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Preliminary findings support the potential of yoga as a complementary
treatment of depressed patients who are taking anti-depressant medications
but who are only in partial remission. The purpose of this article is to
present further data on the intervention, focusing on individual differences
in psychological, emotional and biological processes affecting treatment
outcome. Twenty-seven women and 10 men were enrolled in the study, of whom
17 completed the intervention and pre- and post-intervention assessment
data. The intervention consisted of 20 classes led by senior Iyengar yoga
teachers, in three courses of 20 yoga classes each. All participants were
diagnosed with unipolar major depression in partial remission.

Psychological and biological characteristics were assessed pre- and post-intervention,
and participants rated their mood states before and after each class.
Significant reductions were shown for depression, anger, anxiety,
neurotic symptoms and low frequency heart rate variability in the 17 completers.
Eleven out of these completers achieved remission levels post-intervention.
Participants who remitted differed from the non-remitters at intake on
several traits and on physiological measures indicative of a greater
capacity for emotional regulation. Moods improved from before to after the
yoga classes. Yoga appears to be a promising intervention for depression; it
is cost-effective and easy to implement. It produces many beneficial
emotional, psychological and biological effects, as supported by
observations in this study. The physiological methods are especially useful
as they provide objective markers of the processes and effectiveness of
treatment. These observations may help guide further clinical application of
yoga in depression and other mental health disorders, and future research on
the processes and mechanisms.


Yoga as a Complementary and Alternative Treatment of Depression

Approximately 75% of US adults have used some form of complementary or
alternative medicine (CAM), and about 5% report depression or anxiety as a
motivating factor.[1] CAM practices for depression include yoga,
acupuncture, massage, St John's Wort (hypericum), S-adenosylmethionine
(SAMe) and folate.[2] In an unpublished survey of 2133 yoga students
conducted by the Iyengar Yoga National Association of the US (IYNAUS),
depression ranked among the top five reasons given for participation.

Yoga continues to grow in popularity.[3] A survey conducted in 1998[4] estimated
that 15 million American adults used yoga at least once in their lifetime
and 7.4 million during the previous year, and concluded that yoga was often
regarded as helpful and without expenditure. Despite the popularity of yoga,
there is little systematic research on its clinical application to mental or
other health conditions and on the processes underlying its therapeutic
potential. Khumar et al.[5] investigated yoga for depressed university
students and found it superior to a no-treatment control; this form of yoga
emphasizes deep relaxation and rhythmic breathing. Janakiramaiah et al.[6]
randomized participants to electroconvulsive therapy, imipramine or a
Sudarshan Kriya yoga programme focused on rhythmic breathing. They reported
remission rates of 93% for electroconvulsive therapy (ECT), 73% for
imipramine and 67% for yoga. Studies of non-clinically depressed adults have
unclear implications for patients with mood disorders.[7-9] These studies
were not placebo-controlled, which is a limitation given the magnitude of
placebo effects in the treatment of depression.[10] Yoga as a complement to
anti-depressant medication has not been studied.

Iyengar Yoga

An important role in making yoga accessible to the West was played by B. K.
S. Iyengar (1918-). The approach he articulated[11,12] makes it well suited
to biomedical application. First, Iyengar yoga employs 'props' (e.g. mats,
blankets, blocks, ropes, chairs) that allow beginners to learn the poses
gradually and accurately, despite limited experience and flexibility.
Second, Iyengar yoga teachers undergo a 3-year training program and are
certified by the organization (IYNAUS) at different ranks (Introductory,
Intermediate and Senior, with levels within each) according to years of
teaching experience and competence. Qualifications are evaluated by written
and teaching performance tests, judged by panels of senior teachers. This
standardization supports the reproducibility of the program, somewhat like
the 'manualized' psychotherapies. Third, Iyengar theory and practice
specifies asanas (poses, postures, positions) and sequences of asanas that
have therapeutic value for different conditions and states, including
depression. For example, certain asanas have been found to enhance positive
mood in healthy (non-depressed) participants.

