Teary Facts About the Science of
Crying
March 12, 2016
Story at-a-glance
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Humans are the only animals that shed tears of
emotion
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Shedding tears may be a way to heighten the facial
appearance of sadness, thereby providing a survival
advantage
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Tears contain nerve growth factor (NGF), which is a
neuropeptide that plays a role in the development
and survival of neurons
By Dr. Mercola
While many animals "cry" by making vocalizations as emotional
expressions or sounds of pain, humans are the only animals that
shed tears.
Your tears may be happy or sad, or they may be described
clinically as lacrimation, particularly to describe the flow of
tears that may occur when you cut an onion or get a few grains
of sand in your eyes.
No matter the cause of your tears, the scientific process
that turns on the "waterworks" is the same. You have a lacrimal
gland located between your eyeball and eyelid, which produces
tears documented as emotion-related.
When you blink, the fluid gets dispersed over your eye, then
drains via your lacrimal punctum (and ultimately through your
nose, which is why crying makes your nose run). If your tears
are voluminous, however, they will overflow this drainage system
and cascade down your cheeks.1
The Three Types of Tears
Your body produces three different types of tears. There's
the basal variety, which are made as a form of lubrication and
protection for your eyes. These are constantly secreted in tiny
quantities (about one gram over a 24-hour period) and coat your
eyes when you blink.2
You also produce reflex tears. These are another form of
protection and are released in response to irritants, such as
wind, dust, smoke or cut onions. The third form of tears —
emotional or "psychic" tears as they're sometimes called — are
arguably the most talked about and the most mysterious.
Your psychic tears are produced in response to strong
emotions —
stress,
happiness, sadness, physical pain and more. These emotions
trigger tearing via an intricate connection with your autonomic
nervous system. As explained in The Independent:3
" … [T]here is an area of your brain specifically to
deal with your emotions, called the limbic system
(specifically the part of it called the hypothalamus), which
is hard-wired into your autonomic nervous system (that's the
part you don't have any control over).
This system, via a neurotransmitter called
acetylcholine, has a degree of control over the lacrimal
'tear' system; and it is this tiny molecule which then
stimulates tear production.
So in short, your emotional reaction … triggers your
nervous system, which in turn, orders your tear-producing
system to activate."
Crying Involves Many Physical Sensations
When you cry, it's not only a matter of tears streaming down
your face. It also typically involves an increase to your heart
rate. You may begin sweating and, often, a lump will form in
your throat, which is called the globus sensation. This isn't a
true lump, but rather is related to a strain in your throat
muscles.
When you cry, the opening in your throat that allows air to
pass from your larynx to your lungs (known as your glottis)
becomes enlarged.
When you swallow, your glottis closes, but when you cry your
body enlarges the glottis to let in more oxygen. It's this fight
between trying to open and close your glottis that leads to
muscle strain and the feeling of a lump in your throat.4
Crying as a Means of Displaying Submission or Vulnerability
Some have theorized that shedding tears is a way to heighten
the facial appearance of sadness, thereby providing a survival
advantage of sorts. It may, for instance, help you to solicit
support. As reported by the American Psychological Association
(APA):5
"'Tears add valence and nuance to the perception of
faces,' says the study's lead author, Robert R. Provine,
PhD, a professor of psychology and neuroscience at the
University of Maryland, Baltimore County.
Tears become a sort of social lubricant, he says,
helping to ensure the smooth functioning of a community by
helping people communicate."
Tearing up helps to build and strengthen personal
relationships because it signals to others that your defenses
are down, you're less of a threat and it may evoke feelings of
empathy in others. Researcher Oren Hasson, PhD explained:6
"My analysis suggests that by blurring vision, tears
lower defenses and reliably function as signals of
submission, a cry for help, and even in a mutual display of
attachment and as a group display of cohesion."
Do Tears Have Medicinal Properties?
Tears shed due to an emotional response contain a high
concentration of adrenocorticotropic hormone (ACTH) — a chemical
linked to stress.
One theory of why you cry when you're sad is that it helps
your body release some of these excess stress chemicals, thereby
helping you feel more calm and relaxed.
Tears also contain nerve growth factor (NGF), which is a
neuropeptide that plays a role in the development and survival
of neurons, particularly sensory neurons involved in
transmitting pain, temperature and touch.7
According to Provine:8
"Several lines of evidence suggest that the NGF in
tears has medicinal functions. The NGF concentration in
tears, cornea, and lacrimal glands increases after corneal
wounding, suggesting that NGF plays a part in healing.
