Edgar De Leon
3/29/2014
Writing 340 – Section 66822
Elizabeth Weiss
Assignment 3
Using Sensors to Monitor and Prevent Stress
Abstract: While many illnesses have seen vast reductions in their rates of occurrence, the rates
for mental illness have actually increased. New and existing sensors are being used to tackle this
growing problem. Electrodermal activity (EDA) is one type of sensor that monitors changes in the
eccrine sweat glands. These changes are correlated with EDA and provide data about a user’s
sympathetic nervous system which is known to activate the fight or flight response. EDA sensors
are being incorporated with other sensors in wearable devices that use the data tracked by the
sensors to suggest behaviors that improve mood and decrease stress. In another approach to the
problem, the sensors in a user’s phone are used to provide information about the user’s mood and
mental state. Both approaches allow researchers and doctors to reveal previously unobservable
trends concerning a user’s anxiety triggers.
About the Author:
Edgar was a junior majoring in Industrial and Systems Engineering with a minor in Business
Finance. He is looking forward to starting a career in venture capitalism and returning to school
to pursue an MBA with a specialization in Entrepreneurship or Business Analytics.
Introduction
Technology has improved many aspects of our daily lives but our individual stress has
actually increased. In the last decade, Americans were faced with two wars, the worst recession
since the Great Depression, and countless other worries that have negatively affected our jobs,
health, relationships, and sleep. It is no surprise that the number of people with mental illnesses
has increased dramatically. Mental illnesses are defined by the National Alliance on Mental
Illness as medical conditions that disrupt a person’s thinking, feeling, mood, and ability to relate
to others and daily functioning [12]. Serious mental illnesses include depression, schizophrenia,
bipolar disorder, obsessive compulsive disorder, post-traumatic stress disorder and borderline
personality disorder [12]. Mental illnesses affect people of any age, race, religion, or income.
According to the National Institute of Mental Health, there were 43.7 million adults aged
18 or older in 2012 with any mental illness and 9.6 million adults with a serious mental illness
[1]. In 2012, 2.7 million adults made suicide plans in the past year, and 1.3 million adults
attempted suicide in the past year [1]. In addition, mental health care costs increased from 35.2
billion dollars in 1996 to 57.5 billion in 2006 [2]. This made mental health care expenditures the
third most costly medical condition, behind heart conditions and trauma and tied with cancer [2].
Sensors are devices that detect or measure a physical property and record, indicate, or
respond to it. Wearable sensors have been increasing in popularity in the past few years and are
being developed to provide better treatment for the stress associated with mental illnesses.
Sensors can monitor physiological responses that detect emotion and mood, such as stress and
burnout in employment situations, and post-traumatic stress disorder (PTSD) in people
experiencing trauma [3]. Wearable sensors and the data they provide have the potential to halt
the increasing rates of mental illness and the associated total direct and indirect costs.
A Therapist in Your Pocket
Sensors have been used for many years in costly research studies and have been underutilized due to a lack of simplicity, bad design, cost, and lack of positive incentives in the
healthcare system [3]. The Northwestern University Center for Behavioral Intervention
Technologies (CBIT) is developing a smartphone application called Mobilyze that uses the
existing sensors in a user’s phone to track data about the user’s daily habits [4]. The phone tracks
whether you have made phone calls, received emails, or are at home ruminating for hours [4].
Mobilyze will send the user a suggestion to call or see friends. The purpose of the application is
to promote people to increase behaviors that are pleasurable and rewarding and will improve the
wearer’s mood [4]. In a small pilot study, Mobilyze was shown to reduce symptoms of
depression in the study’s participants [4]. Mobilyze demonstrates how our phones and other
mobile devices can provide useful information about our behaviors and mental state. Users also
avoid buying obtrusive and costly sensors by using the sensors in devices they already use.
Doctors and others individuals in the healthcare industry would be able to use this method of
data gathering to provide better and more personalized care.
EDA Sensor Technology
While Mobilyze uses sensors to track measurers such as location and phone use to
indirectly make observations about a user’s mental state, electodermal activity (EDA) is a more
direct technology that tracks stress at it physiological source. The study of the electrical changes
in human skin began over 100 years ago and has become one of the most frequently used
biosignals in psychophysiology or the branch of psychology that is concerned with the
physiological bases of psychological processes [5]. EDA was first introduced as a common term
for all electrical phenomena in skin, including all active and passive electrical properties which
can be traced back to the skin and its appendages [5].
Recently, there have been advances in the instruments used in EDA and there is a better
understanding of the underlying principles of EDA [5]. Changes in EDA can occur as a result of
a variety of sensory and psychological stimuli and typically are described in terms of an
immediate phasic change often termed the skin conductance response (SCR) [6]. EDA first
involves directly recording endogenous skin potentials (SPs) that occur due to changes in a
user’s eccrine sweat glands [6]. Eccrine sweat glands are special types of sweat glands that are
mostly concentrated in the palms of the hands and highly associated with EDA [6]. The
sympathetic sudomotor nerve endings in the hand cause the release of acetylcholine, a type of
neurotransmitter, that then causes sweating in the palm [6]. This all occurs when an individual is
stressed or anxious. As shown in Figure 1, the eccrine sweat glands can be modeled as an array
of variable resistors in parallel [6]. EDA takes advantage of this model by creating a device that
records the SPs.
