Effects of transcranial direct current stimulation on pain, mood and serum endorphin

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Accepted Manuscript
Effects of transcranial direct current stimulation on pain, mood and serum endorphin
level in the treatment of fibromyalgia: A double blinded, randomized clinical trial
Eman M. Khedr, Eman A.H. Omran, Nadia M. Ismail, Dina H. El-Hammady, Samar
H. Goma, Hassan Kotb, Hannan Galal, Ayman M. Osman, Hannan S.M. Farghaly,
Ahmed A. Karim, Gehad A. Ahmed
PII: S1935-861X(17)30838-0
DOI: 10.1016/j.brs.2017.06.006
Reference: BRS 1073
To appear in: Brain Stimulation
Received Date: 6 January 2017
Revised Date: 27 April 2017
Accepted Date: 17 June 2017
Please cite this article as: Khedr EM, Omran EAH, Ismail NM, El-Hammady DH, Goma SH, Kotb
H, Galal H, Osman AM, Farghaly HSM, Karim AA, Ahmed GA, Effects of transcranial direct current
stimulation on pain, mood and serum endorphin level in the treatment of fibromyalgia: A double blinded,
randomized clinical trial, Brain Stimulation (2017), doi: 10.1016/j.brs.2017.06.006.
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Effects of transcranial direct current stimulation on pain, mood and serum endorphin 
level in the treatment of fibromyalgia: 
A double blinded, randomized clinical trial 
 
1Eman M. Khedr, 2Eman A. H. Omran, 2Nadia M. Ismail, 3Dina H. El-Hammady, 2Samar H. 
Goma, 4Hassan Kotb, 5Hannan Galal, 4Ayman M. Osman, 6Hannan S. M. Farghaly, 
8,9Ahmed A. Karim, 7Gehad A. Ahmed 
 
*Corresponding Author 
Prof. Dr. Eman M. Khedr 
Department of Neuropsychiatry, Faculty of Medicine 
Assiut University Hospital, Assiut, Egypt 
Head of the Neuropsychiatric Department, 
Faculty of Medicine, Aswan University Hospital 
Phone: +02-01005850632 
Fax: +02-088-2333327 
Email: emankhedr99@yahoo.com 
 
1Department of Neuropsychiatry, Faculty of Medicine, Assiut University, Assuit, Egypt. 
2Department of Rheumatology and Rehabilitation, Faculty of Medicine, Assiut University, 
Assiut, Egypt 
3Department of Rheumatology and Rehabilitation, Faculty of Medicine, Assiut University, 
Assiut, Egypt.3Department of Rheumatology and Rehabilitation, Faculty of Medicine, 
Helwan University. Cairo, Egypt. 
4Department of Anesthesia and Intensive Care, Faculty of Medicine, Assiut University, 
Assuit, Egypt. 
5Department of clinical pathology, Faculty of Medicine, Assuit university, Assuit, Egypt. 
6Department of Pharmacology, Faculty of Medicine, Assuit University, Assuit, Egypt. 
7Department of Rheumatology and Rehabilitation, Faculty of Medicine, Sohag University, 
Sohag, Egypt 
8Department of Psychiatry and Psychotherapy, Faculty of Medicine, University of Tübingen, 
Germany 
9Department of Prevention, Health Psychology and Neuro-rehabilitation, SRH University of 
Riedlingen, Riedlingen, Germany 
 
Word count: 2,866 
Key words: 
Fibromyalgia; direct current stimulation (tDCS), widespread pain index, Hamilton 
Depression and anxiety Rating Scale, pain sensitivity threshold, endorphin level. 
 