More directly, the topical application of NGF
promotes the healing of corneal ulcers and may increase tear
production in dry eye … Although more of a scientific long
shot, I suggest that tears bearing NGF have an
anti-depressive effect that may modulate as well as signal
mood.
Non-emotional, healing tears may have originally
signaled trauma to the eyes, eliciting caregiving by tribe
members or inhibiting physical aggression by adversaries.
This primal signal may have later evolved through
ritualization to become a sign of emotional as well as
physical distress.
In this evolutionary scenario, the visual and
possibly chemical signals of emotional tears may be
secondary consequences of lacrimal secretions that
originally evolved in the service of ocular maintenance and
healing."
Four Interesting Facts About Crying
Why humans shed tears is still a question shrouded in
mystery, but there are some intriguing facts worth learning.
Mental Floss recently shared several of them:9
1. Crying (Eventually) Makes You Feel Better
Research published in Motivation and Emotion found crying
may lead to both worsened and heightened mood depending on
when your mood is measured.10
The research involved 60 people who watched an emotional
movie and had their moods assessed immediately after as well
as 20 and 90 minutes later. Those who cried during the film
had significantly increased negative moods right after while
non-criers' moods remained unchanged.
By the next measurement, the criers' moods had returned
to baseline but, interestingly, by the final measurement
their moods had not only recovered but also were
enhanced compared to their pre-film measurements. So
while crying might initially make you feel worse, it may
ultimately boost your mood. The researchers
explained:11
"After the initial deterioration of mood
following crying that was observed in laboratory
studies, it apparently takes some time for the mood, not
just to recover, but also to become even less negative
than before the emotional event, which corresponds to
the results of retrospective studies."
2. You Can Stop Onions From Making You Cry
Onions release a gas called lachrymatory factor (LF),
which causes tearing. Japanese researchers developed an
onion that lacked the enzyme necessary to produce LF, and
therefore wouldn't cause tearing, but it also altered the
beneficial sulfur-containing compounds in the onion.
So while the fact that onions make you tear up is a bit
inconvenient, it's also a reminder of the many potent health
compounds they contain. That being said, the World's
Healthiest Foods shared a few tips to cutting onions that
should help lessen eye irritation and tearing. If this is an
issue for you, don't give up on onions. Try these tips
instead:12
"Use a very sharp knife and always cut the onions
while standing; that way your eyes will be as far away
as possible. Consider cutting onions by an open window.
If cutting onions really makes you cry, consider wearing
glasses or goggles.
Chill the onions for an hour or so before
cutting; this practice can slow down the onion's
metabolism and thereby lessen the rate of LF gas
production.
Cutting onions under cold, running water is a
method that is often used to cut back on eye irritation,
but it's a method we view as a second-best choice since
some of the nutrients found in onion can be lost into
the flow of water."
3. Crying Might Help You Win a Negotiation
Expressing sadness, including crying, during a
negotiation might help you to get your way. This was true,
however, only when certain conditions were met, namely when
recipients:13
- Perceived the expresser as low power
- Anticipated a future interaction
- Construed the relationship as collaborative in
nature
- Believed that it was inappropriate to blame others
4. Crying After Sex Is Normal
Research suggests nearly half (46 percent) of women have
cried after sex at some point in their lifetime14
(and separate research suggests many men have cried after
sex as well). Known as postcoital dysphoria, or PCD, this
may be due to fluctuations in hormones that occur during and
after sex. It may also be due to the intimate nature of sex,
which allows people to express emotions they've been keeping
bottled up.
What Do Tears Look Like Under a Microscope?
In a project called "Topography of Tears," photographer
Rose-Lynn Fisher used a microscope to examine what dried human
tears look like close up. Over the course of several years, she
examined more than 100 tears from herself, volunteers and even a
newborn baby, under a microscope.
What resulted was a beautiful collection of strikingly
different images, many resembling large-scale landscapes. Fisher
described them as "aerial views of emotion terrain."15
She told Smithsonian magazine:16
" … Tears are the medium of our most primal language
in moments as unrelenting as death, as basic as hunger and
as complex as a rite of passage … It's as though each one of
our tears carries a microcosm of the collective human
experience, like one drop of an ocean."
As the saying goes, a picture is worth 1,000 words, so to see
the photos for yourself, see
Rose-Lynn Fisher's website.17
What is perhaps most intriguing is the different forms tears
take depending on the emotions behind the. Tears of "laughing
till I'm crying," tears of grief, tears of change, onion tears
and others all appear remarkably different.
© Copyright 1997-2016 Dr. Joseph Mercola. All Rights Reserved.
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