Complementary Therapies in Clinical Practice 21 (2015) 193e200

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Complementary Therapies in Clinical Practicejournal homepage: www.elsevier.com/locate/ctcp

Acupuncture-induced changes of vagal function in patients withdepression: A preliminary sham-controlled study with press needles
Yoshihiro Noda a, b, c, Takuji Izuno a, Yoshie Tsuchiya a, Shunsuke Hayasaka a,
Kiiko Matsumoto d, Hirohiko Murakami a, Arata Ito a, Yukari Shinse a, Aya Suzuki a,Motoaki Nakamura a, *aKanagawa Psychiatric Center, 2-5-1 Serigaya, Kohnan-ku, Yokohama, Kanagawa, 233-0006, Japan
Department of Neuropsychiatry, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
Centre for Addiction and Mental Health, Department of Psychiatry, University of Toronto, 1001 Queen Street West, Toronto, ON, M6J 1H4, CanadadKiiko Matsumoto Acupuncture Clinic, 1223 Walnut Street, Newton Highlands, MA, 02461, USAbca r t i c l e i n f o

a b s t r a c t

Article history:
Received 21 May 2015
Accepted 3 July 2015

To study the biological effects of acupuncture on depression, we hypothesized that acupuncture will
exert its antidepressant effect through a bottom-up neuromodulation of the autonomic dysfunction in
depression. The participants received press needle (PN) acupuncture for 72 h continuously in a shamcontrolled design. Psychological assessments and Holter electrocardiography were performed before
and after PN acupuncture. We evaluated their autonomic functions through the heart rate variability(HRV). As a result, following PN acupuncture participants showed signiﬁcant improvement in the Beck's
Depression Inventory scores (P ¼ 0.031), systolic/diastolic blood pressures (P ¼ 0.002/P ¼ 0.011), andcoefﬁcient of variation of the ReR interval (P < 0.0001), compared to sham PN. The present ﬁndings
showed PN acupuncture induced alterations in vagal function, blood pressure, and Beck's Depression
Inventory scores. It was suggested that vagal stabilization effect by acupuncture may be associated withthe therapeutic mechanism in depression.
© 2015 Elsevier Ltd. All rights reserved.

Keywords:
Autonomic function
Blood pressure
Medication-resistant depression
Holter electrocardiogram
Press needle acupuncture
Vagal function

1. Introduction
Affective disorder is a highly prevalent condition associatedwith large socioeconomic loss [1]. In October 2012, the World
Health Organization (WHO) estimated that more than 350 million
patients are suffering from depression worldwide. Antidepressantsand psychotherapy are typically administered for depression andare effective in many patients. However, approximately 10e40% of
patients remain signiﬁcantly treatment-resistant [2].
1.1. Acupuncture and depression
The therapeutic effect of acupuncture on depression is wellknown empirically, however, evidence from randomized controlled
trials (RCTs) is relatively limited [3e7]. Further, acupuncturereportedly affects the autonomic nervous system, but the* Corresponding author. Laboratory of Neuromodulation, Kanagawa PsychiatricCenter, 2-5-1 Serigaya, Kohnan-ku, Yokohama, 233-0006, Japan.
E-mail address: motoaki@motoaki.com (M. Nakamura).
http://dx.doi.org/10.1016/j.ctcp.2015.07.002
1744-3881/© 2015 Elsevier Ltd. All rights reserved.

therapeutic mechanism underlying this effect remains unknown[8] because of the variable results such as the effects on heatrate variability (HRV) from several sham-controlled RCTs [9].
Nevertheless, there are convincing prior studies demonstratingthat patients with major depression exhibited diminished parasympathetic reactivity and, presumably, increased sympathetic
reactivity [10,11]. Moreover, Wang et al. has reported that theseverity of depression was associated with the severity of autonomic dysfunction [11].
1.2. Press needle acupuncture
Press needle (PN) is a special acupuncture needle, which has
been developed in Japan by improving the conventional intradermal needles (see Fig. 1). PN can stimulate the targeted acupoints
continuously for a few days in a non-invasive and safe way [12], andfurther it enable us to apply acupuncture in a double-blind, placebo-controlled design by using sham PN. Indeed, there are several
clinical studies using PN for various diseases. For example, Anders
n) to alleviate the symptom of
et al. applied active PN to PC6 (neigua
acute vomiting in children with gastroenteritis and pneumonia,

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Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200

Abbreviations
ANOVA
BDI-II
BP
CSI
CVI
CVRR
DBP
ECG
ECT
HC
HF
HR

Analysis of variance
Beck's depression inventory, 2nd edition
Blood pressure
Cardiac sympathetic index
Cardiac vagal index
Coefﬁcient of variation of the ReR interval
Diastolic blood pressure
Electrocardiogram
Electroconvulsive therapy
Healthy control
High frequencies
Heart rate

