Walking Sugiyama, Leslie, Giles-Corti, & Owen, 2008).

Walking
twice a week in the botanical gardens proved to be practical and easy to fit in
to the routine, as evidenced by the adherence to the protocol. While we were
not able to show an effect for this intervention, it is possible that walking
in the botanical gardens had an effect on other well-being measures that were
not tested here. The low cost and ease of the intervention is well suited for international
doctoral students, therefore more research is needed to understand whether this
stress-management intervention can be effectively tailored to suit the needs of
this population.

There
are some limitations to this study. First, we were only able to employ a single
participant. However, single subject experiments are robust when the magnitude
of the effect is great and within subject comparisons are allowed (Nock, 2007). Second, other
historical explanations could account for the pattern of responses in perceived
academic stress and HRV, such as the student becoming more habituated to
doctoral level coursework and being able to more consistently manage its
associated challenges. Finally, while no guidelines exist for the PAS scale
regarding normative scores, or cut off ranges for high, medium or low stress
levels, the HR and HRV measurements at baseline are within normal range. This
points to the possibility that the student was not significantly stressed to
begin with, and therefore the intervention may have had an effect on a student
experiencing higher levels of stress. However, our measurement of academic
stress specifically and not stress in general allowed us to focus on a specific
source of stress, and we also used an objective measure for heart rate
variability which adds internal validity to our design.

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            A number of studies also suggest that walking in natural
environments in groups has a beneficial effect on physical and mental health (Ekkekakis et al., 2000; Sugiyama, Leslie,
Giles-Corti, & Owen, 2008). It is possible that the same
intervention would have shown greater impact had it included a social component
by instructing the participant to walk with another person. It is also possible
that the effects on shinrin-yoku are not persistent, and changes in perceived
stress or heart rate variability are short-lived as suggested by prior research
(Ekkekakis et al., 2000). Finally, some of
the prior studies also report mixed findings regarding cardiac measures such as
blood pressure (Bowler et al., 2010; Sung et al., 2012), which may explain our negative
findings for heart rate and heart rate variability.

There
are different explanations of why this intervention may not have had a
significant effect. Prior interventions on “chronically stressed” adults are
done by recruiting subjects that are deemed to be stressed at baseline (Morita et al., 2007), where those reporting the highest
levels of stress pre-intervention report the largest beneficial gains. It is
possible that our subject was not significantly stressed pre-intervention.
Because our measure for perceived academic stress did not contain normative
data suggesting whether the scores obtained represent high or low stress levels,
it is difficult to state whether the participant was stressed at the beginning
of the intervention. Given the small variation during baseline and intervention
phases, it is just as likely that our subject was either consistently stressed
or not stressed the entire period. However, the HRV rates are within normal
guidelines and suggest good adaptation to stress. These levels suggest that our
subject was not stressed at the beginning of the study. It is possible that
shinrin-yoku is more effective when participants are already experiencing high
levels of stress at baseline. Therefore, it is possible that our student was
not significantly stressed pre-intervention, and the intervention may have had
an effect on a student experiencing higher levels of stress.

We
did not find a significant effect of walking in botanical gardens twice a week
on perceived academic stress, heart rate, or heart rate variability in a
doctoral student. No clear patterns emerged for perceived academic stress or
heart rate across the intervention and baseline periods, or on the intervention
days. It is notable that there was a trend in heart rate variability in line
with our hypothesis that the intervention would increase help better adjust to
stress, however the magnitude of the trend is not significant.