Iyengar yoga classes typically involve the practice of floor, sitting and
standing poses, inversions (head stand, shoulder stand), breathing exercises
(pranayama) and short periods of relaxation at the end of each class
(savasana--corpse pose). Stretches, twists and extensions or expansions of
parts of the body such as the chest are common features. The instructions
given by teachers are detailed and continuous during classes, with a focus
on awareness of the activity of muscles and joints in conjunction with
appropriate breathing patterns to achieve the ideal performance of each
asana. An important feature of participation in Iyengar yoga is sustained
attention and concentration.

Research Objectives

The purpose of this article is to present further data obtained in a study
of yoga as a complementary treatment of depressed patients who were taking
anti-depressants, but who still had residual symptoms of depression[13] and
to provide evidence underlying the potential of yoga as a treatment of
depression.[14] In the initial sample of 25 adults with major depression,
yoga augmentation resulted in significant improvements in mood, and
depression severity scores decreased significantly from pre-to
post-treatment for these subjects who were taking anti-depressant
medications and yet had residual symptoms. An additional group of 12
participants who underwent the same intervention were added to the study
sample for the current report.

Psychological and Biological Factors Affecting Treatment Outcome

The focus is on individual characteristics and aspects of the process that
affect response to the yoga intervention. We consider various psychological
and biological variables related to depression and mood disorders and to
presumed effects of psychological and activity-based treatments, including
direct measures of depression, demographics, personality tests designed to
tap emotional dispositions and symptoms related to depression (such as anger
and anxiety), scales of physical and emotional fitness, and measures of
autonomic nervous system (ANS) functions.

The ANS measures included blood pressure (BP) and heart rate (HR), and
derived indices of heart rate variability (HRV) and baroreflex sensitivity
(BRS). High-frequency HRV (HF-HRV) is a measure of respiratory sinus
arrhythmia, indicative of parasympathetic control of the heart (vagal tone).
The evidence in various studies supports the polyvagal theory of Porges on
the role that vagal tone plays in social behavior and the regulation of
emotions.[15] The baroreflex also contributes to parasympathetic control of
the heart, and low BRS may be a marker of increased cardiac risk associated
with depression or comorbid anxiety.[16-20] HRV and BRS are both relevant to
depression, and they are also relevant to the effects of exercise.[21-23]

Variations in HRV

Studies have found HF-HRV reflections of vagal tone to be lower in depressed
psychiatric patients compared with controls,[24-26] although some have
not.[27] There is more consistent evidence that HRV is lower in depressed
than non-depressed patients with stable coronary disease,[22,28] or with a
recent history of acute myocardial infarction.[29] In a recent study in our
laboratory,[30] we compared 28 depressed patients from the present sample
with 28 healthy controls on whom we had the same measures. Each pair of
subjects was matched for age, gender and ethnicity. The patients showed
autonomic function imbalance as indicated by higher low-frequency HRV
(LF-HRV) and ratio of low to high frequency HRV (LF/HF), reduced HF-HRV and
lower BRS. This dysfunctional pattern was associated with higher HR and BP.
HF-HRV has also been related to depressed mood during stressors.[31] As to
the effects of interventions on HRV, research findings are inconsistent.
Studies involving pharmacologic treatments for depression[23,32] and
psychotherapy[33] report an increase in HRV with successful treatments,
whereas electroconvulsive therapy[34] resulted in a decrease in HRV,
associated with successful treatment. The discrepancies may reflect the
specific intervention employed. As to BRS, in a study of healthy elderly
people comparing aerobic exercise and yoga in a 6-week training program,
yoga increased BRS but aerobic exercise did not.[35]

Yoga and Mood

As mood changes are central in depression and mood disorders more generally,
we also evaluated the role in treatment outcome of self reports of mood
changes occurring during the yoga classes. This focus derives from previous
research on the effects of yoga on mood reports in non-depressed healthy
subjects, suggesting the potential of yoga for use in the management of
clinical major depression. In a form of yoga (Hatha Yoga) that has a strong
exercise dimension much like Iyengar yoga, with stretching, balancing and
breathing routines, subjects reported being less anxious, tense, angry,
fatigued and confused after classes than just before class and, in a second
study, yoga and swimming showed comparable positive effects on mood
reports.[36,37] More recently, in a non-clinical sample, reductions in
negative mood occurring from before to after yoga classes were greater for
subjects scoring higher on scales of depression and anxiety than those
scoring lower on these traits.[8,9,38]

We are reporting on data in a single-group outcome study. Our intention was
to estimate the size of the effect, examine process variables and individual
differences in treatment outcome, as well as consider practical issues in
research of this kind in this population of patients.



