This past week I discovered an interesting YouTube page that goes by the name of ASAPscience. They have a lot of really cool videos that provide summarized explanations about scientific phenomena. One such video that I stumbled upon and that fascinated me very much was about crying. Have you ever considered why we cry, and whether crying may serve a useful purpose? Before I begin describing the research and information that I gathered, it is important to note that a common statement I ran across is that much of the information surrounding this topic is inconclusive and ought to be explored further, as is the case with much scientific literature. Despite this fact, I still ran across some very interesting articles that provide plausible explanations as to why we cry!
Firstly, it is worth noting that there are three kinds of tears that our body releases: basal, reflex, and emotional. This post will be focusing on emotional tears, but it is important to outline the other two types of tears. Basal tears serve to lubricate the eyes, keeping them from drying out, whereas reflex tears act in response to harsh irritants, such as dust, onions, or smoke. So what then, is the purpose of emotional tears?
Researchers have found that reflex tears and emotional tears have very different compositions; reflex tears are comprised mostly of water (about 98% H2O), while emotional tears have higher levels of chemicals such as prolactin, adrenocorticotropic hormones (ACTH) and leucine-enkephalin. ACTH, secreted and produced by the anterior pituitary gland, is often produced in response to biological stress. Leucine-enkephalin is an endorphin that reduces pain and works to improve mood. Although research in this area is fairly limited, one theory related to the above findings suggests that crying is one of our body’s mechanisms to literally shed stress.
So, if you ever find yourself crying of heartbreak, thank your romantic (or ex-romantic) other for inducing your body’s natural stress-detox system (Although there are clearly more profound conclusions to be drawn from this literature!).
Last but not least:
Most interestingly (to me at least), is the presence of prolactin in emotional tears, which is a hormone released from the anterior pituitary gland that stimulates milk production after childbirth. One can at least begin to draw inferences about the presence of the other chemicals in emotional tears, but what about prolactin? This got me to do some further research and I discovered that these findings have some pretty significant implications regarding gender differences. Clearly, men and women are biologically different in a number of ways. It’s fascinating to examine how the circulation of particular hormones (normally well regulated by our bodies) manifests itself, esp. with regard to sex differences. If this particular aspect of the literature fascinates you, I suggest you take a look at the following article: http://scienceblogs.com/observations/2011/01/08/why-do-women-cry-obviously-its/ which outlines some effects of male and female hormones and their relevance to emotional expression.
Additional sources:
Howstuffworks.com: http://www.youtube.com/watch?v=QGdHJSIr1Z0
ASAPscience YouTube video: http://www.youtube.com/watch?v=QGdHJSIr1Z0
On Psychology and Neuroscience 
This was a fascinating post. Interestingly enough I have been having similar thoughts myself about the purpose of crying. It has always mystified me why it is such a natural reflex to cry under moments of extreme emotional stress, and the fact that almost everybody feels much better after a good cry must shed some light on its detoxifying properties. Is it possible that the biochemical substrates for emotion, and how they physiologically impact our physical body, are the same ones being released through emotional tears? In this case, maybe leucine-enkephalin is released to reward the behavior of detoxifying the body through crying, while ACTH could be the actual stress substrate in peripheral neurons responsible for the subjective experience of emotional pain prior to crying. Prolactin, then, might be a hormone responsible for eliciting social support and empathy during a period of emotional release, because we all know that crying can draw a friend to give their support. Looking forward, I am especially curious about how the body and brain coordinate hormonally and neurochemically to provide differentiation for the various types and degrees of emotional experience; how does our mind-body complex create a different subjective experience of the emotions joy, relaxation, surprise, fear, sadness, shame, guilt, etc.?
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I thought this post was really interesting and relevant to everyday life. It’s common, at least for me, to cry when I’m frustrated, stressed, sad, etc, so knowing the different chemical compositions of tears makes sense as to why there’s certain chemicals in sad tears. However I wonder if happy tears would have a different chemical composition than the other types of tears. Could it be that there’s more leucine-enkephalin in happy since that helps improve mood, or would there be a different composition altogether?
Since prolactin is useful in “establishing and maintaining relationships”, I can see how Brian thinks that it could be “responsible for eliciting social support and empathy during a period of emotional release.” I wonder if the chemical levels differ between men and women’s tears for prolactin. Would there be a higher amount in woman since prolactin is also a hormone that stimulates milk production? And in what ways does prolactin affect men and woman?
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