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R E S E A R C H A R T I C L E Open Access
Beneficial effects of treatment with sensory
isolation in flotation-tank as a preventive
health-care intervention –arandomized
controlled pilot trial
Anette Kjellgren
1,2*
and Jessica Westman
1
Abstract
Background: Sensory isolation in a flotation tank is a method known for inducing deep relaxation and subsequent
positive health effects for patients suffering from e.g. stress or muscle tensions pains. Very few studies have investigated
this method as a preventive health-care intervention. The purpose of this study was to evaluate the effects in healthy
participants after receiving a series of flotation tank treatment.
Methods: Sixty-five participants (14 men and 51 women) who were all part of a cooperative-health project initiated by
their individual companies, were randomized to either a wait-list control group or a flotation tank treatment group
where they participated in a seven weeks flotation program with a total of twelve flotation sessions. Questionnaires
measuring psychological and physiological variables such as stress and energy, depression and anxiety, optimism, pain,
stress, sleep quality, mindfulness, and degree of altered states of consciousness were used. Data were analysed by
two-way mixed MANOVA and repeated measures ANOVA.
Results: Stress, depression, anxiety, and worst pain were significantly decreased whereas optimism and sleep quality
significantly increased for the flotation-REST group. No significant results for the control group were seen. There was
also a significant correlation between mindfulness in daily life and degree of altered states of consciousness during the
relaxation in the flotation tank.
Conclusions: It was concluded that flotation-REST has beneficial effects on relatively healthy participants.
Trial registration: Australian New Zealand Clinical Trials Registry: ACTRN12613000483752.
Keywords: Flotation tank, Flotation, Relaxation response, Stress, Health, Sick leave
Background
Stress-related ill-health such as depression, anxiety, and
insomnia are all common reasons for sick-leave absence
from work [1,2] and stress-related illnesses have been
studied in workplace settings [3-5]. Stress-related symp-
toms found amongst many employees include fatigue,
burnout syndrome and gastric complaints [6] Stress,
which is the most common reason for sick-leave absence
[2,3], may increase the number of days in sick-leave
[4,5], reduce productivity [5], and increase the risk of
psychiatric disorders [7].
Occupationally induced fatigue play a major role in
work-related psychological illnesses and research show
that insufficient opportunities to recover from work fa-
tigue contribute to stress-related illnesses [4]. One way
of recovering from and/or preventing stress-related ill-
nesses could be through health promoting programs at
work places [4,5] where relaxation techniques are used
as a method. Health-care programs, including methods
of stress-reduction such as relaxation, may be of such
importance it will affect the number of sick-leave days
[5]. Finding an effective method that can be imple-
mented at work places might help individuals to find
tools to prevent ill health and psychological negative fac-
tors. Evidence shows a positive effect on sick leave when
* Correspondence: Anette.Kjellgren@kau.se
1
Human Performance Laboratory, Karlstad University, Karlstad, Sweden
2
Department of Psychology, Karlstad University, SE-651 88 Karlstad, Sweden
© 2014 Kjellgren and Westman; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the
Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly credited.
Kjellgren and Westman BMC Complementary and Alternative Medicine 2014, 14:417
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health-care programs are implemented at work places
[5]. Unfortunately, research regarding stress-related ill-
nesses is mostly focused on those individuals already
suffering, when preventive methods might be the most
sufficient way of actually decreasing potential sick-leave
absence by increasing general health [8].
Sick leave from work creates a heavy economic burden
on the individual as well as the company, and it puts a
mental strain on the person affected, colleagues and so
on. There is a need to decrease the number of sick leave,
especially those of stress-related character since they ac-
count for a large part of the sick-leave cost [9].
The physiological process of relieving the stress reac-
tion is known as the ‘relaxation response’(RR) [10,11].