ClinicalTrials.gov Identifier: NCT02704611 
 
 
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ABSTRACT 
Background Recent studies have shown that novel neuro-modulating techniques can have 
pain-relieving effects in the treatment of chronic pain. The aim of this work is to evaluate the 
effects of transcranial direct current stimulation (tDCS) in relieving fibromyalgia pain and its 
relation with beta-endorphin changes. 
Material and Methods Forty eligible patients with primary fibromyalgia were randomized 
to receive real anodal tDCS or sham tDCS of the left motor cortex (M1) daily for 10 days. 
Each patient was evaluated using widespread pain index (WPI), symptom severity of 
fibromyalgia (SS), visual analogue scale (VAS), and determination of pain threshold as a 
primary outcome. Hamilton depression and anxiety scales (HAM-D and HAM-A) and 
estimation of serum beta-endorphin level pre and post-sessions were used as secondary 
outcome. All rating scales were conducted at the baseline, after the 5th, 10th session, 15 days 
and 1 month after the end of the sessions. 
Results Eighteen patients from each group completed the follow-up schedule with no 
significant difference between them regarding the duration of illness or the baseline scales. A 
significant TIME × GROUP interaction for each rating scale (WPI, SS, VAS, pain threshold, 
HAM-A, HAM-D) indicated that the effect of treatment differed in the two groups with 
higher improvement in the experimental scores of the patients in the real tDCS group (P = 
0.001 for WPI, SS, VAS, pain threshold, and 0.002, 0.03 for HAM-A, HAM-D respectively). 
Negative correlations between changes in serum beta-endorphin level and the changes in 
different rating scales were found (P = 0.003, 0.003, 0.05, 0.002, 0002 for WPI, SS, VAS, 
HAM-A, and HAM-D respectively). 
Conclusion Ten sessions of real tDCS over M1 can induce pain relief and mood 
improvement in patients with fibromyalgia, which were found to be related to changes in 
serum endorphin levels. 
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Key words: 
Fibromyalgia; direct current stimulation (tDCS), widespread pain index, Hamilton 
Depression and anxiety Rating Scale, pain sensitivity threshold, endorphin level. 
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INTRODUCTION 
Fibromyalgia syndrome (FMS) is a chronic painful, non-inflammatory condition 
characterized by a history of widespread pain, fatigue and diffuse tenderness on examination. 
The official definition of FMS, which is most commonly referred to, was published in 2010 
by the American College of Rheumatology (ACR)[1]. According to these new criteria, the 
most important diagnostic variables were the widespread pain index (WPI) and categorical 
scales for cognitive symptoms, un-refreshed sleep, fatigue, and a number of somatic 
symptoms. The categorical scales were summed to create symptom severity for fibromyalgia 
[1]. Approximately 6-20% of the population has FMS with peak prevalence ranging between 
25 and 55 years of age being higher in females than males [2]. 
In the past decade, a number of studies have revealed changes in brain activity associated 
with fibromyalgia. The pathophysiology of fibromyalgia is still unclear but appears to 
involve central nervous system dysregulation [3]. Panerai et al [4] identified lower 
concentrations of beta-endorphins in mononuclear cells of the peripheral blood in 
fibromyalgia patients. Harris et al [5] also found decreased mu-opioid receptor availability in 
the brains of fibromyalgia patients. However some studies that compared peptide 
concentrations in fibromyalgia and control groups found no differences in blood plasma [6, 
7]. Younger et al [8] also found no evidence found for abnormal endogenous opioid activity 
in women with fibromyalgia. 
Ceko and colleagues [9] explored structural and fMRI changes in young FMS patients, and 
found a decoupling between the insula and anterior mid-cingulate cortex, two brain regions 
that are normally strongly connected in healthy adults, as part of a salience network. Proton 
magnetic resonance spectroscopy (1H-MRS) is a non-invasive MRI technique that can 
quantify the concentration of multiple metabolites within the humanbrain. Harris et al [10] 
used 1H-MRS to study glutamate and Glx (combined glutamate and glutamine) levels 
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specifically in patients with chronic ‘centralized’ pain. Subsequently, they compared 
glutamate and Glx levels within the posterior insula between FM patients and pain-free 
controls and found significantly elevated levels of these molecules in the FM patients [10]. 
Findings of elevated Glx within the FM brain have also been reported in the amygdala [11], 
the posterior cingulate [12], and the ventral lateral prefrontal cortex [13]of individuals with 
FM. Finally, changes in blood flow in the thalamus, caudate nucleus, and pontine tegmentum 
detected by single-photon–emission computed tomography (PET) have been observed [14]. 
These findings have encouraged researchers to evaluate the effect of neuro-modulating 
techniques in the relief of this type of chronic pain in order to reverse the maladaptive 
plasticity in central neural circuits. A recent review noted that many studies in other pain 
syndromes reported increased activation in M1, which had an increased response to 
nociceptive sensory stimuli [15]. Thus M1 has been a favorite target of neuromodulatory 
