Content uploaded by Hubertus Sandler
Author content
All content in this area was uploaded by Hubertus Sandler on Jan 24, 2017
Content may be subject to copyright.
RESEARCH ARTICLE
Relaxation – Induced by Vibroacoustic
Stimulation via a Body Monochord and via
Relaxation Music – Is Associated with a
Decrease in Tonic Electrodermal Activity and
an Increase of the Salivary Cortisol Level in
Patients with Psychosomatic Disorders
Hubertus Sandler
1
*, Uta Fendel
1
, Petra Buße
1
, Matthias Rose
1
, Rainer Bo
¨sel
2,3‡
, Burghard
F. Klapp
1‡
1Department for General Internal and Psychosomatic Medicine, Charite
´Universia
¨tsmedizin Berlin, Berlin,
Germany, 2International Psychoanalytic University Berlin, Berlin, Germany, 3Department of Cognitive
Neuroscience, Freie Universita
¨t Berlin, Berlin, Germany
‡ These authors have emeritus status.
*hubertus.sandler@charite.de
Abstract
Vibroacoustic stimulation by a Body Monochord can induce relaxation states of various
emotional valence. The skin conductance level (SCL) of the tonic electrodermal activity is
an indicator of sympathetic arousal of the autonomic nervous system and thus an indicator
of the relaxation response. Salivary cortisol is considered to be a stress indicator of the
HPA-axis.
The effects of the treatment with a Body Monochord and listening to relaxation music
(randomized chronological presentation) on SCL and salivary cortisol in relation to the emo-
tional valence of the experience were examined in patients with psychosomatic disorders
(N = 42). Salivary cortisol samples were collected immediately before and after the exposi-
tions. Subjective experience was measured via self-rating scales.
Overall, both the exposure to the Body Monochord as well as the exposure to the relaxa-
tion music induced an improvement of patients’ mood and caused a highly significant reduc-
tion of SCL. A more emotionally positive experience of relaxation correlated with a slightly
stronger reduction of the SCL. Both treatment conditions caused a slight increase in salivary
cortisol, which was significant after exposure to the first treatment. The increase of salivary
cortisol during a relaxation state is contrary to previous findings. It is possible that the relaxa-
tion state was experienced as an emotional challenge, due to inner images and uncommon
sensations that might have occurred.
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 1 / 17
a1111111111
a1111111111
a1111111111
a1111111111
a1111111111
OPEN ACCESS
Citation: Sandler H, Fendel U, Buße P, Rose M,
Bo¨sel R, Klapp BF (2017) Relaxation – Induced by
Vibroacoustic Stimulation via a Body Monochord
and via Relaxation Music – Is Associated with a
Decrease in Tonic Electrodermal Activity and an
Increase of the Salivary Cortisol Level in Patients
with Psychosomatic Disorders. PLoS ONE 12(1):
e0170411. doi:10.1371/journal.pone.0170411
Editor: Urs M. Nater, University of Marburg,
GERMANY
Received: July 21, 2016
Accepted: January 4, 2017
Published: January 23, 2017
Copyright: ©2017 Sandler et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information
files.
Funding: The study was funded by Universita¨re
Forschungsfo¨rderung Charite
´(Universitary
Research Support Charite
´, Identification: 11/
48720)) in the period from 1.1.2011 to 31.12. 2011
with an amount of 3.800 (three thousand eight
hundred) €. The funders had no role in study
Introduction
Listening to music can promote a subjective feeling of wellbeing and induce a psychophysio-
logical relaxation response, which is characterised by a reduction of the sympathetic activity of
the autonomic nervous system. Various musical interventions in clinical settings were able to
induce reductions of heart rate, blood pressure and respiratory rate, as well as decreases in anx-
iety and improvements of mood in different patient groups [1–8]. Especially slow and soothing
music seems to facilitate the vegetative relaxation effect [9–12].
The electrodermal activity (EDA) denotes changes in the electrical skin conductance and is
regarded as an indicator for changes in the arousal of the autonomic sympathetic nervous sys-
tem. The tonic Skin Conductance Level (SCL), which comprises slow spontaneous fluctuations
of the sympathetic innerved eccrine sweat gland activity, is regarded to be a valid parameter
for a relaxation reaction and is considered to be an indicator for general arousal [13]. More-
over, the EDA is considered to be an indicator for emotion-associated sympathetic activity.
Various studies have shown a relation between the reduction of tonic SCL and the induction
of pleasant emotions, like contentment (described as feelings of wellbeing, relaxation and
peacefulness) and feelings of safety. Unpleasant emotions like anger, anxiety, fear and disgust
are associated with an increase in tonic SCL [14].
Aside from the activation of the sympathetic nervous system the release of cortisol, which is
modulated by the hypothalamic pituitary adrenal axis, is a further indicator of the psychophys-
iological stress reaction. Salivary cortisol is considered to be a valid indicator of plasma cortisol
[15] and the most common biological parameter in stress research [16]. Several studies have
shown a direct effect of different relaxation techniques (or methods) on the reduction of corti-
sol levels [17–21]. Similarly, listening to music has modulating effects on the release of cortisol.
For instance, meditation music was associated with a reduction of cortisol levels [22], listening
to music after inducing a stress reaction led to a stronger decrease of cortisol levels and listen-
ing to music during invasive medical interventions was associated with a lower increase of cor-
tisol levels [23,24].
As described in detail previously [25], the treatment with a monochord, especially the Body
Monochord is used as body-oriented music therapy, which uses vibroacoustic stimulation,
which can induce the experience of deep relaxation states and feelings of altered body percep-
tion [26–28]. The Body Monochord consists of a wooden resonance box standing on four feet,
on which the patient lies during the treatment session. Below the resonance box there are vari-
ous strings (tuned in fifth tuning). The strings are played by the therapist sitting beside the
Body Monochord. By stroking evenly across the strings with fingers of both hands a sound car-
pet with a distinct emergence of overtones is created, whereas familiar musical structural
parameters like rhythm, melody or changes in harmony are missing. In addition, there’s a sen-
sory stimulation of the patient’s body by the vibrations due to the direct physical contact with
the resonance box. Body Monochords can have different shapes, forms, and harmonical tun-
ings (e.g. fifths, octave or identical tuning) [25]. Research on therapeutic application of mono-
chord sounds and vibroacoustic stimulation via Body Monochord has been conducted with
oncological patients [29,30] and palliative care patients [31,32]. Positive effects like reduction
of anxiety and improvement of wellbeing [29,30] as well as relaxing and calming experiences
were reported [31].
In this study we examined whether vibroacoustic stimulation through a Body Monochord
differs from listening to relaxation music from audio CD concerning the psychophysiological
relaxation response as it is shown by tonic electrodermal activity and salivary cortisol levels in
patients with psychosomatic disorders. As only little research has been conducted on the treat-
ment with a Body Monochord in clinical subjects, this study is part of a larger study, whose
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 2 / 17
design, data collection and analysis, decision to
publish, or preparation of the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.
other research topics deal with qualitative and quantitative interview data on subjective experi-
ence and electrocortical activity of the brain during the exposure to a Body Monochord,
derived from various groups of psychosomatic patients [25,33].