This research adhered to ethical research standards and was approved by the
UCLA Institutional Review Board.

Participants were recruited by flyers on campus bulletin boards, newspaper
advertisements and internet notices, and letters to UCLA clinical faculty.
Thirty-seven people qualified for the study after telephone screening and
intake diagnostic interview, 27 women and 10 men; 33 White, 1 African, and 3
Asian-American; mean (range), age 44.8 (20-71); years of education
16.8;[12-21] BMI 26.7;[20-55] hours of exercise/week 5.4 (0-30); alcohol
drinks/week 1.3 (0-8); 6 students, 3 retirees, 2 unemployed, 26 in
professional, technical and white collar occupations.

Based on history and intake diagnostic interview (Mini-International
Neuropsychiatric Interview),[39] all participants were diagnosed with
unipolar major depression in partial remission; partial remission was
operationalized as having self-reported improvement in depression severity
with pharmacotherapy, but with residual symptoms reflected by scores on the
17-item Hamilton Depression Scale (HAM-D) of 7-18. Participants had to be
under the care of a physician and taking anti-depressant medication for at
least 3 months, which continued during the study. The average Hamilton-D17
(HAM-D) score at intake was 12.5;[7-18] number of depressive episodes
2.8;[1-6] months on medication 75.6 (3-336). Participants were excluded (i)
for Axis I diagnoses of bipolar disorders, delirium or dementia,
schizophrenia or other psychotic disorders, or current substance-related or
eating disorders; (ii) for any medical illness or other conditions that
would pose a safety concern or limit participation; (iii) for suicidal
thoughts or tendencies. Medication type was as follows: selective serotonin
reuptake inhibitor (SSRI) (n =3D 15); serotonin-norepinephrine reuptake
inhibitor (SNRI) (n =3D 4); Dopaminergic (n =3D 4); augmented/combination drug
regimen (n =3D 14). Medication category was unrelated to treatment outcome
after the yoga intervention. Individuals with > 3 months of prior yoga
experience were excluded. The protocol was approved by the UCLA
Institutional Review Board, and informed consent was obtained from all
participants. Approval for participation in the study was obtained from each
participant's own treating physician.

Attendence and Adherence

Out of the 37 people who qualified for the study and completed the intake
procedures, six did not attend any classes, six attended one class, two
attended two classes, one attended three classes and one attended five
classes. None of these 16 participated in the final assessment and few
responded to telephone inquiries. Based on some limited feedback from these
people and informal observations of research assistants, the issues were
difficult in making a commitment in general, conflicts with other
activities, various inconveniences or concern about the physical demands.
The remaining 21 attended six or more sessions, which we estimated would be
likely to have an effect. These 21 are labeled 'Ins' and the other 16
'Outs'. The 16 Outs included 12 women and 4 men; the 21 Ins included 15
women and 6 men.

Of the 21 Ins, four (19%) did not return for the final assessment or respond
to telephone calls. These four dropouts (all women) attended 10, 12, 12 and
17 sessions. The remaining 17 are labeled Completers (11 women, 6 men).
Thus, the primary participants were the 17 who attended six or more sessions
and who completed both intake and post-intervention assessments.

Eleven participants (65%) ended the study at remission levels (REMISS, < 7
on HAM-D); for the remaining six participants (Non-Remiss), one showed a
sizable reduction (14-9) and the other five small changes. The REMISS group
contained six women and five men; the NON-REMISS group contained five women
and one man.