approaches. 
Two relatively new forms of neuromodulatory treatment are transcranial direct current 
stimulation (tDCS) and transcranial magnetic stimulation (TMS). Studies using anodal tDCS 
of M1 have applied stimulation either to the hemisphere contralateral to pain (in case of focal 
or lateralized pain) or the dominant (left) hemisphere (in case of more diffuse pain) [16]. 
Anodal tDCS has been shown to increase cortical excitability, which is postulated to mitigate 
pain symptoms through indirect effects on pain processing regions in the brain [17], M1 
tDCS may reduce pain by activating various neural circuits present in the precentral gyrus, 
which would be afferents or efferents that connect structures involved in sensory or 
emotional component of pain processing, such as the thalamus or the DLPFC, or by 
facilitating descending pain inhibitory controls [18]. Patients with central refractory pain have 
also shown improvements of around 40-80% following M1 stimulation with epidural 
electrodes or with transcranial magnetic stimulation (TMS) [19-21]. 
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Clinical trials investigating the effects of tDCS over M1 have reported variable 
amounts of pain reduction in fibromyalgia [17, 22, 23], and a recent review found no 
significant difference between sham and real M1 tDCS on short-term pain relief [24]. The 
lack of consistent effects may be due to significant heterogeneity between the included 
studies (i.e., stimulation parameters, number of treatment sessions, type of chronic pain). In 
the present study we have tried to provide additional insight into the effects of anodal tDCS 
of the left M1 by studying both its effects on relieving pain and its relation to beta-endorphin 
levels. 
METHODS 
This study was conducted at the Assiut University Hospital during the period from October 
2015 to April 2016. All patients with primary fibromyalgia were recruited according to the 
2010 American College of Rheumatology Criteria (ACR)[1]. Fibromyalgia is characterized 
primarily by diffuse musculoskeletal pain, mechanical allodynia, and hyperesthesia [25]. 
The most important diagnostic variables are WPI and categorical scales for cognitive 
symptoms, un-refreshed sleep, fatigue, and a number of somatic symptoms. The categorical 
scales were summed to create SS scale value from 0 to 12, with WPI >7 and a symptom 
severity scale (SS) >5 or WPI 3-6 and SS >9 [1]. 
All FM patients presented to the hospital fulfilling the below criteria were invited to 
participate. We included FM patients who reported a mean pain score ≥ 4 on a 10-point 
visual analog scale (VAS) during the two weeks preceding the clinical trial. Only patients 
who consent for participation and from nearby districts were recruited to ensure easiness of 
the follow-up. We excluded patients with a history of coexisting autoimmune or chronic 
inflammatory disease (i.e. Rheumatoid arthritis, systemic lupus erythematosus or 
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inflammatory bowel disease), past or present history of substance abuse, neuropsychiatric 
disorders, (major depression and schizophrenia), pregnant and lactating women. 
Sixty patients with primary fibromyalgia were recruited from outpatient clinic in this 
study. Twenty cases didn’t meet inclusion criteria and were therefore excluded: 10 of them 
had systemic diseases. Another 6 cases had neuropathic pain and 4 cases had psychiatric 
disorders. Forty cases were allocated into one of the two groups (1:1 ratio) real tDCS group 
and sham tDCS group. Two cases from each group didn't complete the follow up and the 
remaining 18 cases in each group completed the study (Figure 1). 
Figure 1 
Assiut Medical School Ethical Review Board approved the study. Written informed 
consent was obtained from all of the subjects after describing the nature of the intervention 
and the possibility of receiving sham stimulation. 
All eligible participants who accepted to participate in the study were submitted to the 
following rating scales before treatment: WPI and SS for FM[1], and VAS for pain severity. 
Depression and anxiety were assessed using Hamilton depression and Hamilton anxiety 
scales (HAM-D and HAM-A)[26, 27]. Additionally, the pain threshold for each patient was 
determined. 
Mechanical pain sensitivity threshold 
To detect the pain threshold we used Electronic model of Von Frey unit (EVF4) that 
combines ease-of-use and rapidity for the determination of the mechanical sensitivity 
threshold. Skin sensory testing with punctate stimuli was performed by the von Frey 
technique using the von Frey electronic device (BIO-CIS software automatically records the 
results on a PC through a RS 232 port), with a constant slope of increasing punctate pressure 
up to the detection of mechanical pain threshold (MPT) [28]. The mean of three 
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measurements was taken as the pain threshold (MPT), which is defined as the lowest pressure 
that produced a sensation of pain. 
Assessment of serum beta-endorphin (human β-EP) level 
The blood samples were withdrawn from all studied patients. Serum was separated from all 
samples. Two samples (4 ml of blood for each) were withdrawn: the first sample was taken 
before the 1st session; the second sample was taken one hour after the end of the 10th tDCS 