The relaxation response is attainable at a state of deep
relaxation, and is the opposite of the “fight-or-flight”re-
sponse. Why RR is such an effective remedy to stress
symptoms is due to the direct link with parasympathetic
nervous system activity where it lowers the heart rate
and blood pressure as well as reducing respiratory fre-
quency [11-13]. In order to successfully elicit the RR re-
sponse in a stressful situation, it is critical that sensory
input and bodily movements are reduced [10]. Unfortu-
nately, many people find it difficult to engage in relax-
ation exercises that will generate RR [14]. One effective
method to elicit RR is through relaxation in a flotation
tank. During flotation-REST (Restricted Environmental
Stimulation Technique) an individual lay in a horizontal
floating posture immersed in highly concentrated salt
water (magnesium sulphate) in a flotation tank. All in-
coming stimuli are reduced to a minimum during this
period (usually 45 minutes), i.e. sound and light, and the
water is heated to skin temperature. Flotation-REST has
been scientifically investigated and is today considered a
well-developed and scientifically proved method used to
reduce stress, depression, anxiety, and to increase opti-
mism and sleep quality [15-17]. Significant pain reduc-
tion has also been reported after using flotation-REST
technique [18,19]. A meta-analysis by Dierendonck and
Nijenhuis [20] concluded that flotation-REST has posi-
tive effects on physiology (e.g., lower levels of cortisol,
lower blood pressure and well-being). Flotation-REST
appears to be an effective treatment method and more
effective than other relaxation techniques included in
their study (i.e. muscle relaxation, biofeedback, and
meditation [20].
Earlier research regarding flotation-REST mainly in-
volves individuals with a diverse array of ailment, and so
there is a need to further investigate this method when
used by working professionals in order to find out if it
is a suitable method for preventing stress and stress-
related problems in healthy participants.
The purpose of this study was to evaluate psycho-
logical effects in a series of treatments of flotation-REST
in healthy participants. Based on previous studies, we
hypothesized that beneficial effect on levels of pain, de-
pression, anxiety, stress, energy, optimism and sleep
quality would occur. Would it have beneficial effects on
their health as proven in previous studies [20].
Methods
Participants
Sixty-five participants (14 men, 51 women) from three
different companies with a mean age of 47.95 years
(SD = 9.47) were included in the study. The partici-
pants were randomly assigned to a flotation-REST
group (37 persons) or a wait-list control group (28 per-
sons). Their mean number of monthly consumption of
cigarettes was 47.23 (SD = 139.75), mean monthly con-
sumption of alcohol was 172.90 millilitres (SD =203.33)
and mean number of used snuffboxes was 0.77 (SD =
2.87) every month. There were no significant differences
regarding gender, age, cigarettes, snuff or alcohol between
the two groups (independent samples t-tests, ps >0.256).
The participants were all part of a cooperative-health pro-
ject initiated by their individual companies. There was a
wide range of occupational groups varying from managers,
employers and employees all in the retail industry. The
three companies had no part in any of the practical details
regarding data collection, interpretation of results, study
design etc.
Design
A two-way split-plot design was carried out, where Time
with assessments before and after the treatment sessions
constituted the within-subject factor. Group (control group
and flotation-REST group) constituted the between-subject
factors. The participants were treated with flotation-REST
during a 7-week period with a total of 12 flotation-REST
sessions (45 min each). Several measurements (depression,
anxiety, stress, energy, sleep quality, pain, optimism) were
assessed before and after the treatment period. For the con-
trol group the same measurements were assessed before
and after a 7-week period. After the period the control
group also received flotation-REST treatment.
This study is registered as a clinical trial in Australian
New Zealand Clinical Trials Registry (ANZCTR), as
ACTRN12613000483752, and ethical approved by Karlstad
University Ethical Review Board, dnr C2013/88.
Instruments
SE - Stress and energy
This is a self-estimation instrument regarding an indi-
vidual’s energy and stress experiences [21]. It is based on
two subscales that indicate the mood levels regarding:
'experienced stress' and ‘experienced energy’. The sub-
jects are to answer certain statements that are placed on
a six-grade scales, from 0 = not at all, to 5 = very much.
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Examples of the statements are “How much do you feel
relaxed”,“How much do you feel tense”. The SE-scale is
based on an early checklist, the Mood Adjective Check-
List [22] and has been further modified and translated
into Swedish [23]. The instrument has been validated in
a number of studies i.e. [21,23]. Cronbach's alpha was
0.84 for the stress subscale, and 0.74 for the energy sub-
scale. The score range is from 0 –5 for each subscale.