Yoga Procedure

Yoga instruction was provided in three groups of 12-13 participants over an
8-week period, three sessions a week with a total of 20 sessions per group
because of holidays and incidental cancellations. The 60-90 min classes were
led by three highly experienced certified Iyengar yoga teachers who rotated
over the sessions. The three groups did not differ in attendance rates or in
the HAM-D or Quick Inventory of Depressive Symptoms (QIDS) scores. Yoga
instruction followed sequences of yoga asanas, specifically designed by the
teachers for this study to improve mood and alleviate depression, based on
the writing and teaching of BKS Iyengar[11,12] and other leaders in the
field.[40,41] There were three classes every week. One of the classes
focused on inverted poses such as Salamba Sarvangasana (shoulderstand) and
Viparita Karani (supported inversion with bolsters and wall). The poses were
introduced in stages in a progressive manner week by week according to the
ability of the students. The inversion sequence eventually incorporated
poses such as Adho Mukha Vrksasana (Handstand) and Sirsasana (headstand). A
second class each week focused on backbends which emphasized the expansive
chest opening aspects of back arching asanas in both supported (with chairs,
bolsters, block, etc.) and unsupported versions. The third class every week
focused on restorative poses using props in a specific manner to support the
student in backbends, inversions and supine poses in order to be able to
hold the poses longer and cultivate the relaxing benefits in the pose in
addition to the other properties in the pose that help elevate mood. As in
the aforementioned inversion sequence, the back bending and restorative
sequences were also taught in a progressive manner. The yoga teachers were
not given any information about the participants' individual characteristics
or research data. A complete list of the asanas may be obtained on request.


Psychological Measures. The intake and post-intervention assessment
consisted of a diagnostic interview and health history, demographic
questionnaire and the following personality tests: 17-item HAM-D, QIDS, SCL,
Spielberger Anger Expression Scale providing indices of Anger In
(suppression of anger, ANGIN) and Anger Out (expression of anger, ANGOUT),
Spielberger Trait Anxiety Inventory (STAI), Cook-Medley Hostility Scale
(indirect hostility), Pittsburgh Sleep Scale (SLEEP), and the SF-36
short-form health survey, which includes eight dimensions related to
physical and emotional limitations on functioning, bodily pain, general
mental health, vitality, general health, limitations in usual role
activities related to physical and to emotional problems. As significant
effects were found only for the last dimension on emotional limitations in
role activities (RESF36), for simplicity data for the other SF-36 dimensions
will not be presented. The primary outcome measure of therapeutic effect was
the change in HAM-D score from intake to post-intervention.

The electrocardiogram and continuous BP (Finapres) were measured for 20 min
in a soundproof laboratory under resting conditions with no other tasks or
stimulation. Aside from measures of HR and BP, the HR variances of residual
time series (the filtered waveforms) after a band-pass optimal FIR (finite
impulse response) filtering for alien frequencies and baseline trend were
used to calculate HR variability (HRV, ms2) in two frequency bands: low
frequency (LF-HRV, 0.075-0.125 Hz) and high frequency (HF-HRV, 0.125-0.50
Hz); LF-HRV measures both sympathetic (SNS) and parasympathetic (PNS) =
HF-HRV measures PNS influences on the heart. The specific indices were =
log-transformed variance of HF-HRV and LF-HRV, ratio of the =
variance of LF-HRV to the sum of the logs of the two bands (LFTOT-HRV),
ratio of log-transformed variance of HF-HRV to the sum of the logs of =
two bands (HFTOT-HRV) and ratio of log-transformed variance of LF-HRV to
log-transformed HF-HRV (LFHF-HRV).

A measure of BRS was obtained by the Sequence Method developed by Andrew
Steptoe.[42] BRS indicates how the ANS adapts to fast changes in BP by
measuring the slope of the change in the cardiac interbeat interval to a
successive increase or decrease in BP over a minimum of three beats. For
further details of the physiological recording and data processing methods
see reference.[30]

Mood Ratings

Participants were asked to rate their moods before and after each class from
1 =3D not at all to 5 =3D very much for each of the 20 mood items. The moods
were selected to tap three dimensions of affective state: positive (happy,
relaxed, optimistic, confident, content), negative (stressed, sad,
frustrated, irritated, depressed, anxious, blue, angry, pessimistic) and
energy-arousal (attentive, fatigued, alert, tired, energetic, sleepy).[43]

Data Analysis

Systat (v. 10) was used to analyze the data using within- and between-group
t-tests and general linear models (GLM). An example of the latter is the
analysis of the effects of an independent variable, such as whether
participants achieved remission levels or not versus the repeated measure of
change in HAM-D scores from pre- to post-intervention. Random regression
models (SAS, Proc Mixed) were used to analyze the longitudinal mood ratings
obtained over the course of the yoga sessions. These models consider both
within- and between-subject variability, and allow for random and fixed
effects (mixed modeling) as well as a variable number of observations per
subject and missing data, such as missed sessions.


