Effects of yoga versus walking on mood, anxiety, and brain GABA levels: a randomized controlled MRS study.

Abstract

Yoga and exercise have beneficial effects on mood and anxiety. γ-Aminobutyric acid (GABA)-ergic activity is reduced in mood and anxiety disorders. The practice of yoga postures is associated with increased brain GABA levels. This study addresses the question of whether changes in mood, anxiety, and GABA levels are specific to yoga or related to physical activity.
Healthy subjects with no significant medical/psychiatric disorders were randomized to yoga or a metabolically matched walking intervention for 60 minutes 3 times a week for 12 weeks. Mood and anxiety scales were taken at weeks 0, 4, 8, 12, and before each magnetic resonance spectroscopy scan. Scan 1 was at baseline. Scan 2, obtained after the 12-week intervention, was followed by a 60-minute yoga or walking intervention, which was immediately followed by Scan 3.
The yoga subjects (n = 19) reported greater improvement in mood and greater decreases in anxiety than the walking group (n = 15). There were positive correlations between improved mood and decreased anxiety and thalamic GABA levels. The yoga group had positive correlations between changes in mood scales and changes in GABA levels.
The 12-week yoga intervention was associated with greater improvements in mood and anxiety than a metabolically matched walking exercise. This is the first study to demonstrate that increased thalamic GABA levels are associated with improved mood and decreased anxiety. It is also the first time that a behavioral intervention (i.e., yoga postures) has been associated with a positive correlation between acute increases in thalamic GABA levels and improvements in mood and anxiety scales. Given that pharmacologic agents that increase the activity of the GABA system are prescribed to improve mood and decrease anxiety, the reported correlations are in the expected direction. The possible role of GABA in mediating the beneficial effects of yoga on mood and anxiety warrants further study.

Full text

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Original Article
Effects of Yoga Versus Walking on Mood,
Anxiety, and Brain GABA Levels:
A Randomized Controlled MRS Study
Chris C. Streeter, MD,1Theodore H. Whitfield, ScD,2Liz Owen, BArch,3Tasha Rein, BA,1
Surya K. Karri, MD, MPH,4Aleksandra Yakhkind, MS,5Ruth Perlmutter, MA,6Andrew Prescot, PhD,7
Perry F. Renshaw, MD, PhD,8Domenic A. Ciraulo, MD,1and J. Eric Jensen, PhD9
Abstract
Objectives: Yoga and exercise have beneficial effects on mood and anxiety. g-Aminobutyric acid (GABA)-ergic
activity is reduced in mood and anxiety disorders. The practice of yoga postures is associated with increased
brain GABA levels. This study addresses the question of whether changes in mood, anxiety, and GABA levels
are specific to yoga or related to physical activity.
Methods: Healthy subjects with no significant medical/psychiatric disorders were randomized to yoga or a
metabolically matched walking intervention for 60 minutes 3 times a week for 12 weeks. Mood and anxiety
scales were taken at weeks 0, 4, 8, 12, and before each magnetic resonance spectroscopy scan. Scan 1 was at
baseline. Scan 2, obtained after the 12-week intervention, was followed by a 60-minute yoga or walking inter-
vention, which was immediately followed by Scan 3.
Results: The yoga subjects (n¼19) reported greater improvement in mood and greater decreases in anxiety than
the walking group (n¼15). There were positive correlations between improved mood and decreased anxiety
and thalamic GABA levels. The yoga group had positive correlations between changes in mood scales and
changes in GABA levels.
Conclusions: The 12-week yoga intervention was associated with greater improvements in mood and anxiety
than a metabolically matched walking exercise. This is the first study to demonstrate that increased thalamic
GABA levels are associated with improved mood and decreased anxiety. It is also the first time that a behavioral
intervention (i.e., yoga postures) has been associated with a positive correlation between acute increases in
thalamic GABA levels and improvements in mood and anxiety scales. Given that pharmacologic agents that
increase the activity of the GABA system are prescribed to improve mood and decrease anxiety, the reported
correlations are in the expected direction. The possible role of GABA in mediating the beneficial effects of yoga
on mood and anxiety warrants further study.