Focusing one’s attention and abstaining from goal-oriented analytical thinking has been
discussed as necessary for experiencing a state of relaxation [34,35]. Additional stimulation by
vibrations in treatment with the Body Monochord possibly induces a stronger focussing of
attention and thus a deeper relaxation state than merely listening to familiar relaxation music.
It was shown that music combined with tactile perception of low frequencies had a stronger
effect on the reduction of blood pressure and on the improvement of wellbeing in depressive
patients than the mere auditory perception of music [36]. The frequency spectrum of the Body
Monochord used in this study also covers the low frequency region, as there are two sets of
three strings which are tuned to the tone pitches of A1 (55 Hz) and D1 (36.7 Hz). Thus, we
expected a stronger reduction of tonic EDA and salivary cortisol levels during the exposure to
the Body Monochord than by listening to CD music.
Methods and Material
Subjects
The sample consisted of 42 patients (26 of which were women) aged between 20 and 76
(M = 48.5, SD = 12.2) with psychosomatic disorders (somatoform disorder: N = 15; adjust-
ment disorder: N = 11; depressive disorder: N = 11; anxiety disorder: N = 5). The patients par-
ticipated in the study during inpatient treatment at the Department for General Internal and
Psychosomatic Medicine at Charite
´—Universita¨tsmedizin Berlin. The study was approved by
the ethics committee of Charite
´–Universita¨tsmedizin in Berlin (application number: EA1-290-
12) and informed consent was obtained from all patients. All patients provided their written
informed consent to participate in this study.
Procedure
Each patient received a 20-minute exposure to a Body Monochord and a 20-minute presenta-
tion of slow consonant relaxation music (panpipe with piano accompaniment), which was
played on an audio CD. The strings of the Body Monochord were tuned in fifths tuning (tone
pitches: D3, A2, D2, with additional A1 and D1 at three strings each), which allowed it to emit a
sound with a manifold overtone spectrum. The Body Monochord was constructed by the man-
ufacturer of musical instruments Bernhard Deutz in Berlin (http://www.deutz-klangwerkstatt.
de; a sound sample is available at http://psychosomatik.charite.de/forschung/koerpererleben_
koerperzentrierte_therapieverfahren/). For clinical reasons (practicability) data acquisition took
place from about 11 a.m. to 12 p.m. Immediately before each exposure the patients were lying
in a quiet resting state for two minutes. Both treatments were presented in succession in ran-
domized order, with a break of about ten minutes in between. While listening to the CD music
patients were also lying on the Body Monochord. The patients received the instruction to close
their eyes and do nothing else aside from listening to the sound of the music. Immediately after
each treatment method two self-rating scales for assessing the subjective experience during the
single treatment exposition and the state of mood after the treatment were presented.
Cortisol Measurement
Saliva cortisol samples were collected directly before the first treatment session (T1), immedi-
ately after the first one (T2) and immediately after the second treatment session (T3), using
Salivette1sampling devices (Sarstedt, Germany). On doing so the patients chewed on a
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 3 / 17
cotton roll for the duration of about two minutes. The samples were immediately chilled on
ice and centrifuged at 2400 x g for 2 minutes at 4˚C. Then the samples were chilled on ice
again and after the procedure of the presentation of the two treatment methods they were fro-
zen in aliquots at -80˚C until assayed. Cortisol levels (nmol/l) were determined using the com-
mercially available immunoassay ELISA-Kit Parameter™Cortisol Assay (R&D Systems, Inc.,
USA). According to the manufacturer the assay sensitivity for the kit was 0.111 nmol/l. Intra-
assay and inter-assay coefficients of variation were 5.4% and 9.3%, respectively.
EDA Measurement
During the whole investigation SCL was recorded continuously exosomatically from the sur-
face of the skin via application of a direct current voltage of 1.5 V, using the portable biofeed-
back device MentalBioScreen K3 (Porta Bio Screen GmbH, Germany). For the measurement
EKG foam electrodes with a carbon push button and adhesive gel pad (43 x 45 mm) were used
(ASF-40C, Bio Protech Asmuth GmbH, Germany). Two electrodes were fixed to the hypothe-
nar site on each palm of both hands, overlapping about 0.5 cm, thus the distance was about 3.5
cm. The subsequent EDA-analysis was conducted for a 1-minute interval during the resting
position before the treatments and for 1 minute intervals during the periods of 0–1, 5–6, 11–
12 and 17–18 minutes following the start of the Body Monochord and CD music exposure.
The SCL values were averaged for each time interval.
Subjective Experience
As described in detail previously [25], the subjective experiences that occurred during the
exposure to the Body Monochord and the exposure to the CD music were immediately
recorded after the presentation of each treatment method by means of a self rating scale
(7-point Likert scale). The questions were based on the dimensions of experience of the Phe-
nomenology of Consciousness Inventory (PCI) by Pekala [37], German version by Rux [38], a
questionnaire for assessing altered states of consciousness, which can arise e.g. during relaxa-
tion states [39]. For assessing the positive emotional feelings during the two treatments,
patients were asked about feelings of joy, feelings of kindness and the feeling of safety that
occurred during the treatment methods. For each subject the mean value of these categories
was calculated separately for each treatment method. Since negative feelings like fear, anger,
sadness showed rather low values and differed only very slightly between patients, categories
of emotionally negative response were not included in this assessment [25].
Additionally, the Berlin Mood Questionnaire (Berlin Mood Scale, BMS) [40] was carried
out at three points of cortisol measurement (T1, T2, T3). The 30-item BMS measures six differ-
ent states of mood (listlessness, tiredness, anxious depression, anger, involvement, elevated
mood). The items are presented on a 5-point Likert scale.
Statistical Analysis
Statistical data analysis was performed using the statistical software SPSS (Version 20). We
tested the possible effects of the chronological order of the single treatment methods and the
kind of treatment on positive emotional feelings. We did so by calculating an ANOVA with
repeated measurement of the within-subject factor ‘kind of treatment’ (Body Monochord, CD
music) and the between-subject factor ‘treatment chronological order’ (Body Monochord first,
CD music first). Differences in the various dimensions of the BMS in depending of the differ-
ent treatment conditions (T1, T2, and T3) were tested by calculating t-tests for dependent
samples.
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 4 / 17
The possible influences of the chronological order and the kind of the treatments on the
SCL were tested by calculating an ANOVA with repeated measurement of the factor ‘kind of
treatment’ (Body Monochord, CD music) and ‘point in time of measurement’ (Rest, 0–1 min,
5-6- min, 11–12 min, 17–18 min) and the between-subject factor ‘treatment chronological
order‘(Body Monochord first, CD music first).