HADS - Hospital anxiety depression scale
The HADS is a rating scale regarding degree of anxiety
and depression. It was constructed for use with physic-
ally ill people [24], and has been validated and reliability
tested [25]. The HAD scale consists of fourteen state-
ments with four response alternatives ranging from 0 to
3. Examples of the questions are ““Do you feel tense or
wound up?”,“Do you take as much interest in things as
you used to?”There are seven statements concerning
anxiety and seven for depression, wherein values under
6 are considered normal, those between 6 and 1 are bor-
derline, and all values over 8 points are indicative of a
probable depression or anxiety diagnosis [26]. The score
range is from 0 –21 for each subscale. Cronbach's alpha
was 0.74 for the depression subscale, and 0.82 for the
anxiety subscale.
LOT - Life orientation test
The test [27] consists of eight items plus four filler
items. The task of each participant is to decide whether
or not one agrees with each of the items described. The
scale ranges from 0 –4 where 0 indicates “strongly dis-
agree”and 4 indicates “strongly agree”; the total score
range is 0 –32. The test measures dispositional opti-
mism, defined in terms of generalized outcome expect-
ancies. Parallel Test Reliability is reported to 0.76 and
Internal Consistency to 0.76 [27] and Test-Retest reli-
ability to 0.75 [28]. LOT is also regarded as having an
adequate level of convergent and discriminant validity
[26] as demonstrated by correlation statistics and by
using LISREL VI (r= 0.64).
SQ - Sleep quality
This instrument consists of 11 questions that elucidate
the sleeping habits [29]. Responses to 9 questions are
placed on a 0–4 scale, response to one question is placed
on a 0–5 scale, and response to one further question is
placed on a 0–8 scale. Examples of the questions are
“How often do you feel tired on week days?”,“How often
do you feel you did not get enough sleep?”,“How do
you feel you usually sleep?”. The psychometric proper-
ties were examined by comparing healthy and sick
people, and using Cronbach’s alpha (alpha = 0.88) [28].
Score range is 0 –45, and Cronbach’s alpha was 0.64.
MAAS
Mindful Attention Awareness Scale is designed to assess
the main characteristic of dispositional mindfulness [30].
It measures whether a person is open or receptive to
what is happening in the present and has a mindful state
over time through a 15-item scale [30]. The instrument
consists of 15 items, all of which indicate a lack of mind-
fulness. The items are rated on a 6-point Likert scale
ranging from 1 (almost always) to 6 (almost never). If
the scores are rated high –it indicates more mindfulness
of the subject (the total score can range from 15 to 90)
[31]. Cronbach’s alpha was 0.80.
Normal pain and worst pain
Visual Analog Scale (VAS). These scales were used for
measuring normal pain and experienced worst pain.
They consisted of a 100 mm horizontal line with the an-
chors “no pain”on the left extreme and “excruciating
pain”on the right extreme. VAS is considered the “gold
standard”for assessment of clinical pain, and changes in
VAS score are regarded as significant evidence of indi-
vidual response to treatment, placebo, or experimental
manipulation [32]. The accuracy and precision have
been examined for both clinical and experimental pain,
and found adequate [33].
EDN - Experienced deviation from normal state
This is an instrument that is constructed to be used
in flotation-REST experiments based on the APZ-
questionnaire and OAVAV [34] so that an assessment of
altered states of consciousness and the relaxation re-
sponse can be made. The EDN consists of 29 questions
and these statements should each be responded to on a
VAS-scale 0–100 mm (where 0 means “No, not more
than usually”and 100 means “Yes, much more than usu-
ally”). Points obtained from these statements, are aver-
aged so that an “index of experience”(0 –100) can be
measured [16]. Through this, the total experience of de-
viation from normal states can be obtained. Examples of
statements are “It seemed to me that my environment
and I were one”and “I experienced past, present and fu-
ture as an oneness”.
In earlier studies e.g. [11,35] the EDN scale has been
used where Cronbach’s alpha measured between 0.91 –
0.97, which suggests very high reliability for this scale; in
the present study Cronbach’s alpha was 0.93. The aver-
age EDN-value following a person’s first encounter with
flotation-REST is approximately around 30. Resting on a
bed in a dark quiet room generates approximately 15
points [36].