session. The samples were left at room temperature for 10–20 min, centrifuged for 20 min at 
the speed of 2000–3000 rpm, and then the serum was removed and stored at −20 °C until the 
beginning of the analyses. Human β-EP ELISA kit was used in the measurement of human β-
EP concentrations in serum. No significant cross-reactivity or interference between human β-
EP and analogues were observed. 
These ELISA kits used competitive-ELISA as the method. The microtitre plate 
provided in these kits had been pre-coated with β-EP. During the reaction, β-EP in the sample 
or standard competed with the affixed amount of β-EP on the solid phase supporter for sites 
on the Biotinylated Detection Ab specific to β-EP. The enzyme-substrate reaction was 
terminated by the addition of a sulphuric acid solution and the color change was measured 
spectrophotometrically at a wavelength of 450 nm ± 2 nm. The concentration of β-EP in the 
samples was then determined by comparingthe samples to the standard curve. 
Randomization 
All eligible participants were randomly assigned to one of the two groups. Allocation 
concealment was done using serially numbered closed, opaque envelopes. Each patient was 
given a serial number from a computer generated randomization table, and was placed in the 
appropriate group after opening the corresponding sealed envelope. Counseling for 
participation was conducted before recruitment. 
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The experimental group received real tDCS with the following parameters: 2 mA for 20 
minutes on 5 consecutive days/week for 2 weeks. The anodal electrode (size: 24 cm² with a 
current density of 0.08 mA was placed over the left primary motor area (15 s ramp in and 15 
s ramp out). To stimulate the M1, the anodal electrode was placed over C3, according to the 
international 10–20 EEG system [29]. 
 The reference electrode (size: 24 cm²) was fixed over the contralateral arm (extra-cephalic). 
We used an extracephalic reference avoids the confounding effects of two electrodes with 
opposite polarities over the brain [13, 30]. Khedr et al [31] showed that; reduction of 
postsurgical opioid consumption and pain relief in total knee arthroplasty after 4 sessions of 
tDCS over M1 even when the cathode is placed over an extra-cephalic site on the shoulder 
[31]. 
The control group received sham tDCS using the above-described parameters as in the 
experimental group; however, sham current was applied for only 30 seconds at the beginning 
and at the end of the session. A 30 second application of current is considered to be a reliable 
method of sham stimulation as sensations arising from tDCS treatment occur mostly at the 
beginning and at the end of the application. Individual measurements determined the 
anatomical location for placement of the electrodes at C3 using the EEG 10/20 system. The 
investigator responsible for delivering tDCS had no contact with the patients, ensuring a 
double-blind procedure. 
Follow-up procedure 
An evaluator who was blinded to the stimulation protocol followed up all study participants. 
They were asked to report side effects and any inconvenience during or after the procedure. 
The following scales were reassessed: WPI, SS, VAS, and Pain thresholds were 
determined at the post 5th session, post 10th session, 2 weeks after the end of sessions and one 
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month later as primary outcome. HAM-D, and HAM-A were measured at the same time of 
the previous scales, as well as the blood sample was obtained by the end of the treatment to 
compare serum endorphins levels with the values obtained before the treatment as secondary 
outcome. 
Data collection and analysis: 
The data was collected and entered on Microsoft access database to be analyzed using the 
Statistical Package for Social Science (SPSS Inc., Chicago, version 19). The values for each 
scale were analyzed separately by one-way repeated measures analysis of variance 
(ANOVA). Two-way ANOVA were used to assess the interaction between groups (Time 
‘pre, 5th, 10th, 15 days after stimulation and after 1 month’ × Group ‘real & sham’). Post-hoc 
t-tests were used to assess the interaction between groups at different points of assessment. 
The Greenhouse–Geissner correction of degrees of freedom was used when necessary 
to correct for non-sphericity of the data. The percentage of reduction in each scale was 
calculated after the 10th, 15 days, one month after the end of stimulation according to the 
following formula: 
Percentage of reduction= (pre-stimulation score −Post-stimulation score) × 100)/pre-
stimulation score) 
Comparisons between the two groups were conducted using the Mann-Whitney test. 
RESULTS 
The mean age of the patients was 31.3 ± 10.9 years in the experimental group, (seventeen 
females and one male) with mean illness duration 6.1 ± 2.7 months, while it was 33.9 ± 11.2 
years in the sham group (seventeen females and one male) with a mean illness duration of 
6.1± 2.5. 
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Table 1 shows the baseline demographic and clinical criteria of the two study groups. 
There were no significant differences between groups regarding age, sex, duration of illness, 
WPI, SS, VAS, HAM-D, HAM-A scores and pain sensitivity thresholds. All patients 
tolerated tDCS well. The only adverse effects were itching and redness of skin in 3 cases 
from the experimental group. 
 
