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Acupuncture-induced changes of vagal function in patients with depression: a preliminary sham-controlled study with press needles

Contents lists available at Complementary Therapies in Clinical Practice Acupuncture-induced changes of vagal function in patients withdepression: A preliminary sham-controlled study with press needles Yoshihiro Noda , Takuji Izuno Yoshie Tsuchiya , Shunsuke Hayasaka ,Kiiko Matsumoto Hirohiko Murakami , Arata Ito , Yukari Shinse , Aya Suzuki ,Motoaki Nakamura , * a Kanagawa Psychiatric Center, 2-5-1 Serigaya, Kohnan-ku, Yokohama, Kanagawa, 233-0006, Japanb Department of Neuropsychiatry, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japanc Centre for Addiction and Mental Health, Department of Psychiatry, University of Toronto, 1001 Queen Street West, Toronto, ON, M6J 1H4, Canadad Kiiko Matsumoto Acupuncture Clinic, 1223 Walnut Street, Newton Highlands, MA, 02461, USA To study the biological effects of acupuncture on depression, we hypothesized that acupuncture will Received 21 May 2015 exert its antidepressant effect through a bottom-up neuromodulation of the autonomic dysfunction in Accepted 3 July 2015 depression. The participants received press needle (PN) acupuncture for 72 h continuously in a sham-controlled design. Psychological assessments and Holter electrocardiography were performed before and after PN acupuncture. We evaluated their autonomic functions through the heart rate variability Autonomic function (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), and coefficient of variation of the R Holter electrocardiogram eR interval (P < 0.0001), compared to sham PN. The present findings Press needle acupuncture 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.
therapeutic mechanism underlying this effect remains unknownbecause of the variable results such as the effects on heat Affective disorder is a highly prevalent condition associated rate variability (HRV) from several sham-controlled RCTs .
with large socioeconomic loss In October 2012, the World Nevertheless, there are convincing prior studies demonstrating Health Organization (WHO) estimated that more than 350 million that patients with major depression exhibited diminished para- patients are suffering from depression worldwide. Antidepressants sympathetic reactivity and, presumably, increased sympathetic and psychotherapy are typically administered for depression and reactivity . Moreover, Wang et al. has reported that the are effective in many patients. However, approximately 10e40% of severity of depression was associated with the severity of auto- patients remain significantly treatment-resistant nomic dysfunction 1.2. Press needle acupuncture 1.1. Acupuncture and depression Press needle (PN) is a special acupuncture needle, which has The therapeutic effect of acupuncture on depression is well been developed in Japan by improving the conventional intrader- known empirically, however, evidence from randomized controlled mal needles (see ). PN can stimulate the targeted acupoints trials (RCTs) is relatively limited . Further, acupuncture continuously for a few days in a non-invasive and safe way , and reportedly affects the autonomic nervous system, but the further it enable us to apply acupuncture in a double-blind, pla-cebo-controlled design by using sham PN. Indeed, there are severalclinical studies using PN for various diseases. For example, Anders * Corresponding author. Laboratory of Neuromodulation, Kanagawa Psychiatric et al. applied active PN to PC6 (n
an) to alleviate the symptom of Center, 2-5-1 Serigaya, Kohnan-ku, Yokohama, 233-0006, Japan.
E-mail address: (M. Nakamura).
acute vomiting in children with gastroenteritis and pneumonia, 1744-3881/ 2015 Elsevier Ltd. All rights reserved.

Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200 Heart rate variability International Classification of Disease, 10th edition ANOVA Analysis of variance Japanese Industrial Standard Beck's depression inventory, 2nd edition Ratio of low- to high-frequency power Cardiac sympathetic index Cardiac vagal index Randomized controlled trial Coefficient of variation of the ReR interval Systolic blood pressure Diastolic blood pressure State-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 high Kanagawa Psychiatric Center (Yokohama, Japan), have partici- acceptance for these children In other case series study, they pated in this sham-controlled study. Diagnosis was determined by stimulated at LI11 (Q uchí) with active PN for treatment of hospital- certified psychiatrists based on the International Classification of induced constipation in children and observed a remarkable effect Disease, 10th edition (ICD-10). In this study, we defined in all children within 2 h after active PN intervention . Further, a medication-resistant depression as the lack of response to more randomized, double-blind, placebo-controlled trial using active or than 2 antidepressants over 3 months and a persistent depressive sham (i.e., placebo) PN to BL23 (sh
u) for patients with lower state. Of the 30 patients (16 men and 14 women; mean ± standard back pain has shown a significant effect for pain relief and also deviation, 50 ± 11 years old), 20 had monopolar depression, 2 had active and sham PNs were indistinguishable for the subjects bipolar I depression, 4 had bipolar II depression, and 4 had dys-thymia in the diagnosis. For patients group, the inclusion criteria 1.3. Objectives of the present study were i) patients who have diagnosis of depression, ii) score over 11(this is a cutoff value for autonomic dysfunction) in the Toho With this background, we intended to verify the therapeutic Medical Index (TMI) for either autonomic nerve symptoms effects of acupuncture on depression and investigate its therapeutic (factor A) or psychiatric symptoms (factor P), and iii) enough mechanism for depression by employing PN approach in the sham- consent capacity for this study. The exclusion criteria were other controlled design described below. In this study, we hypothesized psychiatric comorbidities; a history of seizure, epilepsy, severe or the following therapeutic mechanism of PN acupuncture for acute medical illnesses, neurological disorders, alcohol or other depression: PN acupuncture stimulates the somatosensory nerves drug dependence; or electroconvulsive therapy (ECT) within 6 through multimodal receptors in the skin; thereby this somato- months of the study. All patients received antidepressants sensory afferent input indirectly neuromodulates the autonomic throughout the study period but the type and dose of medication nervous system thus the neuromodulated autonomic remained constant. The mean imipramine equivalent dose of the function (primarily through a vagal nervous function) indirectly antidepressant in the patients group was 96.1 ± 25.8 mg. The provides an antidepressant effect .
healthy control (HC) group comprised 12 healthy participants (5men and 7 women; 36 ± 8 years) with no history of depression or 2. Material and methods any of the exclusion criteria. There were no dropouts in this study.
The study design was reviewed by the local ethics committee of 2.1. Study participants 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 the medication-resistant depression, who were recruited from participants was obtained after the nature of the procedures had

Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200 been fully explained.
able to perform a sham-controlled acupuncture study by usingelaborated sham PN. Taking advantage of such features of PN, we 2.2. Psychological assessments applied disposable seal-type PNs (Pyonex; Seirin Co., Ltd., ShizuokaCity, Japan), which are in accordance with the Japanese Industrial Before the entry of the study, all participants underwent the TMI Standard. The active PN has a length of 0.6 mm and a diameter of questionnaire. The TMI is a self-report medical inventory focused 0.2 mm needle, whereas the sham PN has no needle to stimulate.
on autonomic symptoms . The TMI measures two types of shows the appearance of the PN. We performed the autonomic symptoms: 1) factor A (i.e., autonomic physical symp- acupuncture treatment for "head blood stagnation" ("Tobu-Oketsu" toms), and 2) factor P (i.e., autonomic psychiatric symptoms).
in Japanese) in the Kiiko-style, Japanese acupuncture, which was Higher scores indicate higher levels of autonomic dysfunction, and proposed by Matsumoto and Nagano, to the participants, because the cutoff score is 11 for each factor (A and P). Before and after PN the pathological manifestation of "head blood stagnation" is acupuncture, all participants answered the Beck's Depression In- thought to be associated with the symptoms of depression in that ventory II (BDI-II) and the State-Trait Anxiety Inventory (STAI).