Flotation tank
Outer measurements are 2600 × 1650 × 1330 mm. In
total it contains 600 litres of water and 350 kg’sof
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magnesium sulphate salt. To maintain a correct water
temperature (approximately outer skin temperature,
35°C), heating foil is placed in the lower section of the
floating tank, regulated by a thermostat and heated in
regular intervals. The door is outwardly opened. The
inside of the lower section had ribbed bottom to pre-
vent slipperiness. Between flotation sessions, water is
filtered and sterilized with UV-light along with weekly
addition of hydrogen peroxide where oxidization oc-
curs. The sterilization of water between flotation ses-
sions takes approximately fifteen minutes. Filters are
regularly changed and the inside of the flotation tank
is cleaned twice a week in accordance to public health
board recommendations.
Procedure
An agreement was made between the owner of a
flotation centre and three managers from three differ-
ent companies about a health-care program involving
flotation-tank treatments. All three companies adver-
tised through intranet correspondence, their company
magazines, and through emails, offering all employees
to participate in the health-care program. All inter-
ested participants were invited to an information
meeting at the flotation centre located in Deje in the
county of Varmland, Sweden, where they were further
informed about the program. Information was given
that the flotation-rest program would enable them to
participate in a scientific study concerning the effects
of this treatment program. Further information was
given regarding that the participation was voluntary,
confidential, that they would be randomly selected to
either experimental group or waiting list, and that they
could terminate their participation at any given point.
All participants made a verbal informed consent about
participating. They were also informed it was possible
to participate in the health-care program without par-
ticipation in the present study. All participants filled
out a questionnaire regarding basic facts (age, gender,
alcohol consumption, nicotine use) as well as SE, HADS,
LOT, VAS and SQ questionnaires. Data was collected by
the manager of the flotation center.
After the introduction and data collection, the enrolled
individuals were randomly assigned to either the control
group or to the flotation-REST group (a total of 12
flotation sessions). Those individuals that had been ran-
domized to the wait-list control group got the opportun-
ity to later participate in flotation-treatments after the
present study was terminated.
All participants were guided through the flotation
centre. Participants in the flotation-REST group booked
the 12 awaiting flotation sessions (around two per week
for a period of seven weeks) where each session was of
45 minutes duration and 30 minutes to shower and relax
afterwards. After the third flotation session a supple-
mentary EDN questionnaire was filled out by the experi-
ment group. After the last flotation-REST session, the
questionnaires (i.e., SE, HADS, LOT, VAS, EDN and SQ)
were once again answered by the flotation-REST group
along with a complementary MAAS questionnaire. All
questionnaires were filled out in privacy in a separate
room (no staff there) and the participant put their ques-
tionnaires in a closed box, that were later transported
un-opened to the researchers.
The control group was scheduled to return 7 weeks
later for filling in the scales SE, HADS, LOT, PAI, and
SQ again. All persons were treated in accordance with
the Declaration of Helsinki, Ethical Principles for Med-
ical Research Involving Human Subjects. Time estimated
between first announcement of health project and com-
pletion was about 6 months. The participants suffered
from no sick absence and were hence referred to as be-
ing relatively healthy.
Results
Stress-related psychological variables
A two-way mixed Pillais’MANOVA was carried out with
Time (before, after) as the within-subjects factor and Group
(flotation, control) as between-subjects factor. Dependent
variables were the psychological variables which in earlier
studies e. g. [29] have been proven to strongly intertwine,
i. e., stress (SE), energy (SE), anxiety (HADS), depression
(HADS), dispositional optimism (LOT), and sleep quality
(SQ). The analysis showed significant effects for Time
(p<0.001, Eta
2
= 0.48) and for Time × Group interaction
(p= 0.008, Eta
2
= 0.26). There was no significant effect for
Group (p= 0.248, Eta
2
= 0.13). The results from the univar-
iate F-tests are given below. For means and standard devia-
tions, see Table 1.