For statistical analysis of the Cortisol data an ANOVA with repeated measurement of the
factor ‘time of measurement’ (before 1
st
treatment, after 1
st
treatment, after 2
nd
treatment) and
the between-subject factor ‘treatment chronological order’ (Body Monochord first, CD music
first) was calculated. The specifications for alpha error of variance analytical significance test
were based on the Greenhouse-Geisser-adjusted degrees of freedom. Multiple comparisons in
t-tests were adjusted using the Bonferroni-method or Bonferroni-Holm-method, when more
than three comparisons were conducted. Effect sizes were indicated with the coefficients Par-
tial Eta Squared (η
2
) and Cohen’s d.
Results
Six patients were excluded from the statistical analysis of the salivary cortisol data, because
their measurement values of salivary cortisol were outside the standard curve. One patient was
excluded from the statistical analysis of the self-rating scale and five patients were excluded
from the statistical analysis of the BMS because of missing measurement data. SCL data of
eight patients could not be used for statistical analysis because of measurement errors due to
heavy perspiration and low adherence of the electrodes.
Subjective Experience
Results revealed a significant interaction ‘kind of treatment x treatment chronological order’
(F[1,39] = 4.33; p = .044; η
2
= .100). Thus, the treatment method, which was chronologically
presented first, was emotionally experienced in a significantly more positive way than the sec-
ond treatment (Fig 1). The factor ‘kind of treatment’ did not differ significantly in the positive
emotional feelings during Body Monochord and CD music exposure.
The statistical analysis of the BMS showed a significant increase of elevated mood (Body
Monochord: t = -4.53; df = 36; p = .00062; Cohen’s d = -.76; CD music: t = -4.64; p = .00068;
Fig 1. Positive emotional feelings. Mean values of the positive emotional feelings (feelings of joy, feelings of kindness and the
feeling of safety) during the treatments with the Body Monochord (BM) and CD-music in context of the chronological order of the
presentation.
doi:10.1371/journal.pone.0170411.g001
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 5 / 17
Cohen’s d = -.73; Bonferroni-Holm adjusted) and significant reductions of listlessness (Body
Monochord: t = 2.95; df = 36; p = .034, cohen’s d = .48; CD music: t = 2.97; p = .037; df = 36;
Cohen’s d = .49), anger (Body Monochord: t = 3.53; df = 36; p = .009; cohen’s d = .59; CD
music: t = 2.78; df = 36; p = .045; Cohen’s d = .46), and anxious depression (Body Monochord:
t = 5.75; df = 36; p = .000025; Cohen’s d = .96; CD music: t = 4.85; df = 36; p = .00026; Cohen’s
d = .82), both after the exposure to the Body Monochord and after the exposure to the CD
music. All significance values were Bonferroni-holm adjusted. No significant differences were
found between the two kinds of treatment (Fig 2).
Salivary Cortisol
After the presentation of the chronologically first treatment an increase in salivary cortisol
level could be observed both for the Body Monochord and the CD music condition, which
slightly decreased after the second treatment presentation (Fig 3). The factor ‘time of measure-
ment’ (before 1st treatment, after 1st treatment, after 2nd treatment) was significant (F[2,68] =
3.332; p = .051; η
2
= .089). The direct comparison of the mean values between the three points
of measurement revealed that the increase of the salivary cortisol level from the first to the sec-
ond point of measurement is significant (t = -2.688; df = 35; p = .033, Cohen’s d = .24; Bonfer-
roni-adjusted). The difference of salivary cortisol between the first and the third point of
measurement missed the significance level (t = -1.404; df = 35; p = .169, Cohen’s d = .15), as
well as the difference between the second and the third point of measurement (t = 1.156;
df = 35; p = .256, Cohen’s d = .07).
The between subject factor ‘treatment chronological order’ did not show any significance,
which means that the cortisol levels did not differ significantly between the patients, who were
presented the two treatment conditions in chronological different order.
The interaction ‘time of measurement x treatment chronological order’ was also not signifi-
cant, revealing that chronological course of the cortisol levels did not differ significantly in
dependence of chronological order of the treatment presentation. Thus the two treatment
methods Body Monochord and the exposure to CD music did not differ significantly in their
Fig 2. Berlin Mood Questionnaire (BSF). Perceived states of mood measured via the Berlin Mood Questionnaire (BSF) at the
resting condition, after the exposure to the Body Monochord, and after the exposure to the CD music. (N = 37).
doi:10.1371/journal.pone.0170411.g002
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 6 / 17
influence on the secretion of cortisol. As well, the direct comparison of the mean values
between Body Monochord and CD music did not show any significance.
As the increase in cortisol levels was contradictory to our expectations, we explored possible
artefacts. For all patients the last medication and food intake took place between 8 a.m. and
8.30 a.m., about 3 hours before the psychophysiological measurements. Six patients did not
take any medication at all, whereas thirty patients took one or more medicaments of the medi-
cation listed in Table 1. As cortisol belongs to the class of glucocorticoids, the intake of gluco-
corticoids might have influenced the cortisol system. The other drug agents listed in the table
are not known to significantly influence cortisol levels. Furthermore, it has been shown that
underweight and obesity have various influences on patients’ cortisol levels and responsiveness
of the cortisol system [41,42]. For that reaseon we repeated the calculation of the compared t-
test without those patients, who had taken glucocorticoids (N = 5) and those patients with a
BMI over 30 (N = 5) or below 18 (N = 3), so that altogether 13 patients were excluded. The
results of the new calculation confirmed the previous findings and revealed even a higher effect
size for the increase in salivary cortisol levels from the first to the second point of measurement
(t = -2.58; df = 22; p = .051, Cohens d = .36, Bonferroni-adjusted). The differences in salivary
cortisol between the first and the third and between the second and the third point of measure-
ment again missed the significance level.
EDA-Activity (SCL)
During both treatment methods a pronounced decrease of SCL was observed (Fig 4). The factor
‘point in time of measurement’ was highly significant (F[4,128] = 31.59; p <.001; η
2
= .497) and
showed a highly significant linear trend (F[1,32] = 42.38; p <.001; η
2
= .570. The factor ‘kind of
treatment’ was not significant. These results indicate that the decrease of SCL during the two
treatment methods was significant over time and did not differ significantly between the two
treatment methods. We found a highly significant interaction effect between ‘kind of treatment’
and ‘treatment chronological order’ (F[1,32] = 15.15; p <.001; η
2
= .321). This indicates that
Fig 3. Salivary cortisol. Salivary cortisol levels measured immediately before the first treatment after the resting condition,
immediately after the first treatment and after the second treatment for the two groups with different chronological order of the two
kinds of treatment (N = 36).
doi:10.1371/journal.pone.0170411.g003
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 7 / 17
during the treatment method, which was presented first, there was a greater reduction of SCL
compared to the treatment method, which was presented in the second place.