HRV
ICD-10
JIS
LF
LF/HF
PN
RCT
SBP
STAI
TMI
VLF
VNS
WHO

Heart rate variability
International Classiﬁcation of Disease, 10th edition
Japanese Industrial Standard
Low frequencies
Ratio of low- to high-frequency powerPress needle
Randomized controlled trial
Systolic blood pressureState-Trait Anxiety Inventory
Toho Medical Index
Very low frequency
Vagal nerve stimulation
World Health Organization

Fig. 1. The left ﬁgure shows the appearance of the PN (Pyonex; Seirin Co., Ltd.). The middle ﬁgure shows the appearance of an active PN with an acupuncture needle while the rightﬁgure shows a sham PN without an acupuncture needle.

which resulted in clinical improvement with feasibility and highacceptance for these children [13]. In other case series study, they chí) with active PN for treatment of hospitalstimulated at LI11 (Quinduced constipation in children and observed a remarkable effectin all children within 2 h after active PN intervention [14]. Further, arandomized, double-blind, placebo-controlled trial using active or ) for patients with lower
sham (i.e., placebo) PN to BL23 (shenshuback pain has shown a signiﬁcant effect for pain relief and also
active and sham PNs were indistinguishable for the subjects [15].
1.3. Objectives of the present study
With this background, we intended to verify the therapeutic
effects of acupuncture on depression and investigate its therapeuticmechanism for depression by employing PN approach in the shamcontrolled design described below. In this study, we hypothesized
the following therapeutic mechanism of PN acupuncture fordepression: PN acupuncture stimulates the somatosensory nerves
through multimodal receptors in the skin; thereby this somatosensory afferent input indirectly neuromodulates the autonomic
nervous system [16e18]; thus the neuromodulated autonomic
function (primarily through a vagal nervous function) indirectly
provides an antidepressant effect [19,20].
2. Material and methods
2.1. Study participants
Twelve healthy participants and 30 inpatients withmedication-resistant depression, who were recruited from

Kanagawa Psychiatric Center (Yokohama, Japan), have participated in this sham-controlled study. Diagnosis was determined bycertiﬁed psychiatrists based on the International Classiﬁcation of
Disease, 10th edition (ICD-10). In this study, we deﬁned
medication-resistant depression as the lack of response to morethan 2 antidepressants over 3 months and a persistent depressive
state. Of the 30 patients (16 men and 14 women; mean ± standard
deviation, 50 ± 11 years old), 20 had monopolar depression, 2 hadbipolar I depression, 4 had bipolar II depression, and 4 had dysthymia in the diagnosis. For patients group, the inclusion criteria
were i) patients who have diagnosis of depression, ii) score over 11(this is a cutoff value for autonomic dysfunction) in the Toho
Medical Index (TMI) [21] for either autonomic nerve symptoms(factor A) or psychiatric symptoms (factor P), and iii) enoughconsent capacity for this study. The exclusion criteria were otherpsychiatric comorbidities; a history of seizure, epilepsy, severe or
acute medical illnesses, neurological disorders, alcohol or otherdrug dependence; or electroconvulsive therapy (ECT) within 6months of the study. All patients received antidepressantsthroughout the study period but the type and dose of medication
remained constant. The mean imipramine equivalent dose of theantidepressant [22] in the patients group was 96.1 ± 25.8 mg. The
healthy control (HC) group comprised 12 healthy participants (5men and 7 women; 36 ± 8 years) with no history of depression or
any of the exclusion criteria. There were no dropouts in this study.
The study design was reviewed by the local ethics committee of
Kanagawa Psychiatric Center and the committee approved thisstudy. The study was carried out in accordance with the latest
version of the Declaration of Helsinki, and informed consent of theparticipants was obtained after the nature of the procedures had

Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200

been fully explained.
2.2. Psychological assessments
Before the entry of the study, all participants underwent the TMI
questionnaire. The TMI is a self-report medical inventory focusedon autonomic symptoms [21]. The TMI measures two types ofautonomic symptoms: 1) factor A (i.e., autonomic physical symptoms), and 2) factor P (i.e., autonomic psychiatric symptoms).
Higher scores indicate higher levels of autonomic dysfunction, andthe cutoff score is 11 for each factor (A and P). Before and after PN
acupuncture, all participants answered the Beck's Depression Inventory II (BDI-II) and the State-Trait Anxiety Inventory (STAI).
Here, the Beck Depression Inventory is a 21-question multiplechoice self-report inventory [23] that is one of the most widelyused measures for the severity of depression, and the STAI is a selfreport psychological inventory focused on anxiety symptoms [24].
The STAI measures two types of anxiety: 1) state anxiety (i.e.,anxiety about an event), and 2) trait anxiety (i.e., anxiety level as apersonal characteristic). Higher scores are positively correlatedwith higher levels of anxiety. State anxiety can be deﬁned as fear,
nervousness, discomfort, and autonomic nervous system arousal
induced by different situations. Trait anxiety can be deﬁned as
feelings of stress, worry, and discomfort experienced on a day-today basis.
2.3. Biological measures
Blood pressure (BP) and heart rate (HR) were measured before
and after PN acupuncture by blood pressure monitors (Omron
Healthcare Co., Ltd., Kyoto, Japan), and Holter electrocardiogram(ECG) (CarPod; Medilink Co., Ltd., Toyota, Japan) was recorded with
2 surface electrode channels to evaluate autonomic nervous system
function. From the ECG data, we analyzed the coefﬁcient of variation of the ReR interval (CVRR), cardiac vagal index (CVI), cardiac
sympathetic index (CSI), very low frequency (VLF), and the ratio of
powers of low-frequency to high-frequency band (LF/HF) [25,26].
These HRV indices provide physiological information on the autonomic functions of the heart, which reﬂect sympathetic and parasympathetic functions as well as their interaction [27,28]. Fig. 2
shows a schematic of the study design.
2.4. PN acupuncture procedure
PN acupuncture has been developed in Japan by improving theintradermal indwelling needle as a non-invasive method to stimulate acupoints for a long-term (typically a few days). Recently it
has been widely used for various diseases, especially as auricularacupuncture, throughout the world due to its feasibility and highacceptance of the patients [12e15]. Further, the PN has an advantage of extremely low risk for peripheral nerve injury due to theneedle insertion. Further, there is another advantage in PN of being

195

able to perform a sham-controlled acupuncture study by using
elaborated sham PN. Taking advantage of such features of PN, weapplied disposable seal-type PNs (Pyonex; Seirin Co., Ltd., Shizuoka
City, Japan), which are in accordance with the Japanese Industrial
Standard. The active PN has a length of 0.6 mm and a diameter of
0.2 mm needle, whereas the sham PN has no needle to stimulate.
Fig. 1 shows the appearance of the PN. We performed theacupuncture treatment for “head blood stagnation” (“Tobu-Oketsu”
in Japanese) in the Kiiko-style, Japanese acupuncture, which was
proposed by Matsumoto and Nagano, to the participants, because
the pathological manifestation of “head blood stagnation” isthought to be associated with the symptoms of depression in thatJapanese acupuncture medicine [29]. Here, the condition of “headblood stagnation” in Eastern Medicine is the very similar concept toedema, congestion, and circulatory disturbance of the head inWestern Medicine [29]. Thus, we applied the PNs to the followingnlǐ) in both arms and SP9
acupoints; PC4 (xìmen) and LI10 (shǒusa
n) and SP6 (sanyınjia
o) in both legs [30e32]. More(yınlíngqua
speciﬁcally, PC4 (xìmen) is thought to be related to general cardiacnlǐ) is assumed to be strongly associatedfunction [33]; LI10 (shǒusa
with sympathoexcitatory pressor responses mediated through then) is thought
rostral ventral lateral medulla [34,35]; SP9 (yınlíngqua
to be strongly associated with heart rate deceleration and phasic
sympathetic activation represented by skin conductance responsenyınjia
o) is thought to be related to the modulation of[36]; SP6 (saautonomic nervous system function, especially in women withprimary dysmenorrhea [37]. All participants received PN
acupuncture for the 8 acupoints described above for 3 days
continuously. Patients with depression and healthy controls (HC)were assigned almost equally to the active PN stimulation group or
sham PN stimulation group with age and sex matched (age:t40 ¼ 1.548, P ¼ 0.130; sex: c2 ¼ 2.381, P ¼ 0.123).
2.5. Holter ECG signal processing and data analysis
All participants underwent Holter ECG recording (acquisition
sampling rate; 512 Hz) for 1 h before and after the PN acupuncture.
Holter ECG recordings were performed in the morning after
breakfast in the bed rest with awake state at mild room temperature. Holter ECG data were analyzed at Medilink Co., Ltd. and theanalysts were completely blinded to the participants' group as wellas their PN acupuncture intervention. Data were manually preprocessed before ECG analysis as follows; the analysis only included
the part of recordings of sufﬁcient data quality for evaluation. The
RR intervals were manually conﬁrmed after classifying the QRSmorphology. Only sequences with normal QRS characteristics wereanalyzed for the HRV study. The CVRR was obtained from theanalysis of the time domain and calculated as the standard deviation of all RR intervals between the two normal QRS complexes. The
CVI and CSI were calculated according to prior studies [38,39]. The
fast Fourier transform was applied in power spectrum analysis toconvert the different successive RR intervals in the frequency

Fig. 2. This schematic shows the experimental design of the PN study.