Stress
The analyses yielded a significant difference for Time
[F(1, 61) = 6.44, p= 0.014], and a descriptive analysis
showed that stress was reduced from 1.85 (SD =1.10)
to 1.35 (SD = 1.04) after the treatment period. There
was also a significant interaction Time x Group [F(1,
61) = 8.23, p= 0.006], and further analysis (pair-sam-
ples t-tests, 5% level) showed that the stress was re-
duced for the flotation group (t
(36)
= 4.42, p<0.001)
but not for the control group (t
(27)
=0.169,p= 0.867).
Energy
The analyses yielded a significant effect for Time [F (1, 61) =
20.70, p <0.001], where the energy was lowered from 3.27
(SD = 0.69) before the treatment, to 2.54 (SD = 0.99) after
the treatment. There was no significant interaction Time
×Group(p= 0.707) indicating both groups lowered their
energy-level in a similar way.
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Anxiety
The analyses yielded a significant difference for Time
[F(1, 61) = 19.42, p<0.001], and a descriptive analysis
showed that the anxiety was reduced from 7.54 (SD =
4.15) to 5.43 (SD = 3.3.79) after the treatment period.
There was also a significant interaction Time × Group
[F(1, 61) = 17.90, p<0.001], and further analysis
(paired-samples t-tests, 5% level) showed that anxiety was
reduced for the flotation group (t
(36)
=5.67,p<0.001) but
not for the control group (t
(27)
=0.231,p=0.819).
Depression
The analyses yielded a significant difference for Time
[F(1, 61) = 7.68, p<0.001], and descriptive analysis
showed that depression diminished from 4.24 (SD =
3.42) to 3.13 (SD = 2.73) after the treatment period.
There was also a significant interaction Time × Group
[F(1, 61) = 13.32, p= 0.001], and further analysis
(paired-samples t-tests, 5% level) showed that depression
was reduced for the flotation group (t
(36)
= 4.74,
p<0.001) but not for the control group (t
(27)
= 0.508,
p= 0.616).
Optimism
The analyses yielded a significant difference for Time
[F(1, 61) = 9.83, p= 0.003], and a descriptive analysis
indicated that optimism increased from 20.30 (SD =
5.18) to 22.27 (SD = 5.06) after the treatment period.
There was also a significant interaction Time × Group
[F(1, 61) = 10.26, p= 0.002], and further analysis
(paired-samples t-tests, 5% level) showed that optimism
was increased for the flotation group (t
(36)
= 4.36, p<0.001)
but not for the control group (t
(27)
= 0.06, p= 0.953).
Sleep quality
The analyses yielded a significant difference for Time
[F(1, 61) = 10.11, p= 0.002], and a descriptive analysis in-
dicated that sleep quality increased from 24.37 (SD =8.64)
to 27.83 (SD = 8.83) after the treatment period. There was
also a significant interaction Time x Group [F(1, 61) =
9.38, p= 0.003], and further analysis (paired-samples
t-tests, 5% level) showed that sleep quality was increased
for the flotation group (t
(36)
=3.95,p<0.001) but not for
the control group (t
(27)
= 0.323 , p= 0.749).
Correlation analyses (Pearsons’) between the variables
Stress and Sleep quality were also performed, and there
was a significant negative correlation both before
intervention (r=−0.585, p<0.001) and after interven-
tion (r=−0.507, p<0.001).
Pain variables
Two repeated measures ANOVA were carried out with
Time (before, after) as the within-subjects factor and
Group (flotation, control) as between-subjects factor.
Dependent variables were worst pain and normal pain.
See Table 2.
Pain (worst pain)
The analyses yielded a significant difference for Time
[F(1, 58) = 28.672, p<0.001] and a descriptive analysis
showed that worst pain decreased from 64.29 (SD =
28.13) to 39.70 (SD = 32.11) after treatment period.
There was also a significant interaction between Time ×
Group [F(1, 58) = 5.494, p= 0.023], where the pain
decreased from 64.29 (SD= 28.12) to 39.70 (SD = 32.11)
for the flotation group; for the control group there
were no significant differences (pain before = 64.76,
pain after = 55.15).
Pain (normal pain)
There were no significant differences or interactions for
normal pain (p>0.05).
Mindfulness and Altered states of consciousness
There was a significant correlation between Mindfulness (as
measured with MAAS) and degree of Altered states of con-
sciousness (as measured with EDN), r= 0.391, p= 0.018.