The interaction ‘kind of treatment x treatment chronological order x point in time of mea-
surements” reached only the 10% alpha error level (F[4,128] = 2.98; p = .067; η
2
= .085), but
shows the tendency for difference between the two treatment methods in the course of SCL
over time dependent of the chronological order of presentation. Thus, we calculated the mean
values of the last three measurement points (5–6, 11–12 and 17–18 min, following the start of
the treatments) separately for each treatment presentation and performed paired t-tests to
check the significance of the differences between the treatment method that was presented
first and the treatment method that was presented second. Results revealed that during the
treatments presented first, there were higher decreases in SCL than during the treatments pre-
sented second, which only just missed the significance level of 5% (Body Monochord pre-
sented first: t = 2.34; df = 20, p = .060, cohen’s d = .45, Bonferroni-adjusted; CD music
presented first: t = 2.43; df = 16; p = .054, cohen’s d = .63, Bonferroni-adjusted).
Discussion
In this study we examined the effects of vibroacoustic stimulation via a Body Monochord in
comparison with a relaxation music CD on the skin conductance level (SCL) and salivary
Table 1. Medication, taken by the patients about 3 hours before physiological measurements.
Drug class Agent
Antidepressant Citalopram, Sertralin, Duloxetin, Amitriptylin, Trimipramin, Opipramol, Bupropion, Mirtazapin, Hypericum
perforatum
Antiepileptic Gabapentin
Neuroleptic Olzapin, Pipamperon
Sedative Zoplicon
Antidiabetic Metformin
Cholesterol reducer Simvastatin, Ezetimib
Antihistamine Mizolastin, Fexofenadin, Dimetinden, Betahistin
Proton pump inhibitor Omeprazol, Pantoprazol, Lansoprazol
Alpha-blocker Doxazosin, Tamsulosin
ACE inhibitor Enalapril, Ramipril, Lisinopril
Beta-blocker Metoprolol, Bisoprolol
AT1-antagonist Candesartan, Olmesartan, Telmisartan
Calcium channel blocker Amlodipin, Lercanidipin
Non-steroidal antirheumatic/non-opioid
analgetic
Diclofenac, Acetylsalicylic acid, Metamizol, Flupirtin, Paracetamol, Ibuprofen
Glucocorticoid Fluticason, Triamcinolon, Methylprednisolon, Budesonid, Ciclesonid
Vitamin Thiamin (Vitamin B1), Colecalciferol (Vitamin D)
Mineral Magnesium, Kaliumiodid, Dinatriumhydrogenphosphat, Kalium dihydrogenphosphat, Calcium carbonat,
Diuretic Hydrochlorothiazid, Torasemid
Immunosuppressant Everolimus, Mycophenolat
Sex hormon Estradiol
Thyroid hormone Levothyroxin
Spasmolytic Darinefacin
Dopamine agonist Pramipexol
Antiemetic Metoclopramid
Thrombocyte aggregation inhibitor Clopidogrel
Beta-sympathomimetic Salbutamol
doi:10.1371/journal.pone.0170411.t001
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 8 / 17
cortisol levels in patients with psychosomatic disorders, in relation to the emotional evaluating
scores for subjective experience during the exposure to the treatments.
Subjective Experience
As a sequence effect we found that the treatment mode presented first was scored in an emo-
tionally more positive way (respectively, feeling of kindness, feeling of safety, and feeling of
joy) than the treatment mode presented in the second place, a result which corresponds to the
findings of a larger sample without cortisol measurements [25]. This may be explained by the
duration of the examination, taking about two hours altogether, which might have reduced
patients’ willingness to get involved in the second treatment. Furthermore, both the exposure
to the Body Monochord and the exposure to the CD music induced an improvement of
patients’ scores for state of mood, namely an increase in elevated mood and a decrease in anx-
ious depressiveness, anger and listlessness.
Salivary Cortisol
Both after the presentation of the first and the second treatment session, an increase in salivary
cortisol was observed both for the exposure to the Body Monochord and the exposure to the
CD music. The results revealed that the increases from the initial resting period to the points
of measurement immediately after the first treatment exposure were significant. The treatment
with the Body Monochord and the treatment with the CD music did not differ significantly in
their influence on the secretion of cortisol. In visual terms, the group of patients, who had
been presented the CD music at first, showed lower levels of cortisol at all the three measure-
ment points, but these differences did not show any significance. The lack of significance can
be explained by the high standard deviations of the measurement values. For the same reason
Fig 4. Electrodermal activity (SCL). Course of SCL during the two kinds of treatment (Body Monochord, CD music). The left
diagram shows the courses of the SCL when the Body Monochord was presented as first and the CD music was presented as second
exposure. The right diagram shows the courses of the SCL when the CD music was presented as first and the Body Monochord was
presented as second exposure.
doi:10.1371/journal.pone.0170411.g004
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 9 / 17
the increase between the first and second measurement points was significant and the increase
between the first and the third measurement points was not.
The increase of salivary cortisol levels during the two treatments with the Body Monochord
and the CD music is contrary to our expectations that listening to music, especially to relaxa-
tion music, and experiencing relaxation states are associated with a decrease in cortisol levels,
as revealed in former studies [17–19,21–23,43,44]. After the first treatment session, which
was experienced in an emotionally more positive way, the increase in salivary cortisol was sig-
nificant and more pronounced than after the second presentation of the treatment session,
which was emotionally experienced in a slightly less positive way.
Regarding research on the relation between emotion, affect and cortisol, an increase in cor-
tisol levels is in general associated with negative affect. On the other hand, positive affect is
rather associated with a decrease in cortisol levels [45–47]. Other studies revealed that there
was no effect of positive daily events on cortisol levels [48]. Furthermore, it was shown that
positive emotion with high physiological arousal, in terms of being alert and active, was associ-
ated with a decrease in salivary cortisol [49]. On the other hand, positive emotion with low
physiological arousal, in terms of being happy and relaxed, did not show any effects on cortisol
levels.
Thus, our results seem to contradict findings of studies, which revealed that negative, but
not positive affect is associated with higher cortisol levels. Another investigation of our work-
ing group, which compared the effects of the Body Monochord in the shape of a chair and in
the shape of a lounger, found similar results concerning the increase of salivary cortisol levels
in patients suffering from eating disorders, somatoform disorders and pain disorders [50].
This makes it unlikely that the reported increase in salivary cortisol is based on measurement
errors.
It might be possible that the relaxation states, induced by listening to the relaxation music
and by vibroacoustic stimulation, in some patients also constituted a kind of emotional chal-
lenge related to stress, which might be reflected in the increase of cortisol levels. Relaxation
techniques, which use imagery, are supposed to be more likely to induce adverse experiences
than relaxation techniques without imagery, because intrusive distressing images and thoughts
might be enhanced more easily through imagery instructions, which would lead to an increase
in arousal [51]. In general, during relaxation states unconscious or preconscious contents,
which might be related to conflicts in one’s personal life, are more likely to appear [52]. The
appearance of these phenomena is used in the psychotherapeutic technique e.g. of Guided
Imagery and Music [53].