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Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200

domain. It is known that vagal and sympathetic activities affect low
frequencies (LF: 0.04e0.15 Hz), whereas vagal tone only affects highfrequencies (HF: 0.15e0.4 Hz). The LF/HF ratio is an indicator of
sympathovagal balance, and oscillations in very low frequencies(VLF; 0.003e0.04 Hz) reﬂect the ﬂuctuation of the vagal basoreﬂex
sensitivity in a steady state [40].
2.6. Statistical analysis
Each biological and psychological measure was comparedlongitudinally (i.e., before and after the PN intervention) and crosssectionally (i.e., between HCs and patients with depression) using
3-way repeated measure analysis of variance (ANOVA) with “time”
as a within-subject factor, and “intervention” (active vs. sham PN)
and “group” (HCs vs. depression) as the between-subject factors.
Post-hoc independent t-tests were performed for signiﬁcant
ANOVA results. Next, we also performed analysis of covariance(ANCOVA) model that incorporated age factor as covariate into thesame three-way ANOVA model for the analysis of cross-sectional
comparison between HC and depression groups (i.e., main effectof group), since we did not match age between both groups (group:t40 ¼ 3.901, P < 0.0001). Further, Pearson's correlation analysis
was performed between the percent changes of each value for eachgroup (HC and depression) as well as subgroup (active and sham PN
acupuncture). A conservative p-value (0.01) was used as a signiﬁcance level in this analysis. Statistical procedures were performed
using the SPSS software (SPSS Japan Inc., Tokyo, Japan).
3. Results
3.1. Psychological outcomes
Table 1 contains descriptive data of the psychological tests.
Table 2 shows the results of 3-way ANOVA for the psychologicaltests. The 3-way ANOVA indicated a signiﬁcant time-byintervention interaction in the BDI-II and a main effect of groupwith no main effect of time. Further, signiﬁcant main effects ofgroup in the state and trait of the STAI assessments were observed,
whereas no signiﬁcant time-by-intervention interactions wereshown in the state and trait in the STAI assessments. Post-hoc independent t-tests for the percent changes in the score of the BDI-II
by the PN intervention showed a following signiﬁcant result. In thesubgroup of active PN acupuncture, the percent improvement of
the score in the BDI-II (34.3% ± 36.8%) was signiﬁcantly better(t40 ¼ 3.524, P ¼ 0.001) than those of the subgroup of sham PN
acupuncture (5.7% ± 36.8%).

3.2. Blood pressure and heart rate
Table 1 shows the descriptive data of blood pressure and heartrate. Table 2 shows the results of 3-way ANOVA for blood pressureand heart rate. The ANOVA indicated signiﬁcant time-byintervention interactions in systolic blood pressure (SBP) and diastolic blood pressure (DBP), but not in HR. There was no signiﬁcant
ﬁnding in the main effects of time, group, and intervention. Posthoc independent t-tests for the percent changes in the SBP and
DBP following the 3-days PN intervention showed signiﬁcant hypotensive effects for both SBP and DBP in the subgroup of active PN
acupuncture (SBP: t40 ¼ 3.307, P ¼ 0.002; DBP: t40 ¼ 3.053,
P ¼ 0.004). Also, the percent changes in SBP and DBP in the subgroup of active PN acupuncture (SBP, 4.1% ± 4.0%;
DBP, 6.3% ± 6.8%) were signiﬁcantly lower than those in thesubgroup of sham PN (SBP, 0.9% ± 5.5%; DBP, 1.6% ± 9.5%). Of note,the active PN acupuncture induced hypotensive effects for both SBP
and DBP, however, these BP maintained the normal ranges in allparticipants during and after the active PN intervention. On theother hand, no signiﬁcant effect was observed in HR with active PN.
Moreover, there were no signiﬁcant correlations between age andthe value of BP, HR, and these change by PN.
3.3. Autonomic function outcomes
Table 1 shows the descriptive data of autonomic functions.
Table 2 shows the results of 3-way ANOVA for each index of autonomic functions. The ANOVA for CVRR and CVI indicated a significant time-by-intervention interaction and main effects of groupwith no signiﬁcant main effects of time and intervention. However,the ANOVA for VLF showed a signiﬁcant main effect of group withno signiﬁcant time-by-intervention interaction or main effect oftime. The ANOVA for CSI and LF/HF showed no signiﬁcant time-byintervention interactions or main effects of time, group, andintervention. The ANCOVA that incorporated age factor as covariate
between the group of HCs and patients with depression indicatedsigniﬁcant main effects of group in CVRR (F1, 37 ¼ 11.318, P ¼ 0.002),
CVI (F1, 37 ¼ 4.218, P ¼ 0.047), and VLF (F1, 37 ¼ 5.314, P ¼ 0.027)
whereas no signiﬁcant main effects of group in CSI and LF/HF. The
independent t-tests for the percent changes in CVRR and CVI
following the 3-days PN intervention revealed that the percent
changes in CVRR and CVI in the subgroup of active PN acupuncture(CVRR: 24.3% ± 26.6%, t40 ¼ 5.194, P < 0.0001; CVI: 6.2% ± 8.1%,
t40 ¼ 3.014, P ¼ 0.004) were signiﬁcantly better than those in thesubgroup of sham PN intervention (CVRR: 10.7% ± 15.8%;
CVI: 2.8% ± 11.0%). These results indicate that active PN
acupuncture can signiﬁcantly improve the vagal function indexed