Table 2 shows the mean and SD of each pain rating scale at each time point. Pain ratings 
decreased over time in both the experimental and the sham group. Thus, a one-way ANOVA 
on the data from each group separately revealed a significant effect of TIME (pre, after the 
5th, 10thsession, and 15 days after the end of the session and one month later) in both groups 
on all rating scales (see Table 2). However, the effects were significantly larger with real 
stimulation compared with sham stimulation. Two-way ANOVA with TIME and GROUP 
(real or sham) as main factors showed a significant TIME × GROUP interaction for each 
rating scale. This indicates that the effect of treatment differed in the two groups with higher 
improvement in the experimental group. These data are illustrated in figure 2 indicating the 
results of post hoc t-tests between the experimental and the sham group at each time point. 
 
Insert Figure 2 here 
Insert Figure 3 here 
 
The effect of tDCS on HAM-D and HAM-A are summarized in table 3 and figure 3&4. 
Concerning the pain-rating scales, there were also significant improvements in both groups. 
However, the significant interaction between groups in the two-way ANOVA (p=0.03 for 
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HAM-D scale and p= 0.002 for HAM-A) confirms that the improvement was larger in the 
experimental group compared with the sham group. 
There was no significant difference at baseline between levels of serum beta-endorphin in the 
two groups (p= 0.302). Beta-endorphin levels increased significantly in both groups after 
treatment (experimental group: from 223.2 ± 120.6 ng/ml pre-stimulation to 263.3 ±150.9 
ng/ml in the last assessment point, P= 0.001, T= - 3.9; sham group: 188.5 ± 71.2 ng/ml to 
207.4 ± 79.3 ng/ml with P= 0.002, T= - 3.8). The change in the experimental group tended to 
be greater than in the sham group, but this was of borderline significance (experimental 
group: post- pre = 40.0±43.1ng/ml; sham group: 18.9±21.3 ng/ml; T= 1.8, P= 0.07). 
Insert Figure 4 here 
Insert Figure 5 here 
Moreover, significant negative correlations were observed between change in serum beta-
endorphin level and WPI, SS, and VAS (r= - 0.47, P= 0.003, r= - 0.48, P=0.003, and r= - 
0.34, P=0.05, respectively). There were also significant negative correlations between change 
in serum beta-endorphin level and HAM-D, and HAM-A (r= - 0.49, P= 0.002, and r= - 0.5, 
P= 0.002; respectively, cf. Table 4 and Figure 5e and 5f). 
Positive correlations were observed between serum endorphin and pain threshold with r= 
0.61, P= 0.001 (see table 4 and figure 5a, b, c, d). 
DISCUSSION 
This study demonstrates that a real tDCS protocol, applying our stimulation parameters, is 
more effective in relieving pain than sham tDCS in patients with FM with cumulative and 
long-term effects. About 39.0% pain reduction was observed in the experimental group by 
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the end of treatment and 40-49% over the following2 weeks. Remarkably, a parallel 
improvement in depression level and endorphin were also observed. 
Previous work has shown that both invasive motor cortical stimulation as well as non-
invasive rTMS in lateralized pain syndromes, leads to a significant anti-nociceptive effect 
[19, 20]. It is thought that modulation of M1activates superficial layers of the motor cortex 
(intercortical interneurons, rather than corticospinal axons), which leads to a cascade of 
synaptic events resulting in modulation of activity in an extensive neural network including 
thalamic nuclei, limbic system, brainstem nuclei and spinal cord. These regions are 
considered to be critical areas of the pain matrix. Several studies have shown that rTMS of 
the M1 has analgesic effects in fibromyalgia [32, 33]. Also tDCS may interfere with 
functional connectivity, synchronization, and oscillatory activities in various cortical and 
subcortical networks. This has been shown for tDCS delivered to M1 [34-36]. 
Chronic pain and depression are each prevalent and often co-occur [37]. Rayner et al 
[38]found that the prevalence of depression among patients with chronic pain was 60.8% and 
33.8% met the threshold for severe depression. The relationship between depression and pain 
is of significant interest in FM and other similar chronic pain disorders. When rigorous 
criteria are applied to diagnose depression, the prevalence of depression and concurrent 
chronic pain varies from 30–54%. Since fibromyalgic pain and depression frequently co-
exist, it was interesting that we found a significant correlation between the change in pain 
rating scores and change in HAM-D and A scores. The analgesic effects of M1 stimulation 
might induce functional changes in thalamic and subthalamic nuclei and modulate the 
affective component of pain [39, 40]. Another possible explanation of the improvement in 
mood is the spread of the effect of tDCS over the M1 to the left dorsolateral prefrontal cortex, 
which is a well-known cortical target to treat depression. The tDCS of M1 can alter the 
functional connectivity (FC) of regions under the stimulating electrode as well as spatially 
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distant but structurally connected regions, such as the thalamus [36] and the dorsolateral 
prefrontal cortex [41, 42]. 
Previous studies found that endogenous opioids may play a role in NBS-induced 
(motor cortical stimulation and rTMS) analgesia [43, 44]. De Andrade et al [45] confirmed 
that the endogenous opioids systems (EOS) are involved in the analgesic effects induced by 
rTMS of M1. These physiological changes are also associated with the after-effects of non-
invasive brain stimulation. Real tDCS also acts on the endogenous opioid system similarly to 
rTMS [46]. In the present study, the significant correlation between the change in serum 
endorphin levels and the changes in different rating scores after tDCS sessions may confirm 
that the increase beta endorphin after tDCS stimulation is associated with the pain relief and 
the improvement of depression and anxiety and opioid system is involved in FM. The opioid 
system plays a key role in mediating analgesia and social attachment and may also affect 
depression given the link between β-endorphins and depression symptoms [47, 48]. To date, 
β-endorphin secretion has been used for the diagnosis of depression and it could be used as 
an agent in a therapeutic strategy [49] . According to the above results, the improvement in 
different scales (pain and mood) may be related to the release of β-endorphin via tDCS. As 
tDCS is cheaper and has fewer potential side effects than rTMS, and in many studies appears 
to have a similar clinical effect. This trial suggests that the similarities also may include 
effects on endorphin levels. 
It should also be noted that the sham group reported significant improvement in most 
of the rating scales. This may be because sham tDCS produces a significant placebo response. 
Consistent with previous work implicating the endogenous opioid system in placebo 
analgesia was recorded [50, 51]. It has recently been shown that sham tDCS causes the 
release of endogenous opioids in the periaqueductal gray (PAG), precuneus, and thalamus 
[46]. Our results were consistent with this experiment as the serum endorphin level was also 
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increased immediately after sham stimulation. However, although of borderline significance, 
the rise in endorphin levels was greater (almost double) in the tDCS group compared with 
sham. Thus we think that there may be a threshold level above which endorphin levels must 
change in order to have a measureable effect on symptoms. Further multicenter studies are 
needed to confirm the obtained effects with our stimulations parameters. Our results can be 
used to calculate the required sample size for future multicenter studies. Future studies could 
also include neuropsychological parameters, which have previously shown to be modulated 
by tDCS [52, 53] 
In conclusion ten sessions of real tDCS over M1 can induce pain relief and mood 
improvement in patients with fibromyalgia and it could be related partially to the modulation 
of serum endorphin level. 
Conflict of Interest: 
The authors declare no conflict of interest 
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 Figure Legends 
 
