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Why cry?

Alice,

I have always been curious about crying and tears. It seems so strange that when you are sad about something, salty water starts pouring out of your eyes! Do you know why this happens? Is it because our body needs some kind of release from the pain and has to let something go?

— Cindy

Dear Cindy,  

The question of why humans get teary-eyed dates far back, but as of yet, there’s no conclusive answer. Evolutionary biologist Charles Darwin made one of the earliest serious inquiries into the reason behind crying and concluded that it's all about muscle contractions. However, Darwin doesn't have the last word on this one. There are several theories linking biological, chemical, social, and psychological factors to why people cry. Despite any differences, most researchers agree that crying is a healthy and natural response in the human experience. What is known, however, is that there’s more to tears than meets the eye. It turns out that tears are made up of more than just salt and water, and the composition varies based on the reason for the tears.  

Before jumping into the reasons why people cry, it might be helpful to clarify how tears develop and what exactly is in them. Tears are continuously formed in the lacrimal glands above the eyes, coating the eyes while blinking to lubricate and shield them from foreign particles. While tears normally drain into the corners of the eyes (into the puncta), sometimes they overflow, which leads to the visible characteristic of crying. Regardless of whether tears are contained or are pouring out of your eyes, it turns out that they’re much more than “salty water!” In addition to salt and water, tears contain a host of proteins, carbohydrates, enzymes, and electrolytes. This chemical combination is distributed over three layers in a given tear:  

  • Inner mucus: helps the tears stick to the eye  
  • Middle watery layer: hydrates and prevents bacteria getting in  
  • Outer oily layer: allows the eye to see through the tear and prevents it from evaporating  

 Adapted from American Academy of Ophthalmology.  

 The complexities of tears don’t stop there. There are three types of tears — basal, reflex, and emotional — which contain slightly different compounds depending on their function. Basal tears are an everyday source of hydration and protection from irritants such as dirt. Reflex tears help the eyes to flush out bothersome environmental triggers, such as chemicals, smoke, and even onions. These tears tend to contain extra antibodies to attack bacteria. Emotional tears are the body’s natural response to a variety of emotions from sadness to anger, happiness, and fear. When the body senses an emotional response (in the limbic system), it triggers a part of the brain (called the pons) to prompt the lacrimal glands to generate emotional tears. These emotional tears consist of extra proteins and hormones, which some researchers believe is the result of the body releasing chemicals produced when stressed or upset. In fact, when researchers analyzed the difference between tears shed by people moved by a Hollywood tearjerker and tears sparked by cutting onions, they found that the tears from the weepy film contained different proteins. So "crying it all out" could literally mean crying those hormones out of your body.  

Another chemical theory is that crying helps to release endorphins (mood-elevating and pain-relieving chemicals) into the bloodstream. These chemical factors give credence to the assertion that most people feel physically better after having a good sob. In addition to releasing emotions, tears also help to convey emotions that may be difficult to verbalize. Tears emphasize facial expressions and can convey sadness or grief. In fact, in one study, researchers showed participants photographs of people weeping, some with the tears digitally removed. Participants had difficulty identifying the emotion being expressed by faces without the tears. Other researchers argue that crying is a form of emotional communication — they argue that it shows that your emotions are honest. For instance, it's notoriously difficult to fake sobbing, as many actors can tell you.  

In addition to the chemical theories, there are also socio-psychological theories of crying. The most obvious one stems from what’s known about newborns. Infants cry to resolve a negative situation: hunger, pain, a lack of attention. Perhaps people have held on to this tactic with age, and they weep in order to receive social support, which in turn makes them feel better about whatever is bothering them.   

While there are many potential explanations as to why people cry, there’s some consensus that crying seems to be uniquely human. No other animal expresses its emotions by releasing tears, not even human’s closest relatives, the apes. They cry vocally, much like screaming newborns, but they remain dry-eyed. Their tear ducts only kick into action when they've been physically injured. So, while you may never get the definitive answer on why you cry, you can still appreciate this distinctly human and emotionally cathartic experience. Hope this helps!  

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Last updated Jun 30, 2022
Originally published Mar 22, 2002

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