Table 1
Demographic results of psychological tests, hemodynamics, and autonomic function between healthy controls (active vs. sham PTN) and patients with depression (active vs.
sham PTN) before and after PTN intervention.
Indices

Healthy controls

Patients with depression

Active PTN (N ¼ 6)

BDI-IIState of STAI
Trait of STAI
SBP [mmHg]
DBP [mmHg]
HR [bpm]
CVRR [%]CVI
VLF

Sham PTN (N ¼ 6)

Active PTN (N ¼ 15)

Sham PTN (N ¼ 15)

Pre

Post

Pre

Post

Pre

Post

Pre

Post

4.3 ± 4.2
39.2 ± 5.5
39.2 ± 5.2
116 ± 874 ± 668 ± 78.9 ± 2.8
3.8 ± 0.41416 ± 1008

1.0 ± 2.0
40.5 ± 3.8
39.7 ± 5.0
111 ± 1070 ± 7*68 ± 810.0 ± 2.6
3.8 ± 0.4
1718 ± 1300

3.2 ± 2.9
38.5 ± 9.1
37.5 ± 7.7
118 ± 1076 ± 967 ± 98.7 ± 2.8
3.6 ± 0.4829 ± 474

4.0 ± 4.4
37.5 ± 8.4
37.2 ± 7.5
121 ± 878 ± 569 ± 78.4 ± 2.7
3.7 ± 0.31021 ± 530

32.1 ± 11.9
54.9 ± 12.3
60.1 ± 12.9
124 ± 1880 ± 1671 ± 65.0 ± 1.4
3.2 ± 0.3435 ± 177

22.5 ± 11.4*
51.6 ± 14.0
56.7 ± 11.6
119 ± 16*74 ± 14*71 ± 56.4 ± 2.8*
3.5 ± 0.3*594 ± 265*25.5 ± 14.8
51.3 ± 16.2
56.1 ± 15.0
128 ± 1382 ± 1069 ± 105.2 ± 1.7
3.4 ± 0.4582 ± 480

25.5 ± 15.9
51.5 ± 14.3
56.3 ± 13.8
128 ± 1382 ± 1070 ± 104.4 ± 1.6*
3.2 ± 0.6469 ± 436*

*Signiﬁcant ﬁndings in paired t-test between pre and post PTN acupuncture. (P < 0.05).

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197

Table 2
Results of the 3-way ANOVA for the results of psychological tests, blood pressure and heart rate, autonomic functions with time as a within-subject factor and intervention(active vs. sham PTN acupuncture) and group (healthy controls vs. patients with depression) as between-subjects factors.
Outcome of indices

Main effect of time

Main effect of group

Main effect of intervention

Time  intervention

Time  group

Time  intervention  group

BDI-IIF1, 38 ¼ 3.780
P ¼ 0.059
F1, 38 ¼ 0.164
P ¼ 0.687
F1, 38 ¼ 0.214
P ¼ 0.646
F1, 38 ¼ 3.343
P ¼ 0.075
F1, 38 ¼ 2.750
P ¼ 0.106
F1, 38 ¼ 1.166
P ¼ 0.287
F1, 38 ¼ 3.054
P ¼ 0.089
F1, 38 ¼ 1.152
P ¼ 0.290
F1, 38 ¼ 0.002
P ¼ 0.969
F1, 38 ¼ 0.350
P ¼ 0.558
F1, 38 ¼ 0.386
P ¼ 0.538