Predictors of Failure to Complete Yoga Intervention

The 21 Ins and 16 Outs were compared by t-test and chi-square test on all
measures at baseline. They differed only on one measure; Ins had higher
scores on the Anger In scale (19.3 versus 15.8; P < 0.02). Scores on the
Anger In scale were negatively correlated with total Anger (r =3D -0.50, P <
0.002) and positively correlated with Trait Anxiety (r =3D 0.53, P < 0.001),
Indirect Hostility (r =3D 0.59, P < 0.001) and Months Medication (r =3D 0.45, P
< 0.01).

Significant Pre-Post Reductions were Shown for HAM-D, STAI, ANGOUT, SCL,
RESF-36 and LF-HRV

For the 17 completers, HAM-D at intake was 12.4 (7-18) and 6.2 (0-15) at
post-intervention (P < 0.001). All but two out of the 17 showed a decrease
in HAM-D scores. For all 37 participants, using the last observation carried
forward, thus no change for the 16 Outs and the four who did not complete
the post-assessment, the mean reduction in HAM-D scores was still
significant (P < 0.001). For the 17 completers, significant pre-post
reductions (P < 0.05) were shown for STAI, ANGOUT, SCL, RESF36 and LF-HRV (
Table 1 <> ).

REMISS Participants were Less Educated and Exercised More Often Than
NON-REMISS Participants, and the Two Groups also Differed on HR, BRS and HR
Variability at Intake

Eleven participants (65%) ended the study at remission levels (REMISS, < 7
on HAM-D); for the remaining six participants, one showed a sizable
reduction (14-9) and the other five small changes. With respect to intake
(pre) measures, REMISS participants differed significantly (Ps < 0.05) from
NON-REMISS participants on intake data as follows: less education, more
habitual exercise; lower HR, higher levels of HF-HRV, lower levels of
LFHF-HRV, higher levels of HFTOT-HRV, lower levels of LFTOT-HRV and higher
BRS ( Table 2 <> ).
Given the activity-oriented intervention, we examined the relationship
between the intake measure of habitual exercise and the physiological
measures for all participants. The various high-frequency HRV measures
(vagally mediated) were positively correlated with hours of exercise (rs
0.35 to 0.40), and the low-frequency HRV measures were negatively correlated
with exercise (rs -0.25 to -0.35).

REMISS Participants showed Greater Improvement in Depressed Mood, Neurotic
Symptoms and Middle Insomnia compared with NON-REMISS Participants, and the
Two Groups also Differed on Changes in HR Variability Pre- to Post-intervention

Differences between pre- and post-intervention assessment measures were
examined as a function of whether participants achieved remission or not,
using HAM-D < 7 for stratification. REMISS participants showed greater
reductions in their QIDS and SCL scores. In addition, they also showed
several physiological effects: a reduction in HF-HRV and HFTOT-HRV compared
with increases in the NON-REMISS group and a small increase in LFHF-HRV
compared with a small decrease in the NON-REMISS participants ( Table 3
<> ).

We also examined each of the 17 items in the HAM-D to specify which symptom
factors in the HAM-D were most responsive to treatment. The effects indicate
greater improvement in depressed mood (P < 0.005) and middle insomnia (P <
0.005) for REMISS compared with NON-REMISS participants.

Significant Immediate Changes Seen in Mood After Each Class

For the 17 completers, all 20 moods showed significant immediate changes
from before to after each class (all P values < 0.0001): negative moods
decreased, positive moods increased, energy/arousal moods increased (less
tired, more energetic, etc.) ( Table 4
<> ). Moods did not
change significantly over the course of the sessions with one exception:
average levels of 'happy' (pre- and post-class ratings) increased over the
course of the sessions (P < 0.03) and the increases in 'happy' from before
to after each class became greater over the course of sessions (P < 0.03).=20

The average level of mood ratings over all the classes differed between
REMISS and NON-REMISS participants as follows: REMISS rated themselves
higher on happy, relaxed, optimistic, confident, and content, and they rated
themselves lower on frustrated, pessimistic, depressed, anxious and blue (Ps
< 0.025). The differences between REMISS and NON-REMISS participants for
energy/arousal related moods were not significant.