Discussion

 

 

Variable

Mean
BL 1

Mean
INT 1

Mean
BL 2

Mean
INT 2

Stress
scale score

3.7

3.8

3.9

3.8

Heart
rate

72.4

72.6

73.1

71.0

HRV
Composite Score

662.2

690.6

683.2

699.7

Figure 4. Means of main
outcome by study phase

 

Stars represent days
on which the intervention took place

Figure 3. Effect of
intervention on Composite Heart Rate Variability

 

Stars represent days
on which the intervention took place

Figure 2. Effect of
intervention on heart rate

 

 

Stars represent days
on which the intervention took place

Figure 1. Effect of
intervention on perceived academic stress

 

Data
representing the composite daily scores for heart rate variability over the
two-month period are presented in Fig. 3. The figure depicts the score obtained
from the HRV composite score for every day of the study. Visual inspection of
the data does not suggest a marked treatment effect of the intervention on HRV
as measured by this tool. Figure 4 shows there is a difference in means (mean
BL1=662.2, mean INT1=690.6, mean BL2=683.2, mean INT2=699.7), with higher means
on intervention periods. This suggests better adjustment to stress over
intervention periods. It is important to note however that it is unclear
whether these small changes represent a clinically meaningful change, and
visual inspection does not allow to make out this trend as clearly.

Composite
heart rate variability

Data
representing the daily measurement of heart rate over the two-month period are
presented in Fig. 2. The figure depicts the result obtained from heart rate measurements
for every day of the study. The means in Table 1 also show no significant
change (mean BL1=72.4, mean INT1=72.6, mean BL2=73.1, mean INT2=71.0). Visual
inspection of the data does not suggest a marked treatment effect of the
intervention on heart rate. A resting heart rate between 50 and 80 bpm is
considered within normal range – with heart rates above 80 bpm associated with
greater morbidity (Shigetoh et al., 2009) -, and so these results show it has
remained stable throughout the study period.

Heart
rate

Data
representing the daily scores of the Perceived Academic Stress Scale over the
two-month period are presented in Fig. 1. The figure depicts the score obtained
from the self-report scale for every day of the study. Visual inspection of the
data does not suggest a marked treatment effect of the intervention on
perceived academic stress as measured by this scale. Figure 4 shows there is a
difference in means (mean BL1=3.7, mean INT1=3.8, mean BL2=3.9, mean INT2=3.8) suggesting
levels of perceived academic stress were highest at the beginning of the study,
during the first baseline period, and then decreased during the first
intervention period. However, the mean during the second intervention period
does not support the hypothesis that the intervention reduces perceived
academic stress. Furthermore, it is unclear whether these small changes represent
a clinically meaningful change, and visual inspection does not allow to make
out this trend as clearly.

Perceived
Academic Stress

Results

 

A
reversal design (ABAB) was used. During both intervention phases, the
participant took hour-long walks at a leisurely pace through the Brooklyn
Botanical Gardens, twice a week (Tuesdays and Saturdays). During the walk, the
subject did not carry her cell phone to ensure no distractions would take place
for the duration of the activity, and ensure a mindful immersion using all
senses, as suggested by the practice of shinrin-yoku. No walks in gardens took
place during both baseline periods. Each phase spanned 14 days each.

Experimental
design and conditions

Mobile devices are increasingly being used to track heart
rate and HRV (Ozdalga, Ozdalga, &
Ahuja, 2012). Phone applications allow for a mobile version of pulse
oximeters, where infrared light is used to determine oxygenated and
deoxygenated blood based on the blood opacity. The camera contained in smart
phones contains a light that allows for the measurement of variable levels of
opacity through the pulsating capillary tissue beneath the surface of the
finger. Using this technology, applications translate these into commonly used
ECG vectors, converting the data into beats per minute. Smartphone applications
measuring HRV have been found to accurately detect ranges of HR across individuals
(Gregoski et al., 2012). The Kenkou Stress App was used to measure
heart rate and heart rate variability. Measurement was done at different times
of the day throughout the study period, as suggested by the application’s
guidelines. The application prompts the user to ensure there are no
distractions and to look for a calm environment, to breathe deeply and calmly, keeping
movements of the finger and phone as low as possible while measuring. The user
then has to press their finger on the lens of the camera, while in a seated
position. The composite score of HRV produced is determined by the heart’s
beat-to-beat intervals. Based on this data, the application calculates an RMSSD
score (rhythmic variability of the heart), an AVG RR-interval (Average
Wave-to-wave interval between adjacent heart beats), and the PNN50 (percentage
of beat-to-beat intervals that vary more than 50ms in comparison with the
previous interval). The resulting composite score reflects overall variability.
Higher scores suggest better adjustment to stress.