Introduction
Y
g-aminobutyricacid(GABA) systemshas beenfound inmood
disorders, anxiety disorders, and epilepsy.4–6All three of
these conditions respond to pharmacologic agents known to
oga has been used to reduce symptoms of depres-
sion, anxiety, and epilepsy.1–3Reduced activity in
increase GABA system activity, raising the possibility that
some of the therapeutic effect may be via increased GABA
activity.7In a previous study using magnetic resonance
spectroscopy (MRS) to obtain brain GABA levels, our group
demonstrated that experienced yoga practitioners had a sig-
nificant (27%) increase in whole-slab GABA levels after a 60-
minute session of yoga postures compared to no change in
1Division of Psychiatry, Boston University School of Medicine, Boston, MA.
2Division of Actuarial Science, Boston University, Boston, MA.
3Liz Owen Yoga, Arlington, MA.
4Department of Neurosurgery, Harvard University, Boston, MA.
5Medicine/Hematology-Oncology, Children’s Hospital Boston, Boston, MA.
6School of Medicine, University of Massachusetts, Boston, MA.
7Departments of Radiology and8Psychiatry, University of Utah, Salt Lake City, UT.
9Department of Psychiatry, Harvard University, Belmont, MA.
This article was previously presented as a poster at the American Psychiatric Association Annual Meeting, San Francisco, CA in 2008.
THE JOURNAL OF ALTERNATIVE AND COMPLEMENTARY MEDICINE
Volume 16, Number 11, 2010, pp. 1–8
ª Mary Ann Liebert, Inc.
DOI: 10.1089/acm.2010.0007
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GABA levels in controls after a 60-minute reading session.8
These findings raise the question of whether the associated
increase in GABA levels was specific to yoga or related to
physical activity in general.
There is a large body of research on the beneficial effects of
exercise on depression and anxiety.2,9,10The results of exer-
cise as a treatment for mild to moderate depression compare
favorably to psychotherapy and pharmacologic treatment,
supporting the contention that a behavioral intervention can
have an effect similar to a pharmacologic intervention on
mood.11
This study extends the findings of self-reported mood
changes by exploring a possible mechanism: changes in
thalamic GABA levels measured on MRS. This study was
designed to correlate changes in mood, anxiety, and brain
GABA levels, and to determine whether such changes are
specific to a practice of yoga postures or whether they occur
in a metabolically matched walking intervention. We hy-
pothesize that improvement in mood scores correlate posi-
tively with GABA levels, while anxiety scores will correlate
negatively with GABA levels.
Materials and Methods
Subjects were recruited from the community by newspa-
per ads, flyers, and the Internet. Screening interviews and
written informed consent were obtained at Boston University
School of Medicine General Clinical Research Unit. Eligible
subjects were randomized in permuted blocks (n¼4) to a 12-
week intervention of either Iyengar yoga or walking for three
60-minute sessions per week, with a maximum of 36 ses-
sions. All subjects had three MRS scans: Scan 1 at baseline;
Scan 2 after their 12-week intervention; immediately after
Scan 2, all subjects completed a 60-minute yoga or walking
intervention, depending on group assignment, which was
immediately followed by Scan 3.
Participants were 18–45 years old with no current Axis I
diagnosis. Nonpsychoactive medications were allowed if the
subject had been on a stable dose for at least 1 month with no
anticipated changes during the study. The following items
were exclusionary: any yoga practice in the previous 3
months, or a lifetime history of one yoga session/week for
?4 weeks; current participation in psychotherapy, prayer
groups, or any mind–body disciplines; a neurological dis-
order or medical condition that would compromise subject
safety or scan data; treatment within the previous 3 months
with medications that might affect the GABA system; use of
tobacco products (known to affect GABA levels)12; alcohol
consumption >4 drinks/day; and contraindication to mag-
netic resonance evaluation.