Comparing the REMISS and NON-REMISS groups, in five moods, the change in
rating from beginning to the end of class differed significantly. For three
negative moods (frustrated, pessimistic, anxious), the decrease was greater
for the NON-REMISS group, reflecting higher initial values for this group
(Ps < 0.05). In fact, at the end of class, the REMISS participants remained
lower. For two energy-related moods (tired, energetic), the same pattern was
shown, less tired and more energetic for NON-REMISS participants (Ps <
0.05). In these cases, the two groups had similar levels at the end of


Our findings extend prior work examining the therapeutic effects of yoga on
emotional state. First, we found that beneficial effects not only address
the biomedically defined symptoms of unipolar major depression, but yield
improvements in a more broadly defined set of reports of mood state
experience. Second, these effects are present at a session-by-session level
as well as accruing over time. Third, pre-intervention autonomic differences
were found between subjects who entered symptomatic remission with the yoga
augmentation and those who did not, suggesting that it may be possible to
consider prospectively which individuals with depression may benefit most
from complementary yoga augmentation of anti-depressant medication.

The findings of the benefits of yoga for depressed patients in partial
remission are consistent with previous studies of depressed patients[5,6]
using interventions that emphasize rhythmic breathing aspects of yoga. The
Iyengar approach in the present study focused mainly on more active asanas
and included only brief periods of relaxation and breathing exercises.
Future studies will be needed to explore the relative importance of the
various components of yoga practices (e.g. physical activity, attentional
focus, specific postures) and the mechanisms by which they produce clinical
benefits.[44] Iyengar yoga practice places a great deal of emphasis on
'opening the chest' as in the case of certain poses such as backbends, which
may have direct effects on the circulation that may elevate mood and
psychological well-being.[8]

A limitation of this study is the single-group outcome design with no
placebo or other controls. As with many unblinded interventional studies, it
is possible that the observed benefits in the present study may be related
to other factors unrelated to our intervention, such as participation in a
therapeutic program and expectations of benefit; of note, we found that the
participants' expectations assessed at intake were not correlated with
symptomatic outcome. Regular participation in a social group is another such
non-specific factor. No limitations were placed on socializing either
immediately before or after each session or at other times. Future studies
may incorporate explicit controls for this factor and should gather data on
how much socializing took place and how it affects outcome. It is noteworthy
that studies employing Iyengar yoga interventions for other conditions
(cancer survivors, self-reported emotional distress) found beneficial
effects for depression and mood as well as anxiety and physical
well-being.[45-47] These studies included control conditions.

Our remission rate of 65% compares favorably with other CAM intervention
studies: 43% using SAMe as an augmenter to anti-depressants;[48] 20% using
omega-3 fatty acid;[49] 19% using folinic acid.[50] Coppen and Bailey[51]
added folic acid or placebo to fluoxetine, and found that 65% (folate)
versus 48% (placebo) met 'recovery' criteria using a more liberal standard
for remission (HAM ? 9) than in the present study. Using their criterion,
the remission rate in our study is 77%. In a study of the effects of aerobic
exercise as a monotherapy for depression, Dunn and colleagues[52] found a
25% remission rate.

The attrition rate of 19% is lower than that occurs in exercise programs.
Pollock[53] reported that 50% of non-depressed individuals drop out of
exercise programs within 6 months. In the report by Dunn et al.,[52] 62% of
the control condition using flexibility exercises dropped out. Only one of
the many demographic, psychological and biological intake measures in the
present study discriminated those who attended six or more classes from
those who did not. Most of the latter stopped attending after one or two
sessions; 6 out of the 37 who enrolled in the study attended no sessions at
all. Reasons given for non-attendance were difficulties with transportation,
location of the venue, parking and traffic congestion, even though all who
were enrolled agreed to participate after they were informed in detail about
the arrangements.