F1, 38 ¼ 38.636
P < 0.002*
F1, 38 ¼ 11.295
P ¼ 0.002*
F1, 38 ¼ 25.563
P < 0.0001*
F1, 38 ¼ 3.011
P ¼ 0.091
F1, 38 ¼ 1.435
P ¼ 0.238
F1, 38 ¼ 0.856
P ¼ 0.361
F1, 38 ¼ 28.282
P < 0.0001*
F1, 38 ¼ 10.986
P ¼ 0.002*
F1, 38 ¼ 0.238
P ¼ 0.628
F1, 38 ¼ 16.025
P ¼ 0.00028*
F1, 38 ¼ 1.621
P ¼ 0.211

F1, 38 ¼ 0.014
P ¼ 0.907
F1, 38 ¼ 0.215
P ¼ 0.646
F1, 38 ¼ 0.327
P ¼ 0.571
F1, 38 ¼ 3.450
P ¼ 0.071
F1, 38 ¼ 1.701
P ¼ 0.200
F1, 38 ¼ 0.090
P ¼ 0.766
F1, 38 ¼ 1.597
P ¼ 0.214
F1, 38 ¼ 0.687
P ¼ 0.412
F1, 38 ¼ 0.018
P ¼ 0.893
F1, 38 ¼ 3.034
P ¼ 0.090
F1, 38 ¼ 0.182
P ¼ 0.672

F1, 38 ¼ 5.003
P ¼ 0.031*
F1, 38 ¼ 0.026
P ¼ 0.873
F1, 38 ¼ 0.196
P ¼ 0.660
F1, 38 ¼ 11.564
P ¼ 0.002*
F1, 38 ¼ 7.200
P ¼ 0.011*
F1, 38 ¼ 2.343
P ¼ 0.134
F1, 38 ¼ 16.383
P ¼ 0.00025*
F1, 38 ¼ 4.846
P ¼ 0.034*
F1, 38 ¼ 1.088
P ¼ 0.304
F1, 38 ¼ 3.033,
P ¼ 0.090
F1, 38 ¼ 0.324
P ¼ 0.573

F1, 38 ¼ 1.281
P ¼ 0.265
F1, 38 ¼ 0.25
P ¼ 0.620
F1, 38 ¼ 0.264
P ¼ 0.610
F1, 38 ¼ 0.645
P ¼ 0.427
F1, 38 ¼ 0.568
P ¼ 0.456
F1, 38 ¼ 0.0001
P ¼ 0.991
F1, 38 ¼ 0.060
P ¼ 0.808
F1, 38 ¼ 0.052
P ¼ 0.821
F1, 38 ¼ 0.186
P ¼ 0.669
F1, 38 ¼ 0.002
P ¼ 0.964
F1, 38 ¼ 0.512
P ¼ 0.479

F1, 38 ¼ 0.779
P ¼ 0.383
F1, 38 ¼ 0.673
P ¼ 0.417
F1, 38 ¼ 0.486,
P ¼ 0.490
F1, 38 ¼ 1.087
P ¼ 0.304
F1, 38 ¼ 0.0009
P ¼ 0.976
F1, 38 ¼ 0.062
P ¼ 0.805
F1, 38 ¼ 1.007
P ¼ 0.322
F1, 38 ¼ 3.938
P ¼ 0.054
F1, 38 ¼ 3.247
P ¼ 0.079
F1, 38 ¼ 0.545
P ¼ 0.465
F1, 38 ¼ 0.031
P ¼ 0.862

State of STAI
Trait of STAI
SBP [mmHg]
DBP [mmHg]
HR [bpm]
CVRR
CVI
CSI
VLF
LF/HF

*Signiﬁcant ﬁndings in the ANOVA (P < 0.05); bmp: beat per minute.

by CVRR and CVI. Fig. 3 shows the scatter plots that demonstrate
the PN-induced changes in BDI-II, SBP/DBP, and CVRR/CVI between
the subgroup of active and sham PN acupuncture. Further, post-hoc
independent t-tests for CVRR, CVI, and VLF before and after the PN
acupuncture demonstrated that the group of depression had
signiﬁcantly worse values of CVRR (pretreatment: t40 ¼ 5.641,
P < 0.0001; posttreatment: t40 ¼ 4.488, P < 0.0001), CVI (pretreatment: t40 ¼ 3.318, P ¼ 0.002; posttreatment: t40 ¼ 2.877,
P ¼ 0.006), and VLF (pretreatment: t40 ¼ 3.416, P ¼ 0.001; posttreatment: t40 ¼ 3.994, P < 0.0001), compared to the group of HC.
That is, patients with depression had signiﬁcantly lower vagal
functions indexed by CVRR, CVI, and VLF, compared to HC.