The analysis of qualitative interview data on subjective experiences during the treatment
with a Body Monochord of patients suffering from eating disorders [54] revealed that chang-
ing inner images, thoughts, body-related feelings and emotions occurred during the course of
the treatment, which also means that short phases of pleasant and unpleasant experiences
sometimes alternated. Possibly, similar subjective experiences during the treatment with the
Body Monochord and CD music might have occurred in the patients we investigated in this
study.
Previous studies on the impact of music or relaxation on cortisol levels mainly investigated
healthy subjects who were not suffering from psychological disorders [22,23,43,55]. As the
patients in our study were suffering from depressive disorders, anxiety disorders, adjustment
disorders and somatoform disorders, which are supposed to be associated with individual psy-
chosocial stress factors, part of these stress factors might have come to consciousness by focus-
ing the attention towards the self by means of the vibroacoustic stimulation and listening to
the sound and music. Taken as a whole, aside from pleasant and relaxing phases of subjective
experiences during the treatment sessions, the treatments by themselves might have been
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 10 / 17
emotionally challenging experiences, which could be the reason for the increase of patients’
salivary cortisol levels.
The former results of the analysis of the electrocortical activity (EEG) during the treatment
with the Body Monochord in a larger sample [33] might give a hint to a possible mental stress
processing in the beginning of the treatment. During the first minutes of exposure to the Body
Monochord a desynchronsation both of the EEG-Theta and Alpha bands occurred (see results
in [33]). As described in detail previously [33], desynchronised EEG-Alpha activity is an indi-
cator of increased attention during the expectation of cognitive tasks and information process-
ing [56,57]. Synchronised Theta activity is associated with relaxation [58] (and correlates with
focused attention and memory search [59–61]. Due to the fact that both the Alpha and the
Theta bands are desynchronisized, this result suggests that in the beginning of the exposure to
the Body Monochord a state of increased vigilance took place without any mental relaxation,
memory processing or focused attention. The desynchronization of the EEG could thus be
matched with a situation of mental orientation in which an attempt is made to make sense of
and to structure the unusual perception, which might also be interpreted as stress processing.
It should be mentioned that during the exposure to the CD music these EEG effects were not
observed.
Skin Conductance Level
The increase in salivary cortisol as an indicator of a stress response seems to be contradicted
by the decrease in the SCL, which indicates an experience of relaxation. During the first treat-
ment the decrease in SCL was significantly more pronounced than during the second treat-
ment. This result corresponds with the sequence effect of positive emotional feelings, which
were scored as being higher during the first treatment compared to the second treatment. This
is consistent with results of former studies, which demonstrated an association between feel-
ings of relaxation, wellbeing or contentment and a reduction of SCL [14].
As we discuss the increase in salivary cortisol levels as a possible indicator of a stress
response that occurred during the treatment sessions, and as the SCL is regarded to be an indi-
cator of emotion-associated sympathetic activity, one would expect an increase in SCL during
an emotionally challenging experience. But the emotionally associated SCL response is proba-
bly masked over by a possible relaxation response, which is induced by focussing on the music
or by just lying on the lounger. In a study by Nater and colleagues [62] on psychophysiological
and emotional responses to musical stimuli, listening to Heavy Metal music led to an increase
in unrest and aggression, whereas smoothing classical music led to more calmness and im-
provement of mood. The SCL levels were higher during listening to Heyvy Metal music, but
both during the Heavy Metal music and the relaxing music a decrease in the courses of SCL
could be observed. However, these contradictory results were not discussed in this article,
because the focus of the study was on different responses of men and women to musical sti-
muli. Possibly the focussing on the music in a resting position facilitated a physical relaxation
state, which at the same time was masked by the emotional arousal because of the music. Thus,
on the one hand during listening to Heavy Metal music the SCL was higher than during relaxa-
tion music, but on the other hand the SCL decreased during both conditions probably due to
physical relaxation.
It should also be noted that in our study on the effects of the Body Monochord and relaxa-
tion music on psychophysical parameters and subjective experience we altogether examined
101 patients (of which only 42 were measurd by salivary cortisol) of which 8 patients discon-
tinued the treatments because of unpleasant feelings or imageries that occurred (Body Mono-
chord: N = 7, CD music: N = 1). Fig 5 shows the courses of SCL until the termination of the
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 11 / 17
treatment. It is striking that 6 patients showed an obvious decrease in SCL, whereas in 2 patients
the SCL remained about the same level. These results give hint to the existence of a kind of para-
doxical relaxation response, in which the electrodermal activity decreases, whereas unpleasant
or stressfull feelings or imageries are processed mentally. The physical position of resting and
lying down probably facilitates the relaxation of the skeletal muscles. The patients were invited
to do nothing else but paying attention to the sound and music. Focusing of attention without
distraction combined with a relaxing position of the body is supposed to be necessary to
encourage the appearance of a relaxation response, as described in the literature [34,35].
However, the question arises why the increase in cortisol was not masked by the same effect.
Possibly the electrodermal activity and the activation of the HPA-axis represent independent
components concerning the relaxation response. This could mean that the decrease in SCL
might be more strongly influenced by the physical calming effect whereas the increase in sali-
vary cortisol levels might be more associated with inner mental activity and might be less sensi-
tive to mere physical rest. A study of Pawlow and Jones [63] showed that merely sitting quietly
did not show any impact on salivary cortisol levels.
However, the exposure both to the Body Monochord and to the relaxation music led to an
increase in elevated mood and a decrease in anxious depressiveness, anger and listlessness
(dimensions of the BMS–Berlin Mood Scale). It should be noted that the self-rating of the
BMS refers to the state of mood that patients experienced at the point in time immediately
after the treatment exposure. Probably the state of mood did not remain the same during the
whole exposure. Presumably, during the exposure to the Body Monochord and maybe also
during the CD music changing contents of mental images, thoughts and memories ocurrued
and both pleasant and unpleasant states of mood might have appeared alternately, similar to
the patients suffering from eating disorders, whose subjective experience during Body Mono-
chord treatements was investigated in another study of our working group [54]. The viewing
of the qualitative interview data of patients in the present study and of the whole sample
Fig 5. Electrodermal activity (SCL) of the patients who discontinued the treatment session. Individual courses of the SCL of
the patients who discontinued the treatment session with the Body Monochord (N = 7) or the CD music (N = 1) because of unpleasant
feelings or occurring imageries. The last measurement points refer to the last minute immediately before termination of the treatment
exposure.
doi:10.1371/journal.pone.0170411.g005
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 12 / 17
suggests that part of the patients indeed experienced the treatment as emotionally challenging,
especially in the beginning. This happened because unpleasant memories or actual problems
in life emerged in their minds, from which, however, they could distance themselves in the fur-
ther course of the treatment exposure [64]. Thus, the rated mood at the point in time after the
treatment exposure might be the result of coming to terms with a somehow challenging emo-
tional process.