For all who completed the study, aside from clinical symptoms of depression,
reductions were also observed in measures of anxiety, expression of anger,
neurotic symptoms, limitations on usual role activities because of emotional
difficulties, and LF-HRV. Thus, participation in yoga did not in effect
target depression only but also affected psychological and biological
processes indicative of improved mental health in general and more effective
social behavior. LF-HRV reflects both sympathetic and parasympathetic
innervation of the heart and is an indication of inadequate cardiac
parasympathetic modulation.[54] The reduction in LF-HRV, however, was not
coupled with an increase in HF-HRV, suggesting inadequate cardiac
parasympathetic modulation. From these findings, we may speculate that yoga
practice was beneficial in reducing stress responsivity, an effect which is
generally associated with sympathetic nervous system activation. The pattern
of HRV findings for those who achieved remission versus those who did not
may seem counterintuitive in that it decreased in the former and increased
in the latter. Those who achieved remission had higher levels of HRV at
intake, and the observed opposite effect may reflect the phenomenon of
regression to the mean.

We may speculate further on the reduction in HF-HRV observed in the patients
who remitted. The capacity to suppress vagal influence appears to mediate
attentional and emotional processes that allow an organism to optimally
engage or cope with environment challenges.[15,55] Resting vagal influence
and the capacity to suppress this influence have been found to be strongly
related, but the precise distinction between these mechanisms and their
concomitant behavioral processes is not yet clearly understood. This
suggests the possibility that after yoga treatment, some patients with
higher intake resting vagal tone became actively engaged in coping with
their depression and improving their mental health. For the patients with
initial lower resting vagal tone (non-remitters), yoga treatment may not
increase vagal tone to a level needed sufficient to improve their condition.
In these patients, it is possible that a longer period of treatment would be
beneficial, and future experiments may explore this possibility.

We cannot exclude the possibility that a subject's breathing pattern may be
affected by the specific yoga practices in this intervention and that such
effects may be related to the HRV findings. Both rate and depth of
respiration affect HRV[56] and may have a general effect on the autonomic
nervous system or an effect related to voluntary exercise efforts and that
may be independent of vagal control of the heart. The latter may determine
phasic respiration- but not tonic vagus-related changes in HF-HRV. One might
see reductions in respiration rate associated with the focus on breathing in
yoga practice, which would likely show up in increased HF-HRV, which was not
the case for remitters. Further investigation is warranted on the effects of
respiration and of other physiological pathways of yoga on mood and clinical

The participants who remitted differed at intake in several ways from those
who did not. They had less formal education, spent many more hours a week in
regular exercise, and had higher levels of HF-HRV, lower levels of LF-HRV
and higher BRS. The significance of the exercise and physiological effects
is understandable and suggests that remitters were already disposed to an
activity-based treatment and that from the standpoint of autonomic nervous
system functioning they had a greater capacity for emotional regulation.
Habitual exercise and physical activity appear to be beneficial for mood,
depression and mental health in general and may facilitate remission in the
treatment of depression.[57,58] The finding of less education for remitters
may be in line with a greater disposition toward an activity-based rather
than an educational or verbal therapy. In future studies, it may be
advantageous to combine meditation or other mental approaches with the
methods used in this study.

For further understanding of the differences between remitters and
non-remitters, see Fig. 1 which plots the means for six of the eight effects
in Table 2 <> and
compares them with the means of the same measures obtained in 28 depressed
and 28 matched healthy controls (30, discussed earlier). For these six
measures, the calculations were exactly the same and directly comparable. It
can be seen that for Education (Panel F) the NON-REMISS group had higher
levels and the REMISS group lower levels compared with the 'norms' for
depressed and healthy people. For exercise (Panel E), the NON-REMISS group
stands out with many fewer hours of regular exercise. As to the measures of
autonomic regulation (Panels A-D), it is apparent that the NON-REMISS
participants differed most from the healthy group in all respects with lower
BRS, higher LF/HF, lower HF-HRV and higher HR. It appears that exercise and
education may have only additive or secondary influences on the differences
between REMISS and NON-REMISS participants in baseline autonomic activity.
In general, these comparisons support the conclusion that the non-remitters
had reduced capacity for emotional regulation.