Japanese acupuncture medicine Here, the condition of "head Here, the Beck Depression Inventory is a 21-question multiple- blood stagnation" in Eastern Medicine is the very similar concept to choice self-report inventory that is one of the most widely edema, congestion, and circulatory disturbance of the head in used measures for the severity of depression, and the STAI is a self- Western Medicine Thus, we applied the PNs to the following report psychological inventory focused on anxiety symptoms acupoints; PC4 (xìmen) and LI10 (shǒusanlǐ) in both arms and SP9 The STAI measures two types of anxiety: 1) state anxiety (i.e., (yınlíngquan) and SP6 (sanyınjiao) in both legs More anxiety about an event), and 2) trait anxiety (i.e., anxiety level as a specifically, PC4 (xìmen) is thought to be related to general cardiac personal characteristic). Higher scores are positively correlated function LI10 (shǒusanlǐ) is assumed to be strongly associated with higher levels of anxiety. State anxiety can be defined as fear, with sympathoexcitatory pressor responses mediated through the nervousness, discomfort, and autonomic nervous system arousal rostral ventral lateral medulla ; SP9 (yınlíngquan) is thought induced by different situations. Trait anxiety can be defined as to be strongly associated with heart rate deceleration and phasic feelings of stress, worry, and discomfort experienced on a day-to- sympathetic activation represented by skin conductance response anyınjiao) is thought to be related to the modulation of autonomic nervous system function, especially in women with 2.3. Biological measures acupuncture for the 8 acupoints described above for 3 days Blood pressure (BP) and heart rate (HR) were measured before continuously. Patients with depression and healthy controls (HC) and after PN acupuncture by blood pressure monitors (Omron were assigned almost equally to the active PN stimulation group or Healthcare Co., Ltd., Kyoto, Japan), and Holter electrocardiogram sham PN stimulation group with age and sex matched (age: (ECG) (CarPod; Medilink Co., Ltd., Toyota, Japan) was recorded with t40 ¼ 1.548, P ¼ 0.130; sex: c2 ¼ 2.381, P ¼ 0.123).
2 surface electrode channels to evaluate autonomic nervous systemfunction. From the ECG data, we analyzed the coefficient of varia- 2.5. Holter ECG signal processing and data analysis tion of the ReR interval (CVRR), cardiac vagal index (CVI), cardiacsympathetic index (CSI), very low frequency (VLF), and the ratio of All participants underwent Holter ECG recording (acquisition powers of low-frequency to high-frequency band (LF/HF) sampling rate; 512 Hz) for 1 h before and after the PN acupuncture.
These HRV indices provide physiological information on the auto- Holter ECG recordings were performed in the morning after nomic functions of the heart, which reflect sympathetic and para- breakfast in the bed rest with awake state at mild room tempera- sympathetic functions as well as their interaction . ture. Holter ECG data were analyzed at Medilink Co., Ltd. and the shows a schematic of the study design.
analysts were completely blinded to the participants' group as wellas their PN acupuncture intervention. Data were manually pre- 2.4. PN acupuncture procedure processed before ECG analysis as follows; the analysis only includedthe part of recordings of sufficient data quality for evaluation. The PN acupuncture has been developed in Japan by improving the RR intervals were manually confirmed after classifying the QRS intradermal indwelling needle as a non-invasive method to stim- morphology. Only sequences with normal QRS characteristics were ulate acupoints for a long-term (typically a few days). Recently it analyzed for the HRV study. The CVRR was obtained from the has been widely used for various diseases, especially as auricular analysis of the time domain and calculated as the standard devia- acupuncture, throughout the world due to its feasibility and high tion of all RR intervals between the two normal QRS complexes. The acceptance of the patients . Further, the PN has an advan- CVI and CSI were calculated according to prior studies The tage of extremely low risk for peripheral nerve injury due to the fast Fourier transform was applied in power spectrum analysis to needle insertion. Further, there is another advantage in PN of being convert the different successive RR intervals in the frequency Fig. 2. This schematic shows the experimental design of the PN study.
Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200 domain. It is known that vagal and sympathetic activities affect low 3.2. Blood pressure and heart rate 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 shows the descriptive data of blood pressure and heart sympathovagal balance, and oscillations in very low frequencies rate. shows the results of 3-way ANOVA for blood pressure (VLF; 0.003e0.04 Hz) reflect the fluctuation of the vagal basoreflex and heart rate. The ANOVA indicated significant time-by- sensitivity in a steady state .
intervention interactions in systolic blood pressure (SBP) and dia-stolic blood pressure (DBP), but not in HR. There was no significantfinding in the main effects of time, group, and intervention. Post- 2.6. Statistical analysis hoc independent t-tests for the percent changes in the SBP andDBP following the 3-days PN intervention showed significant hy- Each biological and psychological measure was compared potensive effects for both SBP and DBP in the subgroup of active PN longitudinally (i.e., before and after the PN intervention) and cross- acupuncture (SBP: t sectionally (i.e., between HCs and patients with depression) using 40 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 sub- 3-way repeated measure analysis of variance (ANOVA) with "time" as a within-subject factor, and "intervention" (active vs. sham PN) DBP, 6.3% ± 6.8%) were significantly lower than those in the and "group" (HCs vs. depression) as the between-subject factors.
subgroup of sham PN (SBP, 0.9% ± 5.5%; DBP, 1.6% ± 9.5%). Of note, Post-hoc independent t-tests were performed for significant the active PN acupuncture induced hypotensive effects for both SBP ANOVA results. Next, we also performed analysis of covariance and DBP, however, these BP maintained the normal ranges in all (ANCOVA) model that incorporated age factor as covariate into the participants during and after the active PN intervention. On the same three-way ANOVA model for the analysis of cross-sectional other hand, no significant effect was observed in HR with active PN.
comparison between HC and depression groups (i.e., main effect Moreover, there were no significant correlations between age and of group), since we did not match age between both groups (group: the value of BP, HR, and these change by PN.
t40 ¼ 3.901, P < 0.0001). Further, Pearson's correlation analysiswas performed between the percent changes of each value for each 3.3. Autonomic function outcomes group (HC and depression) as well as subgroup (active and sham PNacupuncture). A conservative p-value (0.01) was used as a signifi- shows the descriptive data of autonomic functions.
cance level in this analysis. Statistical procedures were performed shows the results of 3-way ANOVA for each index of auto- using the SPSS software (SPSS Japan Inc., Tokyo, Japan).
nomic functions. The ANOVA for CVRR and CVI indicated a signif-icant time-by-intervention interaction and main effects of group with no significant main effects of time and intervention. However,the ANOVA for VLF showed a significant main effect of group with 3.1. Psychological outcomes no significant time-by-intervention interaction or main effect oftime. The ANOVA for CSI and LF/HF showed no significant time-by- contains descriptive data of the psychological tests.
intervention interactions or main effects of time, group, and shows the results of 3-way ANOVA for the psychological intervention. The ANCOVA that incorporated age factor as covariate tests. The 3-way ANOVA indicated a significant time-by- between the group of HCs and patients with depression indicated intervention interaction in the BDI-II and a main effect of group significant main effects of group in CVRR (F1, 37 ¼ 11.318, P ¼ 0.002), with no main effect of time. Further, significant main effects of CVI (F1, 37 ¼ 4.218, P ¼ 0.047), and VLF (F1, 37 ¼ 5.314, P ¼ 0.027) group in the state and trait of the STAI assessments were observed, whereas no significant main effects of group in CSI and LF/HF. The whereas no significant time-by-intervention interactions were independent t-tests for the percent changes in CVRR and CVI shown in the state and trait in the STAI assessments. Post-hoc in- following the 3-days PN intervention revealed that the percent dependent t-tests for the percent changes in the score of the BDI-II changes in CVRR and CVI in the subgroup of active PN acupuncture by the PN intervention showed a following significant result. In the (CVRR: 24.3% ± 26.6%, t40 ¼ 5.194, P < 0.0001; CVI: 6.2% ± 8.1%, subgroup of active PN acupuncture, the percent improvement of t40 ¼ 3.014, P ¼ 0.004) were significantly better than those in the the score in the BDI-II (34.3% ± 36.8%) was significantly better subgroup of sham PN intervention (CVRR: 10.7% ± 15.8%; (t40 ¼ 3.524, P ¼ 0.001) than those of the subgroup of sham PN CVI: 2.8% ± 11.0%). These results indicate that active PN acupuncture (5.7% ± 36.8%).
acupuncture can significantly improve the vagal function indexed Table 1Demographic 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.