Another explanation for the increase in salivary cortisol might be the possibility that the
patients’ experiences of elevated mood and decrease in listlessness also indicated an activating
process, induced both by the bodily vibroacoustic stimulation and the inner images, which
might have been encouraged through sound and music. So this activating process might have
been experienced as a kind of eustress, which might have caused the increase of salivary corti-
sol levels.
Limitations
The cortisol results must be interpreted with caution, because it cannot be completely excluded
that the release of cortisol was influenced by a variety of drugs like beta-blocker propanol, anti-
depressants or others, which were taken by various patients prior to testing. Possibly the medi-
cation caused a delayed onset of the cortisol release and led to the rise in cortisol observed over
the treatment.
Another limitation regarding cortisol might be the fact, that the release of cortisol follows a
circadian rhythm, which culminates in the morning after waking up and decreases throughout
the rest of the day [65,66]. The patients had been tested during the late morning when higher
fluctuations in cortisol levels can be assumed. To address this problem and to reduce possible
influences of medication, further studies should be conducted in the late afternoon.
As the focus of this study was on the impact of vibroacoustic stimulation on patients’
salivary cortisol levels and electrodermal activity in relation to their subjective emotional
experience, we did not include a control group with healthy subjects. Thus the study has an
explorative character and the absence of a control group can be considered as a limitation.
Furthermore, it can be regarded as a limitation that we did not include more direct psycho-
logical measures of relaxation and stress e.g. like visual analogue scales, because the focus of
the study was on the patient’s state of mood and emotional experience. This could have pro-
vided additional information about the perceived state induced by the treatments.
A further limitation of the study is the fact that there was only a break of ten minutes
between the successive interventions. This might have been not enough time for the physiolog-
ical systems to return to a true baseline. One way of avoiding this problem is to perform the
measurements on two different days. But it must be taken into consideration that on different
days usually different unavoidable therapeutic and diagnostic procedures are conducted due
to the clinical context, which might have been experienced as different additional stress factors.
In this context our study has an explorative character, which should invite to further studies.
Finally, it can be taken into consideration whether the cortisol system of patients might be
dysregulated to varying degrees due to long lasting distress, which finally led to disease and
inpatient admission. Moreover, it is to be assumed that patients had different lengths of time
for recovery, because of different length of hospital stay or different influencing factors which
might have occurred during the stay in hospital before the investigation. This might have some
impact on possible differences between the responsiveness of the cortisol system and the elec-
trodermal activity to pleasing or displeasing stimuli. In order to address this issue, it would be
necessary to investigate several treatments in single persons over a longer period of time by
means of time series analysis.
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 13 / 17
Conclusion
A relaxation state, induced by vibroacoustic stimulation or listening to CD music, is associated
with a reduction of the electrodermal activity and thus of the sympathetic arousal, which was
more pronounced during higher emotionally positive feelings during the treatments.
Both vibroacoustic stimulation and listening to relaxation music induced an improvement
of patients’ mood and were associated with an increase in salivary cortisol. The increase in sali-
vary cortisol might be explained by a potentially challenging experience of the relaxation state
due to possibly uncommon body sensations and inner images. Thus the electrodermal activity
and the HPA-axis might be independent components concerning the relaxation response,
which could mean that the decrease in tonic electrodermal activity might better reflect the
physical calming effect and the increase in salivary cortisol levels might be more associated
with inner mental activity.
Supporting Information
S1 File. Patients’ data. The data file contains patients’ data of Sex, Age, Salivary Cortisol, Elec-
trodermal Activity (SCL), Positive Emotional Feelings and Berlin Mood Scale (BMS).
(XLS)
S2 File. SCL of dropouts. Electrodermal Activity (SCL) of patients, who discontinued the
treatment exposure.
(XLS)
Author Contributions
Conceptualization: HS BFK RB UF.
Data curation: HS PB.
Formal analysis: HS PB.
Funding acquisition: BFK.
Investigation: HS BFK RB UF.
Methodology: HS BFK RB UF.
Project administration: BFK MR.
Resources: BFK RB.
Supervision: BFK RB MR.
Validation: HS PB.
Visualization: HS.
Writing – original draft: HS.
Writing – review & editing: BFK RB UF.
References
1. Bradt J., Dileo C. Music for stress and anxiety reduction in coronary heart disease patients. Cochrane
Database Systematic Review: 2009; 12:CD006577.
2. Bradt J., Dileo C., Grocke D., Magill L. Music interventions for improving psychological and physical out-
comes in cancer patients. Cochrane Database Systematic Review. 2011; 8:CD006911.
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 14 / 17
3. Chan M F, Chung YF, Chung S W, Lee OK. Investigating the physiological responses of patients listen-
ing to music in the intensive care unit. Journal of Clinical Nursing. 2009; 18(9),1250–1257 doi: 10.1111/
j.1365-2702.2008.02491.x PMID: 18775053
4. Chlan LL. Music therapy as a nursing intervention for patients supported by mechanical ventilation.
Complementary and alternative therapies. American Association of Critical–Care Nurses. 2000; 11,
128–138
5. Han L, Li JP, Sit JW, Chung L, Jiao ZY, Ma WG. Effects of music intervention on physiological stress
response and anxiety level of mechanically ventilated patients in China: a randomised controlled trial.
Journal of Clinical Nursing. 2010; 19(7–8), 978–987 doi: 10.1111/j.1365-2702.2009.02845.x PMID:
20492042
6. Lee OKA, Chung YFL, Chan MF, Chan WM. Music and its effect on the physiological responses and
anxiety levels of patients receiving mechanical ventilation: a pilot study. Journal of Clinical Nursing.
2005; 14, 609–620 doi: 10.1111/j.1365-2702.2004.01103.x PMID: 15840076
7. Weeks BP, Nilsson U. Music inteventions in patients during coronary angiographic procedures: A rand-
mized controled study of the effect on patients’ anxiety and well-being. European Journal of Cardiovas-
cular Nursing. 2011; 10, 88–93 doi: 10.1016/j.ejcnurse.2010.07.002 PMID: 20685168
8. White JM. Effects of relaxation music on cardiac autonomic balance and anxiety after myocardial infarc-
tion. American Journal of Critical Care. 1999; 8 (4), 220–230 PMID: 10392221
9. Bernardi L, Porta C, Sleight P. Cardiovascular, cerebrovascular, and respiratory changes induced by
different types of music in musicans and non-musicans: the importance of silence. Heart. 2006; 92,
445–452 doi: 10.1136/hrt.2005.064600 PMID: 16199412
10. Labbe
´E, Schmidt N, Barbin J, Pharr M. Coping with stress: the effectiveness of different types of music.