Figure 1. =20

Differences between REMISS and NON-REMISS Participants compared with data on
28 depressed and 28 matched healthy individuals (means).

The mood data indicate that remitters tended to be in a better mood
throughout the study, more positive and less negative. All participants felt
better from before to after each yoga class: more positive, less negative,
and more energetic; in fact, the non-remitters showed a greater improvement
than the remitters as their initial and overall moods were less positive to
begin with. Thus, mood improvements associated with yoga practice appear to
be universal. How they affect depression in any one person must depend on
other individual characteristics.

In conclusion, yoga appears to be a promising intervention for depression.
It is cost-effective and easy to implement. Most importantly, yoga produces
many beneficial emotional, psychological, behavioral and biological effects,
as supported by observations in this study. The physiological methods are
especially useful as they provide objective markers of the processes and
effectiveness of the intervention. The methods and observations in this
report may help guide further clinical research on the application of yoga
in depression, with appropriate placebo control and comparison conditions,
and in other mental health disorders, and in future research on the
processes and mechanisms involved.

Table 1. Pre-post yoga intervention changes (completers, n =3D 17); means

Variable Pre Post P=09
HAM-D 12.4 6.2 0.001=09
QIDS 11.9 9.4 NS=09
SCL 1.0 0.7 0.04=09
STAI 53.0 47.4 0.005=09
ANGERIN 19.9 18.1 NS=09
ANGEROUT 15.2 12.5 0.05=09
MC 15.5 16.0 NS=09
RESF36 23.1 51.3 0.02=09
SLEEP 10.2 9.1 NS=09
HR (bpm) 72.2 71.8 NS=09
SBP (mmHg) 134.0 132.5 NS=09
LF-HRV 6.81 6.51 0.05=09
HF-HRV 5.53 5.40 NS=09
LFHF-HRV 1.23 1.22 NS=09
LFTOT-HRV 0.36 0.36 NS=09
HFTOT-HRV 0.30 0.30 NS=09
BRS (ms/mmHg) 6.32 6.39 NS=09

Table 2. Significant differences between REMISS (n =3D 11) and =
6) participants at intake (means)

Education (years) 15.9 18.2 0.01=09
Exercise (h/week) 9.9 0.8 0.02=09
Heart rate (bpm) 68.7 78.4 0.04=09
HF-HRV 6.01 4.90 0.02=09
HFTOT-HRV 0.31 0.27 0.01=09
LFTOT-HRV 0.35 0.38 0.03=09
LFHF-HRV 1.14 1.38 0.01=09
BRS (ms/mmHg) 7.88 4.58 0.02=09

Table 3. Significant differences between REMISS (n =3D 11) and =
6) participants pre- and post-yoga (means)

Pre Post Pre Post=09
HAM-D 11.8 3.3 13.3 11.7 0.001=09
QIDS 13.8 6.9 9.5 12.7 0.01=09
SCL 1.1 0.7 0.8 0.8 0.04=09
HF-HRV 5.96 5.53 4.89 5.20 0.01=09
LFHF-HRV 1.16 1.19 1.38 1.26 0.02=09
HFTOT-HRV 0.32 0.30 0.28 0.29 0.002=09

Table 4. Mood ratings pre- and post-yoga classes

Mood Pre Post=09
Happy 2.9 3.5=09
Relaxed 2.6 3.8=09
Optimistic 2.8 3.3=09
Confident 2.8 3.4=09
Content 2.6 3.4=09
Stressed 2.7 1.5=09
Sad 2.6 2.0=09
Frustrated 2.8 1.9=09
Irritated 2.6 1.7=09
Depressed 2.4 1.7=09
Anxious 2.4 1.5=09
Blue 2.4 1.7=09
Angry 2.1 1.6=09
Pessimistic 2.5 2.0=09
Attentive 3.1 3.5=09
Fatigued 3.2 2.4=09
Alert 3.0 3.6=09
Tired 3.3 2.6=09
Energetic 2.4 3.4=09
Sleepy 3.0 2.3=09

All pre-post differences, P < 0.001.

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