Patients with depression Active PTN (N ¼ 6) Sham PTN (N ¼ 6) Active PTN (N ¼ 15) Sham PTN (N ¼ 15) *Significant findings in paired t-test between pre and post PTN acupuncture. (P < 0.05).

Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200 Table 2Results 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  intervention  group *Significant findings in the ANOVA (P < 0.05); bmp: beat per minute.
by CVRR and CVI. shows the scatter plots that demonstrate 3.4. Clinical correlations the PN-induced changes in BDI-II, SBP/DBP, and CVRR/CVI betweenthe subgroup of active and sham PN acupuncture. Further, post-hoc The correlation analysis was conducted between percent independent t-tests for CVRR, CVI, and VLF before and after the PN changes in the BDI-II, SBP, DBP, CVRR, and CVI, because these acupuncture demonstrated that the group of depression had indices showed significant changes following active PN acupunc- significantly worse values of CVRR (pretreatment: t40 ¼ 5.641, ture. There were significant correlations between the percent P < 0.0001; posttreatment: t40 ¼ 4.488, P < 0.0001), CVI (pre- changes in SBP and DBP (r ¼ 0.588, P ¼ 0.005, N ¼ 21) and the treatment: t40 ¼ 3.318, P ¼ 0.002; posttreatment: t40 ¼ 2.877, percent changes in CVRR and CVI (r ¼ 0.678, P ¼ 0.001, N ¼ 21).
P ¼ 0.006), and VLF (pretreatment: t40 ¼ 3.416, P ¼ 0.001; post- However, significant correlations were not observed among the treatment: t40 ¼ 3.994, P < 0.0001), compared to the group of HC.
percent changes in BDI-II scores, blood pressure (SBP and DBP), and That is, patients with depression had significantly lower vagal vagal nerve function (CVRR and CVI). In addition, subanalysis functions indexed by CVRR, CVI, and VLF, compared to HC.
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 inSBP 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 ReRinterval; DBP ¼ diastolic blood pressure; PN ¼ Press Needle; SBP ¼ systolic blood pressure.

Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200 the traits of STAI and VLF (r ¼ 0.615, P ¼ 0.003, N ¼ 21) in the confounding effect by applying the ANCOVA model that included subgroup of active PN acupuncture [However, no sig- age as covariate. As a result, we still observed significant main ef- nificant correlation was observed in the subgroup of sham PN.
fects of CVRR, CVI, and VLF in this comparison analysis between the Further, following the active PN acupuncture, there was a signifi- two groups. It means that patients with depression had worse vagal cant correlation between percent improvements in the state of the functions compared to HCs, even considering the confounding STAI assessment and CSI (r ¼ 0.646, P ¼ 0.009, N ¼ 15) in the group factors by age in this study.
of depression However, no significant correlation was Furthermore, as an important aspect in depression associated observed between the two in the subgroup of sham PN.
with vagal nerve function, consideration should be given to the sideeffects of antidepressants, because most antidepressants can 3.5. Adverse effects adversely affect the autonomic function , especially on vagalnerve function (i.e., values of CVRR and CVI decreased).
Adverse effects such as autonomic dysfunction, abnormal hy- However, practically it is very difficult to discontinue or taper the potension, and skin disorder were not observed with the inter- antidepressants in those inpatients with depression for the study to vention of PN acupuncture in the study.
exclude the influence of antidepressants on autonomic functions.
Therefore, in this study we applied a sham-controlled design to evaluate effects of active PN acupuncture on autonomic functions.