The following instruments were used for screening: the
Structured Clinical Interview for Diagnostic and Statistical
Manual of Mental Disorders IV to identify Axis I Disorders13
and the Time Line Follow Back to assess alcohol consump-
tion.14,15Two (2) reliable and valid psychologic scales were
selected to monitor the effects of the interventions on mood
and anxiety over time. Mood was assessed with the Exercise-
Induced Feeling Inventory (EIFI), which has four subscales:
Positive Engagement, Revitalization, Tranquility, and Phy-
sical Exhaustion.16Anxiety was assessed with the State scale
of the Spielberger State–Trait Anxiety Inventory (STAI).17
The EIFI and STAI-State were given before each scan, prior
to the first intervention session (week 0), and after comple-
tion of sessions at weeks 4, 8, and 12.
Metabolic equivalents (METs) are used to rate and com-
pare the physical demands of various activities.18The
American College of Sports Medicine list of metabolic
equivalents was consulted to match the 60-minute Iyengar
yoga intervention with a 60-minute walking intervention at
2.5 miles per hour (mph) on a flat surface rated at 3.0METs.
During the intervention, the Physical Activity Recall (PAR), a
valid and widely used instrument, was used to convert each
subject’s weekly physical activity outside of the intervention
into a METs score.19,20For each group, the mean weekly PAR
METs scores was computed.
Certified Iyengar yoga instructors taught the yoga inter-
ventions, which were monitored by the Principal Investigator
to ensure consistency in presentation of weekly posture se-
quences. Written lists of the weekly sequences and pictures of
the postures were given to the subjects.21After 4 weeks of
instruction, subjectswereencouragedtopracticeathome.The
intrascanyogasequencewastaughtinclassandmonitoredby
research staff during Imaging Session II. The structure of the
walking intervention was designed to be similar to that of the
yoga intervention, with weekly group sessions in which
subjects walked around the gym perimeter at 2.5mph for
60 minutes. The intrascan walking session was done on a
treadmill set to 2.5mph with 0 incline. This design controlled
for group effects and interaction time with research staff.
Imaging
Subjects were scanned on a 4-Tesla full-body MR scanner
(Varian/UnityInova, Varian Inc., Palo Alto, CA) at Mclean
Hospital in Belmont, MA. Scout images confirmed optimal
positioning. After global shimming on unsuppressed water,
T1-weighted anatomical images were taken in sagittal and
axial planes [echo time (TE)/repetition time (TR)¼6.2 sec-
onds/11.4 milliseconds, field-of-view¼22?22?8cm (sagittal)
and 22?22?16cm (axial), readout duration¼4ms, receive
bandwidth¼?32kHz, in-plane matrix size¼ 128?256?16
(sagittal) and 256?256?64 (axial), in-plane resolution¼
0.94?1.9mm (sagittal) and 0.94?0.94mm (axial), readout
points¼512, slice-thickness¼2.5mm, flip-angle¼118].
In our previous study, a post-hoc regional analysis that
used multivoxel spectroscopic imaging showed that the
greatest increase in GABA levels after the yoga intervention
was in the thalamus.8The selection of the left thalamus was
based on evidence that the left side has greater parasympa-
thetic innervations and that GABA levels are lower in the left
thalamus in post-traumatic stress disorder subjects.22,23For
this study, an algorithm was developed to position a 2?2?3-
cm voxel over the left thalamus. Proton spectroscopy
implemented a MEGAPRESS [MEscher-GArwood Point-
Resolved Echo Spectroscopy Sequence] difference-editing
sequence specifically tuned for GABA.24Manual voxel
shimming yielded global water-line widths ranging from 8 to
15Hz. The MEGAPRESS sequence collected 68-millisecond
echo-time spectra in an interleaved fashion where the GABA
editing pulse was applied on every second transient. Addi-
tional MEGAPRESS acquisition parameters were: TR¼2 sec-
onds,spectral-bandwidth¼2kHz,
milliseconds, Number of Excitations (NEX)¼384, and total
scan duration¼13 minutes.
readout-duration¼512
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FIG. 1.
Flow chart of subject recruitment through completion. GABA, g-aminobutyric acid.