Figure 1: Flow chart of the patients through the course of the study. 
Figure 2: Effects of tDCS on WPI (panel 2a), SS (panel 2b), VAS (panel 2c) and pain 
thresholds (panel 2d) of primary fibromyalgia among the studied groups. 
Figure 3: Effect of tDCS on HAM-D and HAM-A among the studied groups 
Figure 4: Spearman correlation between change in widespread pain index score (pre-post 
10th session) and the change in HAM-A (figure 4a) and HAM-D scales (figure 4b). 
Figure 5: Correlation between the change of serum beta endorphin level (post 10th —pre-
session) and Wide spread index (Fig 5a), Symptoms severity (Fig 5b), VAS score (Fig 5c), 
and pain sensitivity threshold (Fig 5d), post 10th –pre--session 
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Table 1: Demographic and baseline assessments of the patients among the studied groups. 
 
 Real group 
(mean ± SD) 
Sham group 
(mean ± SD) 
p-value 
Age 31.3 ± 10.99 33.89 ± 11.18 0.49 
Duration of illness(months) 6.1 ± 2.65 6.05 ± 2.53 1.00 
Sex F/M ratio 17/1 17/1 0.15 
Widespread pain index (WPI) 12.72 ± 3.51 11.44±3.59 0.29 
Symptom severity (SS) scale 12.72 ± 3.51 7.78 ±1.003 0.81 
Visual analogue scale (VAS) 7.44 ±1.04 8.00 ± 0.84 0.09 
Hamilton Depression Scale 
(HAM-D) 
17.50 ± 4.42 18.28 ± 3.16 0.08 
Hamilton anxiety scale (HAM-A) 19.33 ± 4.51 18.72± 3.27 0.65 
Pain sensitivity threshold 196.26 ± 67.37 167.58±40.07 0.13 
SD: standard deviation. 
 