3.4. Clinical correlations
The correlation analysis was conducted between percent
changes in the BDI-II, SBP, DBP, CVRR, and CVI, because these
indices showed signiﬁcant changes following active PN acupuncture. There were signiﬁcant correlations between the percent
changes in SBP and DBP (r ¼ 0.588, P ¼ 0.005, N ¼ 21) and thepercent changes in CVRR and CVI (r ¼ 0.678, P ¼ 0.001, N ¼ 21).
However, signiﬁcant correlations were not observed among thepercent changes in BDI-II scores, blood pressure (SBP and DBP), andvagal nerve function (CVRR and CVI). In addition, subanalysis
showed a signiﬁcant correlation between percent improvements in

Fig. 3. (A) Scatter plots of the PN-induced changes in the BDI-II score between the subgroup of active and sham PN. (B and C) The scatter plots indicate the PN-induced changes in
SBP and DBP, respectively, and (D and E) in CVRR and CVI, respectively. BDI-II ¼ Beck's Depression Inventory II; CVI ¼ cardiac vagal index; CVRR ¼ coefﬁcient of variation of the ReR
interval; DBP ¼ diastolic blood pressure; PN ¼ Press Needle; SBP ¼ systolic blood pressure.

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the traits of STAI and VLF (r ¼ 0.615, P ¼ 0.003, N ¼ 21) in thesubgroup of active PN acupuncture [Fig. 4(A)]. However, no signiﬁcant correlation was observed in the subgroup of sham PN.
Further, following the active PN acupuncture, there was a signiﬁcant correlation between percent improvements in the state of the
STAI assessment and CSI (r ¼ 0.646, P ¼ 0.009, N ¼ 15) in the groupof depression [Fig. 4(B)]. However, no signiﬁcant correlation wasobserved between the two in the subgroup of sham PN.
3.5. Adverse effects
Adverse effects such as autonomic dysfunction, abnormal hypotension, and skin disorder were not observed with the intervention of PN acupuncture in the study.
4. Discussion
4.1. Study ﬁndings
The present study generated several signiﬁcant ﬁndings. First,
active PN acupuncture demonstrated a signiﬁcant improvement on
the BDI-II scores, a signiﬁcant reduction on the SBP/DBP which
remained within the normal range, and a signiﬁcant improvementof vagal nervous function on the CVRR and CVI, compared to sham
PN acupuncture. Second, we conﬁrmed that patients with depression exhibited signiﬁcantly worse scores of the BDI-II, state andtrait of the STAI assessments, as well as signiﬁcantly lower values in
the CVRR, CVI, and VLF. These latter results of autonomic functions
suggest vagal nervous dysfunction in patients with depression, as
reported in previous studies [40,41]. Further, we did not observe asigniﬁcant sympathetic inhibition measured with CSI following
active PN acupuncture intervention, however, there was a clinicalcorrelation between improvement of anxiety symptoms in thescore of state in the STAI and sympathetic inhibition (i.e., decreasein value of CSI) in patients with depression. Therefore, it was
speculated that sympathetic inhibition may also play a role in thetherapeutic mechanism of acupuncture in depression. Moreover,signiﬁcantly lower value of VLF in patients with depression may berelated to dysfunctional homeostatic regulation of blood pressure,since the VLF is considered to reﬂect the capacity of vagal basoreﬂex sensitivity [42].
It is well known that there is an aging effect on autonomic
function in a direction of worsening. In the cross-sectional analysis
between HCs and patients with depression, since age was notmatched between both groups, we tried to reconcile thisconfounding effect by applying the ANCOVA model that included
age as covariate. As a result, we still observed signiﬁcant main effects of CVRR, CVI, and VLF in this comparison analysis between thetwo groups. It means that patients with depression had worse vagal
functions compared to HCs, even considering the confounding
factors by age in this study.
Furthermore, as an important aspect in depression associatedwith vagal nerve function, consideration should be given to the side
effects of antidepressants, because most antidepressants canadversely affect the autonomic function [43], especially on vagal
nerve function [44] (i.e., values of CVRR and CVI decreased).
However, practically it is very difﬁcult to discontinue or taper theantidepressants in those inpatients with depression for the study to
exclude the inﬂuence of antidepressants on autonomic functions.
Therefore, in this study we applied a sham-controlled design toevaluate effects of active PN acupuncture on autonomic functions.
As a result, compared to sham PN, active PN acupuncture demonstrated a signiﬁcant improvement effect on vagal nerve function,
which also partially correlated with the improvement of SAI score[Fig. 4(A)]. That is, our ﬁnding suggests that active PN acupuncture
has a potential effect to improve vagal function surpassing theabove mentioned adverse effect on vagal function ofantidepressants.
In this study, there was no signiﬁcant correlation between the
improvement of BDI-II score and vagal nerve function measured
with ECG. Thus, we need to interpret the relationship between theantidepressant effect and improvement of vagal function byacupuncture carefully. Although there is a limit in our ﬁndings,
given the evidence of previous studies that suggesting the relationship among acupuncture, depression, and autonomic functions[10,11,16e20], the biological rationale for the therapeutic effect of
PN acupuncture, which may be associated with the improvement ofvagal nerve function, could be explained from the following
promising evidence (e.g., da Silva and Dorsher, 2014). To be speciﬁc,for example, it is known that vagal nerve stimulation (VNS) therapy
can cause an antidepressant effect in patients with treatmentresistant depression [45,46] and induce a signiﬁcant increase in
CVRR by modulating the sympathovagal balance in the central
nervous system [47]. Apparently, there is a large methodologicaldifference in their intervention between the acupuncture and VNS,
however, it is presumed that both treatments share a common
therapeutic mechanism for depression in terms of the neuromodulating effect on vagal nerve function [18,19,48]. Thus, theimprovement of vagal nerve function may be associated with theunderlying therapeutic mechanism of acupuncture for depression

