Selected
Biochemical Parameters in Patients with Essential Hypertension.
Biofeedback and Self-Regulation, 1981, §i1l, 343-353.
McNa i r, D., Lorr, M. & Dropp 1eman, L. EITS Manual for Profi 1e of Mood
States. San Diego, CA: Education and Industrial Testing Service, 1971.
Michaels, R.R., Huber, M.J. & McCann, D.S. Evaluation of Transcendental
Meditation as a Method of Reducing Stress. Science, 1976, 192, 12421244.
Schwartz, G.
Disregulation Theory and Disease:
Applications to the
Repression/Cerebral Disconnection/Cardiovascular Disorder Hypothesis.
International Review of Applied Psychology, 1983, 32, 95-118.
Suedfeld, P., Roy, C. & Landon, B.P. Restricted Environmental Stimulation
Therapy in the Treatment of Essential Hypertension. Behaviour Research
&Therapy, 1982, 20, 567-570.
Suedfe 1d, P. & Schwartz, G. REST as a Treatment for Aut i st i c Chil dren.
Journal of Developmental and Behavioral Pediatrics, 1983, i, 196-201.
Suedfeld, P., Ballard, E.J. &Murphy, M. Water Immersion and Flotation: From
103
Stress Experiment to Stress Treatment.
Journal of Environmental
Psychology, 1983, 1, 147-155.
Suedfeld, P. & Baker-Brown, G. Chamber REST and Aversive Conditioning in
Smoking Cessation: Active and Placebo Effects. Behaviour Research and
Therapy, 1986, £iiil, 421-428.
Turner, J.W., Jr. & Fine, T.H. Effects of Relaxation Associated with Brief
Restricted Environmental Stimulation Therapy (REST) on Plasma Cortisol,
ACTH and LH. Biofeedback and Self-Regulation, 1983, ~, 115-126.
Turner, J.W., Jr. & Fine, T.H. Hormonal Changes Associated with Restricted
Envi ronmental St imul at i on Therapy.
IN: REST and Self-Regul at ion:
Proceedi ngs of the 1st Internati onal Conference. (Turner and Fi ne,
Eds.) Toledo, OH: IRIS Publ., 1985, 17-39.
Turner, J.W., Jr. & Fine, T.H.
Effects of Restricted Environmental
Stimulation Therapy (REST) on Self-Control of Heart Rate. In: Health
and Clinical Psychology. (Sanchez-Sosa, Ed.) New York, NY: Elsevier
Science Publ. Co. Inc., 1985, 477-490.
Turner, J.W., Jr. & Fine, T.H.
Effects of Biobehaviorally-Assisted
Re 1ax at ion Tra i ni ng on Blood Pressure and Hormone Levels, and Thei r
Variation in Normotensives and Essential Hypertensives. In: REST and
Self-Regul at ion: Proceedi ngs of the 2nd International Conference on
REST. (Turner and Fine, Eds.) Toledo, OH: IRIS Publ., In Press, 1987.
Wallace, R. &Benson, H. The Physiology of Meditation. Scientific American,
1972, 225, 84-90.
Weinberger, D., Schwartz, G. &Davidson, R. Low-Anxious, High-Anxious, and
Repressive Coping Styles: Psychometric Patterns and Behavioral and
Physiological Responses to Stress. Journal of Abnormal Psychology,
1979, 88, 369-380.
Zubek, J.B. Sensory Deprivation: 15 Years of Research. New York, NY:
Appleton-Century-Crofts, 1969.
104