3

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In order to quantify GABA, the difference-edited spectra
were processed and then fitted with LCModel using basis sets
acquired at 4T. A separate LCModel template was used to fit
the unedited 68-milisecond subspectrum to obtain creatine
(Cr). All fitted metabolite areas were normalized to the fitted
Cr resonance from the 68-millisecond subspectrum. One (1)
spectrum from the MEGAPRESS acquisition in the thalamus
was excluded from analysis due to low signal-to-noise.
GABA/Cr ratios are referred to as GABA levels. In order to
ascertain the gray and white matter contribution to each
voxel,theaxialT1-weightedimagesweresegmentedintogray
matter, white matter, and cerebrospinal fluid compartments
using the commercial software package FSL 4.1 (FMRIB
Software Library; Analysis Group, FMRIB; Oxford, UK).
Statistical analysis
The primary outcome variables were mood scores, anxiety
scores, and thalamic GABA levels. Continuous measures
were summarized by means?standard deviations; within-
group comparisons were performed using paired t-tests,
while between-group comparisons were performed using
two-sample t-tests. Discrete measures were summarized by
raw counts for numerators and denominators, as well as the
associated percentages, and were compared by Fisher’s exact
test due to the limited sample size. Linear regression analysis
was used to quantify the association between the primary
outcome variables and potential predictor variables. In order
to take into account within-subject correlations arising from
repeated longitudinal measurements, generalized estimated
equations (GEEs) were used to analyze within-group trends
in mood and anxiety scores, as well as to perform between-
group analyses.25,26All hypothesis tests were two-tailed and
conducted at the a¼0.05 significance level. Confidence in-
tervals were two-sided and were constructed with 95% con-
fidence. Stata 10.0 (College Station, TX) was used for analysis.
Results
Demographics and study participation
Thirty-four (34) subjects completed the study: 19 in the
yoga group and 15 in the walking group (Fig. 1). There was
no significant difference between groups for demographic or
descriptive variables except for height, which although sta-
tistically significant due to a relatively small standard devi-
ation was clinically not significant. There was no difference
in demographics between study completers and dropouts,
Table 1. Demographics and Study Participation
Yoga group
(n¼19)
Mean?SD
23.9?3.0
11 (58%)
18 (95%)
16.4?1.1
91.6?6.9
14.8?15.5
0.4?0.6
0.0?0.0
23.8?22.4
0.3?0.2
1.7?0.1
68.2?12.5
22.5?2.9
11.3?10.6
8.5?16.1
23.4?7.5
0.9?1.0
Walking group
(n¼15)
Mean?SD
25.6?4.9
11 (73%)
12 (80%)
16.7?1.4
89.3?15.8
8.7?7.4
0.4?0.7
0.0?0.0
13.9?11.3
0.2?0.1
1.7?0.1
65.6?10.9
23.8?2.7
24.8?22.90
19.5?24.9
24.8?6.2
Factort dfp
Age
Female
Single
Years of education
Possible drinking days
Actual drinking days
Heavy drinking days
Very heavy drinking days
Total drinks
Average drinks/possible drinking days
Height (m)
Weight (kg)
Body–mass index
PARs (during 12-week intervention)
PARs week prior to scan 2
Attendance (of 36)
Home yoga sessions/week
?1.25
–
–
?0.74
0.56
1.41
0.09
–
1.57
1.41
2.43
0.64
?1.33
2.35
1.57
0.59
?
32
–
–
32
32
32
32
32
32
32
32
32
32
32
32
32
?
0.22
0.48
0.30
0.46
0.58
0.17
0.93
–
0.13
0.17
0.02
0.53
0.19
0.02
0.13
0.56
?
SD, standard deviation; df, degrees of freedom; PAR, Physical Activity Recall.
Table 2. Generalized Estimated Equations Analysis of Mood and Anxiety Scales During Interventions
Yoga group Walking group Difference
betazp betazpbetazp
EIFI-Positive Engagement
EIFI-Revitalization
EIFI-Tranquility
EIFI-Physical Exhaustion
STAI-State
0.792
3.069
1.923
?1.343
?4.517
2.50
4.46
3.10
?1.86
?2.11
0.01
<0.001
0.002
0.06
0.04
?0.450
1.771
?0.226
0.931
2.415
?0.93
2.01
?0.28
0.99
1.05
0.35
0.04
0.78
0.32
0.30
1.424
2.359
2.394
?2.275
?6.088
2.58
2.15
2.42
?1.95
?1.93
0.01
0.03
0.02
0.05
0.05
EIFI, Exercise-Induced Feeling Inventory; STAI, State–Trait Anxiety Inventory.