Fig. 1: The eccrine sweat glands are equivalent to this
electrical model made up of an array of variable resistors
connected in parallel
(http://onlinelibrary.wiley.com.libproxy.usc.edu/doi/10.1111/j.16015215.2007.00247.x/full)
An EDA machine has to be carefully applied before it is ready for use.
Silver/silver chloride electrodes are carefully placed on the palmar surface of the hands,
specifically to the index and middle fingers of the nondominant hand where the eccrine sweat
glands are located [6]. The electrodes are paired with specially made electrolytes in the form of a
gel that together form part of an input circuit that is supplied by a constant voltage through the
EDA device [6].
The skin comes into contact with the conductive material. A person that is stressed will
have high levels of sweating from the eccrine sweat glands. This increases the conductivity of
the circuit and leads to SCR, which is expressed in units called microsiemens [6]. The EDA
process makes it easy to measure skin conductance. However, interpreting the data recorded by
the sensors and expanding the technology out of the research lab and into the hands of consumers
is much more difficult.
Wearable Devices Monitor Stress
Researchers have attempted to interpret the recorded SCRs with respect to
different emotions a user might be experiencing. EDA is frequently used in studies involving
people with depression, anxiety, schizophrenia, hypertension, and diabetes. However,
researchers in the past have been limited to studying patients in labs during short sessions. In
2010, a team of MIT researchers created a portable version of an EDA sensor. The sensor
included a flash memory card for data logging, a radio transceiver for wirelessly transmitting
data to a remote site, and an analog signal processor for data processing [7]. In addition, the
EDA sensor differed from traditional sensors used by researchers by using the ventral side of the
distal forearm as the recording site instead of the palmar surface of the index and middle fingers
[7]. The EDA sensor is attached to a comfortable wristband that allows the user to wear the
device for extensive periods of time [7]. The device allows researchers and doctors to potentially
reveal previously unobservable trends concerning a user’s anxiety triggers. Researchers can also
map these trends by location and can see “hotspots” of stress in real time. The MIT team created
a study that revealed a strong correlation between the proposed sensor wristband and an FDA
approved EDA measurement system. This means that the wearable sensor works just as
effectively as traditional EDA machines used by researchers.
Fig. 2: EDA sensor module developed at the MIT Media Lab
(http://web.media.mit.edu/~zher/eda.html)
The EDA technology created by the MIT researchers is already being incorporated into
new wearable devices. In 2010, Affectiva created and sold an improved version of the sensor
developed at MIT which they called the “Q Sensor” [8]. In addition to skin conductance, the Q
Sensor is also able to sense temperature and 3-axis accelerometer data [8]. It can log months of
data at a time. While the Q Sensor has since been discontinued, a company called Neumitra is
developing its own EDA wearable device called Bandu that also records skin temperature and
skin conductance; a consumer version is already available although it is still very costly [9]. It
records data from the sensors and sends it to the wearer’s smartphone. Like Mobilyze, Bandu
suggests behaviors to the user such as to take their medication, call a loved one, or listen to a
song [9]. Robert Goldberg, a neuroscientist and Neumitra founder, has been motivated by the
state of mental health in the U.S. He points to the startling rates of mental disorders. Goldberg’s
company was inspired in part by a war veteran who was having anxiety attacks. The Q Sensor
and Bandu have the ability to help many individuals such as returning soldiers with PTSD,
individuals with mental illness, and individuals with other illnesses such as diabetes to cope with
stress and to alert both the user and their doctors of trigger points.
Fig. 3: The Bandu wearable sensor measures skin temperature and conductance
associated with stress and excitement. It also relays messages to the wearer.
(http://www.technologyreview.com/news/508716/wrist-sensor-tells-you-how-stressedout-you-are/)
Do Users Benefit from the Data?
In addition, there are still many questions concerning the effectiveness of the sensors and
the data they provide. As with other sensors already on the market, the important question is
whether the surrogate measures they track are actually meaningful [10]. Will users benefit from
the increased information about their stress levels and change their habits or will they respond
with increased depression and anxiety? The Heart eHeart study will try to answer this question
by testing the effectiveness of mobile health devices and apps; it includes a planned 1 million
participants [10]. A sub study will compare outcomes and lifestyle changes for participants given
a bundle of devices that includes a Bluetooth blood pressure cuff, a scale, and a smartphone app
for their diet and heart monitor [10]. The study will provide insights into the effectiveness of
current wearable devices and health monitoring apps. However, the EDA wearable devices and
the Mobilyze app differ from the devices used in the study because they also provide feedback to
the user. However, whether users benefit from this feedback and are more likely to make
changes in their lifestyle has yet to be proven.
Data Security and Privacy
The security of the data logged by the sensors is another cause for concern for users of
the wearable devices and data tracking apps such as Mobilyze. Users want to know who is
monitoring their personal health data, and what they are doing with this information [3].