For a scatter plot for MAAS vs. EDN, see Figure 1.
Table 2 Means (and Standard deviations) for the pain
variables before and after the treatment period
Variable Control group Flotation-REST group
VAS Worst pain before 64.76 (25.14) 64.29 (28.12)
VAS worst pain after 55.15 (28.97) 39.70 (32.11)
VAS normal pain before 30.28 (21.92) 27.32 (20.12)
VAS normal pain after 25.68 (17.15) 15.00 (17.17)
Table 1 Means (and Standard deviations) for the
psychological variables before and after the treatment
period
Variable Before After Difference
SE Stress control 1.84 (1.15) 1.89 (1.04) + 0.05 n.s
SE Stress floating 1.86 (1.07) 0.95 (0.84 - 0.91 **
SE Energy control 3.44 (0.70) 2.63 (0.96) - 0.81 n.s
SE Energy floating 3.14 (0.66) 2.46 (1.02) - 0.74 n.s
HADS Anxiety control 7.03 (3.46) 6.96 (3.52) - 0.07 n.s
HADS Anxiety floating 7.92 (4.61) 4.28 (3.61) - 3.64 **
HADS Depression control 4.00 (3.41) 4.30 (2.58) + 0.30 n.s
HADS Depression floating 4.42 (3.47) 2.25 (2.53) - 2.17 **
LOT optimism control 20.96 (5.05) 20.93 (5.76) - 0.03 n.s
LOT optimism floating 19.81 (5.29) 23.28 (4.26) + 3.47 **
SQ Sleep Quality control 25.22 (9.98) 25.33 (8.87) + 0.11 n.s
SQ Sleep Quality floating 23.72 (7.55) 29.69 (8.44) + 5.97 **
** = significant effec t, p < 0.001; n.s = non signi ficant effect.
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In order to further evaluate this correlation the vari-
able EDN was divided into three parts (low, medium,
high) thereby creating the independent variable EDN-
group. Cut-off points for these levels were 33.3% and
66.7%. Analysis with one-way ANOVA with EDN-group
(low, medium, high) as the independent variable, and
MAAS as dependent variable yielded a significant differ-
ence between the groups [F(2,35) = 4.033 p= 0.027,
eta
2
= 0.39]. A post–hoc analysis (Bonferroni) showed
there was a significant difference between “low”and “high”
(p= 0.029) but not with comparison to the medium con-
dition (ps = 0.163); the persons obtaining a higher degree
of altered states of consciousness in the tank also experi-
ence more mindfulness in their daily life.
Discussion
The purpose of this study was to evaluate psychological
effects in a series of treatments of flotation-REST in
healthy participants (i.e. not being on sick-leave absence).
The main findings were significant decreased experienced
stress, worst pain, anxiety, and depression - as well as
significant increased sleep quality and optimism for the
flotation-REST group compared to the control group. In
addition, it was found that the dimensions mindfulness
and altered states of consciousness, at least to some ex-
tent, seemed to be overlapping constructs.
Flotation-REST treatment could be a valuable tool for
increased over-all wellbeing. The effect-size for the per-
formed general MANOVA-analysis showed a large ef-
fect, and therefor probably indicating a beneficial effect
of real importance. General sleep quality significantly in-
creased after flotation-REST treatment. There was also a
significant decrease in experienced stress for the flotation-
REST group, which may be a contributing factor to the
increased sleep-quality. In order to successfully fall and
stay asleep a relaxed and stress-free state is important.
There was also a significant decrease in experienced stress
for the flotation-REST group, which was directly corre-
lated with increased sleep-quality.
By having experienced deep relaxation through flotation-
REST, it could help a person to find a similar state of
relaxation in daily life. Sleep deprivation is known to have
negative effects on certain cognitive functions [37], being a
trigger for depression and other psychological diseases, as
well as reducing the immune defence [38,39]. Sleep
deprivation has also shown to be a trigger of hypertension,
heart disease, and diabetes [40,41], which are all serious
health issues. Lack of sleep is also a contributor to sick-
leave absence from work [41]. Being able to increase sleep
quality and quantity is advantageous on an individual basis
and might prevent possible sick leave. There was also a sig-
nificant lowered energy level overtime(forbothgroups);
we have no explanation for this.