Heart
rate variability is commonly used in clinical settings as a noninvasive
indicator of cardiac autonomic modulation. A lower HRV has been found to be
associated with poorer health outcomes, and overall increased morbidity and
mortality (Tsuji et al., 1994). HRV is a measure of autonomic modulation of heart rate
used as both a prognostic and a diagnostic tool (Fei, Copie, Malik, &
Camm, 1996). It has been proposed that heart rate
variability (HRV) may provide an index of the degree to which the brain’s
“integrative” system for adaptive regulation provides flexible control over the
periphery, capturing the capacity of an organism to adapt and function
effectively within a complex environment. If this is the case, then HRV may
provide a useful index of stress (Thayer, Åhs, Fredrikson, Sollers, & Wager, 2012)

Heart
rate and HRV variability composite score

The
Perception of Academic Stress (PAS) scale (Bedewy & Gabriel, 2015) is a brief
self-report scale to measure students’ perceptions of academic stress and its
sources. It consists of 18 items rated on a 5-point Likert-type scale (from
1?=?strongly disagree to 5?=?strongly agree) of students’ perceptions and
experiences in three domains: academic expectations, workload and examinations,
and students’ academic self-perceptions. It takes approximately 5 minutes to
complete. Lower scores reflect higher levels of perceived academic stress.
There is acceptable internal consistency reliability (0.7), and there is
evidence for face, content, and convergent validity of this instrument (Bedewy & Gabriel, 2015). The PAS was
administered every day between 7 and 9 am.

Academic
stress scale

Measures

 

The
participant was a 34-year old international doctoral student at the City
University of New York, during the first year of her PhD in Clinical Psychology.
No current heart conditions were reported.

Participant
description

Methods

 

The
purpose of this paper was to study the effects of a shinrin-yoku adaptation to
an urban botanical garden as an effective stress management intervention for an
international doctoral student in the first year of a clinical psychology PhD.

Research
on shinrin-yoku on university students has showed great promise. Yamaguchi et
al. (2006) examined the effectiveness of shinrin-yoku and walking on the stress
levels of young university students, as measured by circadian rhythms on
salivary amylase activity as an indicator of an individual’s stress levels in a
forest environment, and found that the forest was a good environment in which
people could experience much less environment-derived stress based on the
levels observed (Yamaguchi, Deguchi, & Miyazaki, 2006). The effect of outdoor walking on
the stress levels of students has also been found to be consistent across
settings as reported by Plante et al. (2006), who explored the effects of 20-minute
periods of exercising by comparing a brisk outdoor walk around a college
campus, walking on a laboratory treadmill combined with a virtual reality video
presentation of the same college campus walk, or viewing the virtual reality
walk without participating in any actual exercise. The authors concluded that
participants walking in the laboratory with the virtual reality were more
relaxed and experienced the least tension of the three conditions; exercising
outside was the most enjoyable and the most energizing. (Plante, Cage, Clements, & Stover, 2006).

Prior
research has been done applying the practice of shinrin-yoku to urban botanical
gardens for stress management. Kohlleppel et al. (2002) explored the effects of
visits to botanical garden in Florida on depression and perceived stress, and
found that visiting a botanical garden was an important coping strategy even
when controlling for other covariates, explaining almost 30% of the observed
variance in depression scores and a smaller yet significant reduction in
perceived stress (Kohlleppel, Bradley, & Jacob, 2002). Walking and
running in natural environments, such as public parks and green university
campuses, have been found to systematically lead to greater benefits in
attention, and positive emotions as compared to groups exercising in synthetic
environments, such as indoor and outdoor built environments. (Bowler, Buyung-Ali, Knight, & Pullin, 2010).