Journal of Applied Psychophysiology and Biofeedback. 2007; 32 (3), 163–168
11. Sandstrom GM, Russo FA. Music hath charms: the effects of valence and arousal on recovery following
an acute stressor. Music and Medicine. 2010; 2, 137–143
12. Yamamoto M, Naga S, Shimizu J. Positive musical effects on two types of negative stressful conditions.
Psychology of Music. 2007; 35 (2), 249–275
13. Boucsein W. Electrodermal Activity. Second Edition. Springer: New York. 2007
14. Kreibig SD. Autonomic nervous system activity in emotion: A review. Biological Psychology. 2010; 84,
394–421 doi: 10.1016/j.biopsycho.2010.03.010 PMID: 20371374
15. Castro M, Elias PCL, Martinelli JR, Antonini SRR, Santiago L, Moreira AC. Salivary Cortisol as a tool for
physiological studies and diagnostic strategies. Brazilian Journal of Medical and Biological Research.
2000; 33(10), 1171–1175 PMID: 11004717
16. Hellhammer D, Wu¨st S, Kudielka B. Salivary cortisol as a biomarker in stress research. Psychoneuroen-
docrinology. 2009; 34, 163–171 doi: 10.1016/j.psyneuen.2008.10.026 PMID: 19095358
17. Jevning R, Wilson AF, Davidson JM. Adrenocortical activity during meditation. Hormones and Behavior.
1978; 10, 54–60 PMID: 350747
18. Jin P. Changes in heart rate, noradrenaline, cortisol and mood during Tai Chi. Journal of Psychosomatic
Research. 1989; 33(2), 197–206 PMID: 2724196
19. Lee MS, Kang C-W, Lim H-J, Myung-Suk Lee M-S. Effects of Qi-training on anxiety and plasma concen-
trations of cortisol, ACTH, and aldosterone: a randomized placebo-controlled pilot study. Stress and
Health. 2004; 20, 243–248
20. Pawlow LA, Jones GE. The impact of abbreviated progressive muscle relaxation on salivary cortisol
and salivary immunoglobulin A (sIgA). Applied Psychophysiology and Biofeedback. 2005; 30 (4), 375–
387 doi: 10.1007/s10484-005-8423-2 PMID: 16385425
21. Sudsuang R, Chentanez V, Veluvan K. Effect of Buddhist meditation on serum cortisol and total protein
levels, blood pressure, pulse rate, lung volume and reaction time. Physiology and Behavior. 1991; 50
(3), 543–548 PMID: 1801007
22. Mo
¨ckel M, Ro
¨cker L, Sto
¨rk T, Vollert J, Danne O, Eichsta
¨dt H, et al.Immediate physiological responses
of healthy volunteers to different types of music: cardiovascular, hormonal and mental changes. Euro-
pean Journal of Applied Physiology and Occupational Physiology. 1994; 68, 451–459 PMID: 7826431
23. Koelsch S, Fuermetz J, Sack U, Bauer K, Hohenadel M, Wiegel M, et al. Effects of music listening on
cortisol levels and propofol consumption during spinal anesthesia. Frontiers in Psychology. 2011; 2,
58, 1–9
24. Uedo N., Ishikawa H., Morimoto K., Ishihara R., Narahara H., Akedo I., et al. Reduction in salivary corti-
sol level by music therapy during colonoscopic examination. Hepatogastroenterology. 2004; 52(56),
451–453
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 15 / 17
25. Sandler H, Fendel U, Peters E, Rose M, Bo
¨sel R, Klapp BF. Subjective experience of relaxation—
induced by vibroacoustic stimulation by a Body Monochord or CD music–a randomised, controlled
study in patients with psychosomatic disorders. Nordic Journal of Music Therapy. 2015;
26. Harthog T. The reception of monotonal sounds. An empirical study of the perception of monochords.
Zeitschrift fu¨r Musik-, Tanz- und Kunsttherapie. 2001; 12(3), 111–19
27. Jungaberle H, Altieri P, Gerloff E, Kurze K, Verres R. Sounds streaming in–Contribution to the music
psychology of monochords. Musiktherapeutische Umschau. 2003; 24, 319–32
28. Sandler H, Tamm S, Klapp B, Bo
¨sel R. The body monochord–Effects on EEG and subjective experi-
ence. Zeitschrift fu¨r Musik-, Tanz- und Kunsttherapie. 2008; 19(3), 110–20
29. Lee E-J, Bhattacharya J, Sohn C, Verres R. Monochord sounds and progressive muscle relaxation
reduce anxiety and improve relaxation during chemotherapy: a pilot study. Complementary Therapies
in Medicine. 2012; 20, 409–416 doi: 10.1016/j.ctim.2012.07.002 PMID: 23131371
30. Rose J-P, Weis J. Sound meditation in oncological rehabilitation–a pilot study of a receptivem usic ther-
apy group using the monochord. Forschende Komplementa
¨rmedizin. 2008; 16(6), 335–43
31. Teut M, Dietrich C, Deutz B, Mittring N, Witt CM. Perceived outcomes of music therapy with Body Tam-
bura in end of life care—a qualitative pilot study. BMC Palliative Care. 2014; 13(1), 18 doi: 10.1186/
1472-684X-13-18 PMID: 24708801
32. Warth M, Kessler J, Kotz S, Hillecke TK, Bardenheuer HJ. Effects of vibroacoustic stimulation in music
therapy for palliative care patients: a feasibility study. BMC Complementary and Alternative Medicine.
2015; 15:436 doi: 10.1186/s12906-015-0933-8 PMID: 26669437
33. Sandler H, Tamm S, Fendel U, Rose M, Klapp BF, Bo
¨sel R. Positive emotional experience–induced by
vibroacoustic stimulation using a Body Monochord in patients with psychosomatic disorders–is associ-
ated with an increase in EEG-theta and a decrease in EEG-alpha power. Brain Topography. 2016;
34. Benson H, Beary JF, Carol MP. The relaxation response. Psychiatry. 1974; 37. 37–46
35. Smith JC, Amutio S, Anderosn JP, Aria LA. Relaxation: Mapping an uncharted world. Biofeedback and
Self-Regulation. 1996; 21(1), 63–90 PMID: 8833317
36. Spitzer M, Rath F, Groen G. Music and subjective well being–prelimanary results on use of a sound bed
in depressive patients. Nervenheilkunde. 2005; 3, 198–202
37. Pekala RJ. Quantifying Consciousness: An Empirical Approach. New York Plenum Press. 1991
38. Rux M. Erprobung der deutschen U
¨bersetzung des Phenomenology of Consciousness Inventory von
Pekala: Normwerte, Gu¨tekriterien, A
¨nderungsvorschla
¨ge. Universita
¨t Gießen. 2002
39. Vaitl D, Gruzelier J, Jamieson GA, Lehmann D, Ott U, Sammer G, et al. Psychobiology of Altered States
of Consciousness. Psychological Bulletin. 2005; 131(1), 98–127 doi: 10.1037/0033-2909.131.1.98
PMID: 15631555
40. Ho
¨rhold M, Klapp BF, Schimmack U. Testing the invariance and hierarchy of a multidimensional model
of mood by means of repeated measurement with student and patient sample. Zeitschfrift fu¨r medizi-
nische Psychologie. 1993; 1, 27–35
41. Incollingo Rodriguez AC, White ML, Standen EC, Seckl JR, Tomiyama AJ. Hypothalamic-pituitary-adre-
nal axis dysregulation and cortisol activity in obesity: A systematic review. Psychoneuroendocrinology.