Flotation-REST also decreased the experienced “worst
pain”intensity. Decreased pain in participants using
flotation-REST has been extensively described in earlier
studies e.g. [11,17,42]. Participants in this present study
were not pain patients, but did however experience
some pain in different parts of the body that apparently
diminished significantly. It can be assumed that many of
the experienced pain were due to muscle tensions, and
that the induced relaxation and stress reduction in the
tank may be a possible explanation for reducing these
pains. There were no decrease in the experienced “normal
Figure 1 Scatterplot for MAAS vs EDN.
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pain”; maybe such low-intensity pains are more due to
other reasons than muscle tensions, and therefor not af-
fected by the deep relaxation in the tank.
Degree of anxiety and depression did also significantly
decrease for the flotation-REST group during the treat-
ment weeks. Depression and anxiety are strong contrib-
utors to sick-leave and serious health problems such as
high blood pressure [40]. In addition, it was concluded
that optimism significantly increased for the flotation
group, which is a further indication of general wellbeing
and psychological health. Flotation-REST treatments seem
to enhance wellbeing and could certainly have great value
and importance as a health-care method.
Another new finding was that the dimensions mindful-
ness (as measured with MAAS) and altered states of
consciousness (as measured with EDN) seemed to be
partly overlapping constructs. Those individuals who re-
ported higher levels of altered states of consciousness
(ASC) during flotation-REST also scored high on MAAS
(and thus were open and receptive to here-and-now and
had a mindful state in daily life). To our best knowledge,
this is the first time the correlation between ASC and
mindfulness has been investigated. We have in earlier
studies [16,17,19] argued that degree of ASC in the
flotation tank is a measure of the relaxation response
and a person’s ability to feel secure. A recent review [43]
of empirical studies concludes that mindfulness is closely
associated with psychological well-being. Several studies
(e.g. [17,20] have earlier confirmed the beneficial effects
of flotation-REST, and it has been suggested that the
deep relaxation and stress reduction is the main con-
tributingfactors.Fromthepresentstudywewould
also like to suggest that flotation tank treatment facili-
tates the psychological process of increased mindful-
ness, but further studies are needed for confirming if
such causality exists.
Many of the participants wrote comments, without be-
ing asked to do so, on their individual questionnaires.
They continuously emphasized how their pain - which
many of them had been having for many years - was
practically gone after the 12-session flotation program.
They mentioned further how they felt relaxed, slept bet-
ter, and were over-all happier and healthier. Many of the
participants had prior to the floating sessions been using
a range of different methods to reduce pain, stress and
other individual health issues. Medicines, yoga, massage,
and physiotherapy were some of the treatments men-
tioned, and never had they so successfully been relieved
from pain, tension, stress etc.
Conclusions
The results of the present study indicate that flotation-
REST may reduce contributing factors to potential stress-
related illness as well as increase certain psychological
factors in healthy participants. Stress, anxiety, depression,
and worst pain decreased and sleep quality and optimism
increased in the flotation-REST group compared to the
wait-list control group. This technique might increase
general health and thus help prevent future sick leave. On
an individual basis, sick leave puts a negative strain on the
affected. Not only financially but it also tends to generate
further negative effects such as lack of career possibilities,
confidence, and a decrease of social interactions. Whether
or not flotation-REST has positive effects on reduction of
sick leave need to be evaluated in further research.
Competing interests
The authors declare that they have no competing interests.
Authors’contributions
AK carried out the design of the study, made contacts with the flotation
centre, the clinical trial registration and the ethical approvement procedure.
JW supplied the data into the statistical analysis program (SPSS). AK and JW
performed the statistical analyses, wrote the manuscript and together made
revisions and approved the final manuscript. Both authors read and
approved the final manuscript.
Received: 16 November 2012 Accepted: 15 October 2014
Published: 25 October 2014
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doi:10.1186/1472-6882-14-417
Cite this article as: Kjellgren and Westman: Beneficial effects of
treatment with sensory isolation in flotation-tank as a preventive
health-care intervention –a randomized controlled pilot trial. BMC
Complementary and Alternative Medicine 2014 14:417.
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