4 STREETER ET AL.

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Table 3. Tonic and Acute Changes in Thalamic Gamma-Aminobutyric Acid Levels
TonicScan 1Scan 2(Scan 2–Scan 1)tdfp
Yoga group
Walking group
0.065?0.020
0.059?0.023
Scan 2
0.061?0.021
0.060?0.014
Scan 3
?0.004?0.017
0.000?0.020
(Scan 3–Scan 2)
?1.01
0.04
18
14
0.33
0.97
Acutetdfp
Yoga group
Walking group
0.058?0.018
0.060?0.014
0.067?0.019
0.059?0.019
0.009?0.020
?0.000?0.017
1.80
?0.10
17
14
0.09
0.92
df, degrees of freedom.
FIG. 2.
ing an increase in the area of
the edited g-aminobutyric acid
(GABA) resonance doublet at
3.00 parts per million (ppm)
from scan 2 to scan 3 for the
left thalamic voxel in the yoga
group. Glx, glutamate and
glutamine complex; MRS,
magnetic resonance spectros-
copy; NAA, N-acetylaspartate;
MM, macromolecules.
Spectral data show-
Table 4. Significant Correlations of Thalamic Gamma-Aminobutyric Acid Levels with Mood and Anxiety Scores
Scan(s)rhot dfp
Correlation of thalamic GABA levels with mood and anxiety scores
Whole group
Revitalization
Tranquility
Tranquility
STAI-S
STAI-S
Correlation of changes in thalamic GABA levels with changes in mood and anxiety scores
Yoga group
Revitalization2-1
Tranquility 2-1
STAI-S 2-1
Tranquility3-2
1
1
2
2
3
0.38
0.50
0.47
?0.35
?0.41
2.32
3.27
3.01
2.11
2.46
32
32
32
32
30
0.03
0.003
0.005
0.04
0.01
0.78
0.50
?0.50
0.56
5.14
2.38
2.38
2.70
17
17
17
16
0.001
0.03
0.03
0.01
GABA, g-aminobutyric acid; df, degrees of freedom; STAI, State–Trait Anxiety, Inventory.
5

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withdropoutsequallydividedbetweeninterventions(Table1).
The means for the weekly PAR METs during the 12-week
intervention showed the walking group to have a signifi-
cantly greater level of activity outside the intervention than
the yoga group (p¼0.02); however, there was no difference
between groups in activity levels on the week before Imaging
Session II. Out of 36 sessions, each group attended about two
thirds, with the yoga group reporting about one session a
week at home.
Analysis of mood and anxiety scales and GABA levels
The following analyses were done with statistically sig-
nificant findings reported in the tables: (1) a GEE model for
changes in mood and anxiety scores for each group at weeks
0, 4, 8, and 12; (2) tonic changes in GABA levels were as-
sessed over the course of the intervention by subtracting
Scan 1 from Scan 2 values, while acute changes associated
with the intrascan session were assessed by subtracting Scan
2 from Scan 3 values; (3) tonic and acute changes in GABA
levels; (4) correlations of mood and anxiety scores with
GABA levels for each scan; (5) correlations of tonic (Scan 2–1)
and acute (Scan 3–2) changes in mood and anxiety scores
with tonic and acute changes in GABA levels.
In the three ‘‘positive’’ subscales of EIFI (Positive En-
gagement, Revitalization, and Tranquility), an increase in
score indicates improved mood. In the two ‘‘negative’’ scales,
the STAI-State and EIFI-Physical Exhaustion, an increase in
score indicates increased anxiety and physical exhaustion,
respectively. Inverse associations (-beta), with the negative
scales, indicate decreased anxiety in the within-group anal-
ysis and greater decrease in anxiety for the yoga group in the
between-group analysis.