2015; 62, 301–318 doi: 10.1016/j.psyneuen.2015.08.014 PMID: 26356039
42. Putignano P, Dubini A., Toja P, Invitti C, Bonfanti S, Redaelli G, et al. Salivary cortisol measurement in
normal-weight, obese and anorexic women: comparison with plasma cortisol. European Journal of
Endocrinology. 2001; 145, 165–171 PMID: 11454512
43. Khalfa S, Bella SD, Roy M, Peretz I, Lupien SJ. Effects of relaxing music on salivary cortisol level after
psychological stress. Annals New York Academy of Sciences. 2003; 999, 374–376
44. Miluk-Kolasa B, Obminski Z, Stupnicki R, Golec L. Effects of music treatment on salivary cortisol in
patients exposed to pre-surgical stress. Experimental and Clinical Endocrinology. 1994; 102(2), 118–
120 doi: 10.1055/s-0029-1211273 PMID: 8056055
45. Booij SH, Bos EH, de Jonge P, Oldehinkel AJ. The temporal dynamics of cortisoland affective states in
depressedand non-depressed individuals. Psychoneuroendocrinology. 2016; 69, 16–25 doi: 10.1016/j.
psyneuen.2016.03.012 PMID: 27017429
46. Buchanan TW, al’Absi M, Lovallo WR. Cortisol fluctuates with increases and decreases in negative
affect. Psychoneuroendocrinology. 1999; 24, 227–241 PMID: 10101730
47. Smyth J, Ockenfels MC, Porter L, Kirschbaum C, Hellhammer DH, Arthur A, et al. Stressors and mood
measured on a momentary basis are associated with salivary cortisol secretion. Psychoneuroendocri-
nology. 1998; 23 (4), 353–370 PMID: 9695136
48. Peeters F, Nicholson NA, Berkhof J. Cortisol Responses to Daily Events in Major Depressive Disorder.
Psychosomatic Medicine. 2003; 65, 836–841 PMID: 14508029
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 16 / 17
49. Hoyt LT, Craske MG, Mineka S, Emma K, Adam EK. Positive and Negative Affect and Arousal: Cross-
Sectional and Longitudinal Associations With dolescent Cortisol Diurnal Rhythms, Psychosomatic Med-
icine. 2015; 77, 392–401 doi: 10.1097/PSY.0000000000000178 PMID: 25905661
50. Fendel U. et al. Unpublished data in preparation for publication.
51. Harding S. Relaxation: with or without imagery? International Journal of Nursing Practice. 1996; 2(3),
160–162 PMID: 9265611
52. Vaitl D. Autogenes Training. In: Vaitl D. & Petermann F. (Hrsg.). Handbuch der
Entspannungsverfahren, pp. 206–255. Weinheim: Beltz Psychologie Verlags Union. 2000
53. Summer L. Music consciousness: The evolution of guided imagery and music. Gilsum, NH: Barcelona
Publishers. 2002
54. Fendel U. et al. 2017. Publication in process.
55. Gingras B, Pohler B, Fitch WT. Exploring Shamanic Journeying: Repetitive Drumming with Shamanic
Instructions Induces Specific Subjective Experiences but No Larger Cortisol Decrease than Instrumen-
tal Meditation Music. PLOS ONE, 2014; 9(7): e102103. doi: 10.1371/journal.pone.0102103 PMID:
24999623
56. Dujardin K, Derambure P, Defebvre L, Bourriez JL, Jacquesson JM, Guieu JD. Evaluation of event-
related desynchronization (ERD) during a recognition task: effect of attention. Electroencephalography
and Clinical Neurophysiology. 1993; 86(5), 353–56 PMID: 7685270
57. Klimesch W. EEG alpha and theta oscillations reflect cognitive and memory performance: a review and
analysis. Brain Research Reviews 1999; 29(2–3), 169–195 PMID: 10209231
58. Cahn BR, Polich J. Meditation states and traits: EEG, ERP, and neuroimaging studies. Psychological
Bulletin. 2006; 132(2), 180–211 doi: 10.1037/0033-2909.132.2.180 PMID: 16536641
59. Bo
¨sel R. Die cerebrale Theta-Rhythmizita
¨t unterstu¨tzt kontextabha
¨ngige Diskriminationsleistungen.
Kognitionswissenschaft. 1993; 3(1), 53–69
60. Deiber M-P, Missonier P, Bertrand O, Gold G, Fazio-Costa L, Ibanez V. Distinction between perceptual
and attentional processing in working memory tasks: a study of phase-locked and induced oscillatory
brain dynamics. Journal of Cognitive Neuroscience. 2007; 19(1), 158–172 doi: 10.1162/jocn.2007.19.
1.158 PMID: 17214572
61. Pennekamp P, Bo
¨sel R, Mecklinger A, Ott H. Differences in EEG-theta for responded and omitted tar-
gets in a sustained attention task. Journal of Psychophysiology. 1994; 8, 131–41.
62. Nater UM, Abbruzzese E, Krebs M, Ehlert U. Sex differences in emotional and psychophysiological
responses to musical stimuli. International Journal of Psychophysiology. 2006; 62, 300–308 doi: 10.
1016/j.ijpsycho.2006.05.011 PMID: 16828911
63. Pawlow LA, Jones GE. The impact of abbreviated progressive muscle relaxation on salivary cortisol
and salivary immunoglobulin A (sIgA). Applied Psychophysiology and Biofeedback. 2005; 30(4), 375–
387 doi: 10.1007/s10484-005-8423-2 PMID: 16385425
64. Sandler et al. Unpublished data in preparation for publication.
65. Krieger DT, Allen W, Rizzo F, Krieger HP. Characterization of the normal temporal pattern of plasma
corticosteroid levels. Journal of Clinical Endocrinology and Metabolism. 1971; 32(2), 266–284 doi: 10.
1210/jcem-32-2-266 PMID: 4321505
66. Weitzman ED, Fukushima D, Nogeire C, Roffwarg H, Gallagher TF, Hellman L. Twenty-four hour pat-
tern of the episodic secretion of cortisol in normal subjects. Journal of Clinical Endocrinology and Metab-
olism. 1971; 33(1), 14–22 doi: 10.1210/jcem-33-1-14 PMID: 4326799
Relaxation - Effects on Electrodermal Activity and Cortisol Levels in Psychosomatic Patients
PLOS ONE | DOI:10.1371/journal.pone.0170411 January 23, 2017 17 / 17