 
 
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Table 2:The effect of tDCS on different rating scales for pain and mood among the studied 
groups along the study period 
 
 Pre-session Post 5th session Post 10th session Two weeks 
after the last 
session 
One month later ANOVA Repeated measure 
analysis (each group separately) 
WPI 
Real 
Sham 
 
12.7±3.5 
11.4±3.6 
 
9.8±3.3 
11.0±3.4 
 
7.7± 3.5 
10.5± 3.1 
 
7.1± 3.7 
11.6± 3.6 
 
6.4±4.1 
11.7±3.1 
 
Df = 2.2, F= 17.9, P= 0.001 
Df= 3.1, F= 4.3, P= 0.008 
Interaction Time X Groups Df = 2.4, F= 16.36, P= 0.001 
SS 
Real 
sham 
 
7.7 ±1.6 
7.8 ±1.0 
 
6.06 ±1.8 
7.28 ± 0.9 
 
4.5 ± 1.5 
6.9 ±1.1 
 
4.8 ±2.3 
7.1 ± 1.3 
 
4.4± 2.3 
7.5± 1.7 
 
Df = 2.5, F= 13.8, P=0.001 
Df= 3.1, F= 3.1, P= 0.03 
Interaction Time X Groups Df = 2.7, F= 8.0, P= 0.001 
VAS 
 Real 
Sham 
 
7.4 ±1.1 
8.0 ± 0.8 
 
5.8 ±1.1 
7.2 ± 0.9 
 
4.6 ± 1.3 
6.6 ± 0.8 
 
4.4 ± 1.6 
6.9 ± 0.8 
 
3.9 ±2.1 
7.3± 0.9 
 
Df= 2.4, F= 28.3, P= 0.001 
Df= 3.2, F= 12.8, P= 0.001 
Interaction Time X Groups Df = 2.64, F= 12.66, P= 0.001 
Pain sensitivity threshold 
Real 
Sham 
 
196.5± 67.4 
167.6±40.1 
 
295.2±72.0 
179.7 ±40.9 
 
342.2 ±66.2 
214.3±33.8 
 
347.3±70.3 
203.02±37.3 
 
334.2 ± 82.9 
179.4 ±33.1 
 
Df= 3.1, F= 34.3, P= 0.001 
Df= 2.3, F= 9.85, P= 0.001 
Interaction Time X Groups Df = 3.09, F= 17.26, P= 0.001 
HAM-A 
Real 
Sham 
 
19.3 ±4.5 
18.7± 3.3 
 
14.4±5.0 
17.6± 3.5 
 
11.5 ± 4.7 
17.4 ±3.6 
 
12.6±5.9 
16.4 ±4.0 
 
11.6 ±5.9 
17.1 ±4.2 
 
Df = 2.6, F= 11.0, P= 0.001 
Df= 2.5, F= 3.9, P= 0.02 
Interaction Time X Groups Df = 2.6, F= 5.89, P= 0.002 
HAM-D 
Real 
Sham 
 
17.5 ± 4.4 
20.3 ± 3.2 
 
14.1± 4.5 
17.9 ± 3.2 
 
10.7±3.7 
17.7 ± 3.4 
 
11.4±5.7 
16.4 ±3.4 
 
10.6 ± 6.3 
17.6±4.0 
 
Df = 2.0, F= 12.5,P= 0.001 
Df= 2.5, F= 6.3,P= 0.002 
Interaction Time X Groups Df = 2.3, F= 3.4, P= 0.03 
 
 
WPI: wide spread pain index, SS: symptoms severity of fibromyalgia, VAS: Visual analogue scale, HAM-D Hamilton Depression Rating 
Scale, HAM-A: Hamilton anxiety 
Rating scale 
 
 
 
 
Table 3: Comparison between different parameters of fibromyalgia from before to after 
treatment 
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 # meaning deterioration of the score; WPI: wide spread pain index, SS: symptoms severity of fibromyalgia, VAS: Visual analogue scale, 
HAM-D: Hamilton Depression Rating Scale, HAM-A: Hamilton anxiety Rating scale 
 
 
 
 
 
 
 
Independen
t Samples 
Test 
Last 
assessment 
point (sham) 
Last 
assessment 
point 
(Real) 
Independent 
Samples Test 
Post 10th 
session 
(sham) 
Post10th 
session 
(Real) 
 
P= 0.001 
T= 5.931 
-3.3 ±11.9# 
0(0%) 
46.9±33.9 
8(44.44%) 
P= 0.001 
T= 5.553 
7.1 ±12.1 
0(0%) 
39.4±21.6 
8(44.4%) 
WPI (mean + SD percent of improvement) 
Number and percentage of patients ≥ 50% 
improvement 
P=0.001 
T= 4.363 
4.3±16.9 
0(0%) 
40.6±30.9
 