In the GEE analysis, the yoga group showed increased
scores over the course of the intervention in the three positive
EIFI subscales (Positive Engagement, Revitalization, and
Tranquility), while the walking group showed an increase in
the EIFI-Revitalization subscale. The yoga group showed a
decrease in the STAI-State score, indicating decreased anxi-
ety. The between-group analysis showed the yoga group to
have greater increases in all positive scales and greater de-
creases in all negative scales compared with the walking
group, indicating improved mood, decreased anxiety and
decreased exhaustion (Table 2).
Tonic changes in mean mood scores showed significant
increases in the yoga group for Revitalization (1.8?2.5,
t¼3.21, df¼18, p¼0.005). Acute changes in mean scores
indicated significant increases in the yoga group for Re-
vitalization (2.5?2.7, t¼4.12, df¼18, p<0.001) and Tran-
quility (2.0?1.8, t¼4.77, df¼18, p<0.001), and significant
decrease in the STAI-State (?5.2?5.5, t¼?4.05, df¼17,
p<0.001). There were no significant tonic or acute changes
detected in the walking group.
Analysis of the gray matter/white matter ratio in the
thalamic voxel was done for each of the three scans. There
was no difference in the average gray matter/white matter
ratio among the three scans for the thalamus (F¼0.11, df¼2,
p¼0.90), indicating consistent repositioning of the voxel
over the same anatomical region for each scan. There was no
difference between the yoga and walking group in baseline
GABA levels (t¼0.73, df¼32, p¼0.47). There were no sig-
nificant changes in tonic GABA levels in either group. There
was a nearly significant increase in acute thalamic GABA
levels in the yoga group (0.009?0.019, t¼1.80, df¼17,
p¼0.09) (Fig. 2 and Table 3).
Whether thalamic GABA levels correlate with improved
mood or decreased anxiety is a general question, indepen-
dent of group assignment. Therefore, the correlation of mood
and anxiety scores with GABA levels was done for the whole
group. There were significant positive correlations of GABA
levels with Revitalization and Tranquility scores and a neg-
ative correlation with the STAI-State scores (Table 4).
In the yoga group, for the tonic condition, there were
positive correlations of changes in mood and anxiety scores
with changes in mean GABA levels for Revitalization and
Tranquility scores and a negative correlation with the STAI-
State, while in the acute condition there were positive cor-
relations with Tranquility scores (Table 4).
Women (n¼22) used an approved method of birth control
and had negative urine pregnancy tests prior to each imag-
ing session. Because decreases in GABA levels occur during
the follicular phase, women were scheduled for scanning in
the nonluteal stage defined by a serum progesterone
<3.0ng/mL.27All women, except 1 using hormonal con-
traception and assumed to be in the nonluteal stage, had
progesterone levels drawn before each imaging session.
Serum progesterone levels were <2.0ng/mL for all but four
samples. Two (2) women had levels <5.2ng/mL for imaging
session I. For imaging session II, serum progesterone levels
were 20.2ng/mL for 1 subject in the walking group, and
17.3ng/mL for one subject in the yoga group, consistent
with the luteal phase that is associated with higher GABA
levels. Increases in GABA levels due to the luteal phase
during imaging session II would have made tonic increases
easier to detect, yet there was no significant increase in tonic
GABA levels for either group. In the previous study, in the
yoga group, menstrual stage did not affect increases in
GABA levels. Accordingly, the luteal levels of progesterone
for imaging session II should not have affected the detection
of acute changes.
Discussion
In this study, the yoga intervention was associated with
greater improvements in mood and decreases in anxiety in
the tonic, acute and intervention analyses compared to the
metabolically matched walking intervention, suggesting that
the effect of yoga on mood and anxiety is not solely due to
the metabolic demands of the activity. In our prior study,
significant acute increases in brain GABA levels immediately
after a yoga session were recorded. The current study found
near-significant acute increases, but stable tonic levels during
the 12-week yoga intervention. These observations are con-
sistent with a time-limited effect of the yoga intervention on
thalamic GABA levels. The lack of tonic changes in this
study, and the lack of baseline differences between the ex-
perienced yoga practitioners and controls in the prior study,
suggest that tonic GABA levels are stable in subjects
screened to exclude low GABA states.