Fig. 4. (A) Pearson's correlation analysis indicates a signiﬁcant inverse correlation between percent changes in the STAI trait and VLF (r ¼ 0.615, P ¼ 0.003, N ¼ 21) in the subgroupof active PN acupuncture. (B) The analysis indicates a signiﬁcant positive correlation between percent change in the STAI state and CSI (r ¼ 0.646, P ¼ 0.009, N ¼ 15) in patients withdepression in the subgroup of active PN acupuncture. CSI ¼ cardiac sympathetic index; PN ¼ Press Needle; STAI ¼ State-Trait Anxiety Inventory; VLF ¼ very low frequency.

Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200

as well [19,20]. Further, the hypotensive effect of the PN acupuncture within normal range may be induced by improving theimbalance of autonomic function primarily through the vagal stabilization modulated by active PN acupuncture [17e19].
Although the 0.6 mm length of PN seems subtle acupuncture
stimulation toward acupoints, the observed clear difference in HRVchanges between active and sham PN suggests the validity of thisnon-invasive style of acupuncture. The most distinguished utility of
the PN is that it enables an ideal sham condition in acupuncture
study. Such a double-blind sham-controlled design using the PN
should be applied to future acupuncture studies to investigate
biological mechanisms of speciﬁc acupoints of interest.
4.2. Study limitations
There are several limitations in this study. First, the sample size
was relatively small. Second, the patients with depression received
medication. The confounding effect of medication was not
excluded. Third, we could not demonstrate the long-term effects ofactive PN acupuncture because we only performed biological andpsychological assessments before and 3 days after the PN
intervention.
5. Conclusions
Collectively, despite the above limitations, it is suggested that
active PN acupuncture may exert its therapeutic effects on
depression by improving the vagal nerve function through abottom-up neuromodulation. RCTs with large sample sizes areneeded to establish the beneﬁts of acupuncture as a more reliable
complementary treatment for depression.
Funding statement
This research was supported in part by a grant from the Pﬁzer
Health Research Foundation.
Contributors
Y.N. and M.N. were involved in conception and design of thestudy. Y.N., T.I., Y.T., and M.N. recruited the participants and performed clinical assessments. H.M., A.I., Y.S., and A.S. performed PN
acupuncture. Y.N., T.I., Y.T., and S.H. measured Holter ECG, BP, and
HR. Y.N. performed statistical analysis. Y.N., K.M., and M.N. interpreted the results of study. Y.N. prepared ﬁgures and drafted themanuscript. Y.N. and M.N. edited and revised manuscript. All authors have approved ﬁnal version of manuscript.
Conﬂict of interest statement
All authors have no conﬂicts of interest to declare in this study.
Acknowledgments
We would like to thank Ms. Misa Inoue, Ms. Chiaki Osawa, Ms.
Yukari Sawada, Mr. Gen Ishii for their clinical support, and SeirinCo., Ltd for their technical advice. We also would like to appreciate
Mr. Shirou Obata and Mr. Yasuhiro Ochi of MEDILINK Co., Ltd fortheir technical support.
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