Shinrin-yoku
or “forest-air bathing” is a common practice in Japan, that entails immersing
oneself in nature by mindfully using all five senses (Hansen, Jones, & Tocchini, 2017). A recent systematic
review on shinrin-yoku found robust effects for this practice on various
biological measures usually linked to stress, such as heart rate (HR), heart
rate variability (HRV), salivary cortisol levels and immunoglobulin, in research
studies conducted across different countries around the world (Hansen et al., 2017). Shinrin-yoku has
been found to decrease hostility and depressed mood in a large sample of
chronically stressed young adults after participating in shinrin-yoku compared
with themselves on a control day, and this effect was still significant after
accounting for the conditions of the forest visit such as duration of stay (Morita et al., 2007). Shinrin-yoku programs have also
been tailored as cognitive behavior therapy (CBT)-based intervention programs
using forest environments, where the forest therapy groups are found to have
greater reductions in stress-relevant markers such as salivary cortisol levels
and self-reported quality of life (Sung, Woo, Kim, Lim, & Chung, 2012).

Natural
environments have also been found to have beneficial health effects. Evidence
for how contact with the natural environment can promote good health comes from
studies in a variety of disciplines such as psychology, environmental health,
ecology, horticulture, landscape planning, leisure and recreation, public
health, policy and medicine (Pretty et al., 2007). Access to green
space has been associated with longevity and decreased risk of mental
ill-health in Japan, Scandinavia and the Netherlands (Pretty et al., 2007). A study in the
UK found that the experience of nature enhances self-esteem and improves total
mood disturbances across 10 “green exercise” activities, including walking,
cycling, horse riding, fishing, canal-boating and conservation activities (Pretty et al., 2007). A prior study
reports restorative effects on cognitive function to occur at higher rates in
natural versus urban environments (Berman, Jonides, & Kaplan, 2008). The authors based their hypothesis
on attention restoration theory, which provides an analysis of the kinds of
environments that lead to improvements in directed-attention abilities. Nature,
due to being filled with “intriguing” (understood as novel and uncertain)
stimuli, grabs attention in a bottom-up manner, allowing top-down
directed-attention abilities a chance to replenish (Berman et al., 2008). Another study found a dose-response
relationship in the association between duration, frequency and intensity of
exposure to nature and health in an urban population, whereas people who made
long visits to green spaces had lower rates of depression and high blood
pressure, and those who visited more frequently had greater social cohesion (Shanahan et al., 2016).

The
health benefits of walking are well established (Hardman & Morris, 1998). Walking is
beneficial because of improved fitness, it is a convenient activity that can be
easily accommodated around domestic and occupational routines, and is sustainable
year round thanks to its self-reinforcing and habit-forming qualities (Hardman & Morris, 1998). Walking has been
proven to have a significant impact on affect (as measured in valence and
arousal dimensions) even when done in short bouts, when it is performed
outdoors and integrated into the participants’ daily routines, resulting in
shifts towards higher activation and improved affective valence (Ekkekakis, Hall, VanLanduyt, & Petruzzello, 2000). A systematic
review on the health effects of walking reported anxiolytic and antidepressant
effects, and reductions in the physiological, cardiovascular and catecholamine
reactivity to stress (Hardman & Morris, 1998).

There
is increasing concern about stress and well-being among PhD students, with
recent studies reporting that 32% of them are at risk for psychiatric disorders,
especially depression, compared to other highly education populations (Levecque, Anseel, De Beuckelaer, Van der Heyden,
& Gisle, 2017). International
students, who make up 5% of clinical psychology PhD programs (Association, 2009), face added
burdens such as acculturation stress and integration with domestic students,
which can result in significant psychological stress (Chen, 1999). Therefore, research
and development of efficient and effective stress management interventions for
international doctoral students is necessary.

Introduction

 

 

 

 

 

 

 

 

 

 

Doctoral
Program in Health Psychology and Clinical Science, The Graduate Center, City
University of New York

Irina
Mindlis

 

An
urban adaptation of shinrin-yoku for stress management

 

 

 

 

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