The whole group analysis of the correlations between
mood and anxiety scales taken before each scan and the
GABA levels obtained from those scans demonstrated sig-
nificant positive correlations with the positive scales of
Tranquility and Revitalization and a negative correlation
6 STREETER ET AL.

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with the STAI-State. To our knowledge, this is the first study
to report a positive correlation between thalamic GABA levels
and improved mood or decreased anxiety. The correlations
between group changes in mood and anxiety scores and
changes in GABA levels in the tonic and acute conditions
suggest that increases in thalamic GABA levels are associated
with improved mood and decreased anxiety. This is the first
study to show that a behavioral intervention (i.e., yoga) is as-
sociated with a positive correlation between changes in tha-
lamic GABA levels and improvements in mood and anxiety.
The use of METs controlled for metabolic demands of each
intervention and allowed the activity level of the 2 groups
(outside of the intervention) to be compared. The signifi-
cantly greater level of physical activity outside the inter-
vention in the walking group compared to the yoga group
was not expected. The higher level of outside activity in the
walking group could have contributed to the finding of
smaller changes in mood and anxiety in the walking group,
as the intervention may not have been a great enough
physical challenge given the greater level of outside activity.
The small sample size in the yoga group where only a
nearly significant increase in thalamic GABA levels was de-
tected was a limitation, which was offset by the findings of
significant correlations between GABA levels and mood and
anxiety scores. In our previous study, the acute increase in
whole-slab GABA levels in experienced yoga practitioners
was 27% (published) and a 26% increase in thalamic GABA
levels (unpublished), compared to a 13% thalamic increase
seen in the current study of yoga-naı ¨ve subjects who were
trained for 12 weeks.8This suggests that while subjects can
be trained to practice yoga in a relatively short time with a
measurable effect, the associated change in GABA levels may
increase with experience.
The effect of the yoga intervention on GABA levels may
be due to the ability of yoga practices to increase para-
sympathetic nervous system (PNS) activity.28–30In a study
comparing Iyengar yoga to a walking control, the Iyengar
yoga group showed greater increases in PNS activity.31
Yoga techniques and vagal nerve stimulation (VNS) in-
crease PNS tone by stimulating vagal afferents.1,32Studies
suggest that the antiepileptic effects of VNS are largely
mediated by widespread release of GABA.33Accordingly,
the practice of yoga through stimulation of vagal afferents
may result in the increase of brain GABA levels as seen
in the yoga group.
Conclusions
The 12-week yoga intervention was associated with
greater improvements in mood and anxiety than a meta-
bolically matched walking exercise. This is the first study to
demonstrate that increased thalamic GABA levels are asso-
ciated improved mood and decreased anxiety. It is also the
first time that yoga postures have been associated with a
positive correlation between acute increases in thalamic
GABA levels and improvements in mean scores on mood
and anxiety scales. Given that pharmacologic agents that
increase the activity of the GABA system are prescribed to
improve mood and decrease anxiety, the reported correla-
tions are in the expected direction.34,35The possible role of
GABA in mediating the beneficial effects of yoga on mood
and anxiety warrants further study.
Acknowledgments
We acknowledge the certified Iyengar yoga teachers with-
out whom this project would not have been possible: Marysia
Gensler, Annie Hoffman, Nancy Turnquist, and Lynnae Le-
Blanc. Funding for this study was provided through NIH
grants: 1R21AT004015 (CCS), DAO15116 (PFR), R01 1AA
015923 (DAC), M01RR00533 and Ul1RR025771 (General
Clinical Research Unit at Boston University Medical Center).
Disclosure Statement
Dr. Renshaw is a consultant for Novartis, Roche and Kyowa
Hakko and received research support from GlaxoSmithKline
and Roche. Dr. Ciraulo is a consultant for Novo Nordisk and
received research support from Merck and Catalyst.
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Address correspondence to:
Chris C. Streeter, MD
Division of Psychiatry
Boston University School of Medicine
85 East Newton Street, M912-E
Boston, MA 02118
E-mail: streeter@bu.edu
8 STREETER ET AL.