Rosalind Picard, with the use of the Affectiva Q Sensor, has observed changes in stress and
physiological responses in users who were shown movie trailers and other forms of digital media
[11]. It is possible to determine the instances in a video or other form of digital media that trigger
the largest and lowest physiological response in the viewers. Using this technique, marketers and
companies can make better products but they can also take advantage of customers’ stress
responses to entice them to buy a product by showing the user custom commercials, trailers, and
ads. Apple has already filed a patent application detailing ways of collecting mood-associated
data to deliver better targeted ads [13]. The proposed system gathers the data from body sensors,
user habits, and consumed data [13]. It effectively uses the data tracking of Mobilyze and the
physiological response tracking of devices such as the Q Sensor and Bandu for commercial
purposes. Further, data provided by the sensors can be used by employers to screen out
candidates with anxiety and other mood disorders if they were given access to the data. In effect,
employers and the countless other services that we all require such as healthcare and insurance
could discriminate against users with high stress levels as recorded by the sensors. Will wearable
device users be able to determine who has access to their data or will the companies developing
the devices share the data with private companies and marketers that allow them to take
advantage of users? These are legitimate questions for both regular users of wearable devices as
well as those with mental disorders and other illnesses.
Conclusion
The rising levels of stress and the direct and indirect costs associated with it has resulted
in a drastic change in the mindset of Americans and humans globally concerning triggers of
stress and things we might do to reduce and prevent stress. We are now more conscious about
how our diets, exercise, relationships, and actions affect our stress at any given moment and how
it relates to our moods than ever before. Wearable sensors are slowly becoming part of the
mainstream culture. Deloitte predicts a US market for wireless health monitoring devices of $22
billion by 2015 [3]. This number is surely to grow as companies such as Google and Apple come
out with products of their own. These devices have great potential to help slow the high rates of
mental illness if used correctly and if the data they track is secure. People with mental illness
suffer from elevated levels of stress on a daily basis. Wearable devices have the ability to give
users more personalized suggestions and greater peace of mind. In addition, the data they provide
can result in decreased healthcare costs, increased productivity, and would save many lives as a
result of better prevention, detection, and diagnosis of depression and other mental illnesses.
References
[1] Substance Abuse and Mental Health Services Administration, “Results from the 2012
National Survey on Drug Use and Health: Mental Health Findings,” SAMHSA NSDUH,
Rockville, MD, SMA 13-4805, Stat. Rep., Dec. 2013.
[2] “Total Expenditures for the Five Most Costly Medical Conditions,” NIMH, Jun. 2006.
[Online]. Available: http://www.nimh.nih.gov/Statistics/4TOT_MC9606.shtml.
[3] J.S. Kahn, “Making Sense of Sensors: How New Technologies Can Change Patient Care, ”
CHCF, Feb. 2013. [Online]. Available: http://www.chcf.org/publications/2013/02/making-sensesensors.
[4] M. Paul. “A Therapist in Your Pocket.” Northwestern University [Online] Available:
http://www.northwestern.edu/newscenter/stories/2012/02/therapist-phone-mohr.html.
[5] W. Boucsein, “Principles of Electrodermal Phenomena,” in Electrodermal Activity, 2nd ed.
New York, NY, S2012, ch. 1, sec. 1, pp. 1-2.
[6] J. Lagopoulos, “Electrodermal Activity,” Acta Neuropsychiatrica, vol. 19, iss. 5, Oct. 2007,
pp. 316-317.
[7] M. Z. Poh, N. C. Swenson, and R. W. Picard, “A Wearable Sensor for Unobtrusive, LongTerm Assessment of Electrodermal Activity,” IEEE Trans. Biomedical Eng., vol. 57, no. 5, May
2010.
[8] R. W. Picard. “What’s next for the Q Sensor?” MIT [Online]. Available:
http://affect.media.mit.edu/projectpages/iCalm/iCalm-2-Q.html.
[9] D. Talbot. (2012, Dec. 20). “Wrist Sensor Tells You How Stressed Out You Are.” MIT
Technology Review [Online]. Available: http://www.technologyreview.com/news/508716/wristsensor-tells-you-how-stressed-out-you-are/.
[10] C. Phend. (2014, Feb. 13). “Digital Health Devices Running on Questions.” MedPage
Today [Online]. Available: http://www.medpagetoday.com/Cardiology/Prevention/44294.
[11] R. W. Picard. (2011, Jun 11). Rosalind Picard: Emotion Technology. TEDxSF [Online].
Available: http://www.youtube.com/watch?v=ujxriwApPP4.
[12] “What is Mental Illness: Mental Illness Facts,” NAMI. [Online] Available:
http://www.nami.org/template.cfm?section=about_mental_illness.
[13] “Apple Wants To Measure Your Mood, then Send You Targeted Ads,” Fast Company.
[Online] Available: http://www.fastcompany.com/3025405/fast-feed/apple-wants-to-measureyour-mood-then-send-you-targeted-ads.