As a result, compared to sham PN, active PN acupuncture demon- 4.1. Study findings strated a significant improvement effect on vagal nerve function,which also partially correlated with the improvement of SAI score The present study generated several significant findings. First, ]. That is, our finding suggests that active PN acupuncture active PN acupuncture demonstrated a significant improvement on has a potential effect to improve vagal function surpassing the the BDI-II scores, a significant reduction on the SBP/DBP which remained within the normal range, and a significant improvement of vagal nervous function on the CVRR and CVI, compared to sham In this study, there was no significant correlation between the PN acupuncture. Second, we confirmed that patients with depres- improvement of BDI-II score and vagal nerve function measured sion exhibited significantly worse scores of the BDI-II, state and with ECG. Thus, we need to interpret the relationship between the trait of the STAI assessments, as well as significantly lower values in antidepressant effect and improvement of vagal function by the CVRR, CVI, and VLF. These latter results of autonomic functions acupuncture carefully. Although there is a limit in our findings, suggest vagal nervous dysfunction in patients with depression, as given the evidence of previous studies that suggesting the rela- reported in previous studies . Further, we did not observe a tionship among acupuncture, depression, and autonomic functions significant sympathetic inhibition measured with CSI following the biological rationale for the therapeutic effect of active PN acupuncture intervention, however, there was a clinical PN acupuncture, which may be associated with the improvement of correlation between improvement of anxiety symptoms in the vagal nerve function, could be explained from the following score of state in the STAI and sympathetic inhibition (i.e., decrease promising evidence (e.g., da Silva and Dorsher, 2014). To be specific, in value of CSI) in patients with depression. Therefore, it was for example, it is known that vagal nerve stimulation (VNS) therapy speculated that sympathetic inhibition may also play a role in the can cause an antidepressant effect in patients with treatment- therapeutic mechanism of acupuncture in depression. Moreover, resistant depression and induce a significant increase in significantly lower value of VLF in patients with depression may be CVRR by modulating the sympathovagal balance in the central related to dysfunctional homeostatic regulation of blood pressure, nervous system . Apparently, there is a large methodological since the VLF is considered to reflect the capacity of vagal basore- difference in their intervention between the acupuncture and VNS, flex sensitivity .
however, it is presumed that both treatments share a common It is well known that there is an aging effect on autonomic therapeutic mechanism for depression in terms of the neuro- function in a direction of worsening. In the cross-sectional analysis modulating effect on vagal nerve function . Thus, the between HCs and patients with depression, since age was not improvement of vagal nerve function may be associated with the matched between both groups, we tried to reconcile this underlying 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 Further, the hypotensive effect of the PN acupunc- ture within normal range may be induced by improving the imbalance of autonomic function primarily through the vagal sta- bilization modulated by active PN acupuncture e.
Although the 0.6 mm length of PN seems subtle acupuncture stimulation toward acupoints, the observed clear difference in HRV changes between active and sham PN suggests the validity of this non-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 of active PN acupuncture because we only performed biological and psychological assessments before and 3 days after the PN 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 a bottom-up neuromodulation. RCTs with large sample sizes are needed 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.
Y.N. and M.N. were involved in conception and design of the study. Y.N., T.I., Y.T., and M.N. recruited the participants and per- formed 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. inter- preted the results of study. Y.N. prepared figures and drafted the manuscript. Y.N. and M.N. edited and revised manuscript. All au- thors have approved final version of manuscript.
Conflict of interest statement All authors have no conflicts of interest to declare in this study.
We would like to thank Ms. Misa Inoue, Ms. Chiaki Osawa, Ms.
Yukari Sawada, Mr. Gen Ishii for their clinical support, and Seirin Co., Ltd for their technical advice. We also would like to appreciate Mr. Shirou Obata and Mr. Yasuhiro Ochi of MEDILINK Co., Ltd for their technical support.
Y. Noda et al. / Complementary Therapies in Clinical Practice 21 (2015) 193e200

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