7(38.88%) 
P= 0.001 
T= 5.294 
10.4 ±10.2 
0(0%) 
39.9 ±21.3 
7(38.88%) 
SS(mean ± SD percent of improvement) 
Number and percentage of patients ≥ 50% 
improvement 
P=0.001 
T= 5.283 
7.7±13.6 
0(0%) 
46.3±27.9 
10(55.55%) 
P= 0.001 
T= 4.7 
17.02±8.8 
0(0%) 
38.4 ±17.1 
5(27.77%) 
VAS(mean ± SD percent of improvement) 
Number and percentage of patients ≥ 50% 
improvement 
P= 0.003 
T= 3.224 
12.7±17.7 
0(0%) 
39.6±30.7 
8(44.44%) 
P= 0.001 
T= 5.2 
-12.1±15.3# 
1(5.55%) 
37.7±14.2 
3(16.7%) 
HAM-D(mean ± SD percent of improvement) 
Number and percentage of patients ≥ 50% 
improvement 
P= 0.002 
T= 3.410 
8.9±15.4 
0(0%) 
37.3±31.9
 
6(33.33%) 
P= 0.001 
T= 5.519 
-6.6±11.4# 
0(0%) 
38.8±21.9 
(27.77%) 
HAM-A(mean ± SD percent of improvement) 
Number and percentage of patients ≥ 50% 
improvement 
P=0.001 
T=4.524 
11.3± 28.0 
2(11.11%) 
91.7± 69.9 
13(72.22%) 
P= 0.002 
T=3.451 
32.4± 27.3 
5(27.77%) 
92.4± 68.6 
12(66.66%) 
Pain sensitivity threshold (mean ± SD percent 
of improvement) 
Number and percentage of patients ≥ 50% 
improvement 
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Table 4: between changes in serum endorphin level pre and post 10th- pre sessions) and the 
changes in different rating scores (post 10th– pre-session) 
 
 WPI (post 
10th - pre 
session) 
SS-Score 
(post 10th- 
pre session) 
VAS 
(post 10th - 
pre session) 
Pain threshold 
(post 10th- 
pre session) 
HAM-D 
(post 10th - 
pre session) 
HAM-A 
(post 10th- 
pre session) 
Difference 
Serum β-
Endorphin level 
(post 10th - 
pre-session) 
P= 0.003R= -0.47 
P= 0.003 
R= -0.481 
P=0.05 
R= - 0.34 
 
P=0.001 
R= 0.643 
P= 0.002 
R= - 0.49 
P= 0.002 
R= - 0.50 
 
 
 
 
 
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Figure 1 
 
Potential participants screened(n=60) 
Randomized 
(n=40) 
Excluded (n=20) 
Didn’t meet inclusion 
criteria 
Associated with systemic 
diseases (n=10). 
Associated with 
neuropathic pain and 
neuropsychiatric (n=10) 
disorders (n=7). 
Sham group 
Withdrew after 5th 
session: unwell 
(n=2) 
Real group 
Withdrew after 10th session: 
unwell (n=1). 
Withdrew after 3rd 
session:difficulty travelling 
to come (n=1) 
Follow up visits 
Pre assessment, post 5thand post 
10th sessions, then after one and 2 
months of 1st assessment 
Sham 
group20patie
nts 
Real group 
20 patients 
Sham group 
18 patients 
completedthe study 
 
Real group 
18 patients 
completed the study 
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Figure 2 
 
 
 
 
 
 
 
 
 
 
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Figure 3 
 
 
 
 
Figure 4 
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Figure 5 
 
 
 
 
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 Figure Legends 
 
Figure 1: Flow chart of the patients through the course of the study. 
Figure 2: Effects of tDCS on WPI (panel 2a), SS (panel 2b), VAS (panel 2c) and pain 
thresholds (panel 2d) of primary fibromyalgia among the studied groups. 
Figure 3: Effect of tDCS on HAM-D and HAM-A among the studied groups 
Figure 4: Spearman correlation between change in widespread pain index score (pre-post 
10th session) and the change in HAM-A (figure 4a) and HAM-D scales (figure 4b). 
Figure 5: Correlation between the change of serum beta endorphin level (post 10th —pre-
session) and Widespeard index (Fig 5a), Symptoms severity (Fig 5b), VAS score (Fig 5c), 
and pain sensitivity threshold(Fig 5d), post 10th –pre--session 
 
 
 
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HIGHLIGHTS 
 
 
 
 
 
1- Ten sessions of real tDCS over M1 can induce pain relief and mood 
improvement in patients with fibromyalgia. 
2- Changes in serum beta-endorphin level correlated will with the 
changes in different rating scales of pain and Mood. 
3- Pain relief after tDCS could be related to endorphin release