While many animals shed tears reflexively, scientists generally agree that only humans cry in response to our emotions. But why we cry remains a mystery.

Charles Darwin once said that emotional tears were “purposeless” from an evolutionary point of view, but recent research reveals that there may be a good reason why we do it.

Let it all out

We have three types of tears, and each serves a different purpose. Basal tears are the ever-present ones that keep our eyes from drying out. Reflex tears are the ones we shed in response to irritants like when we’re chopping onions. And then there are emotional tears. These tears are released when the cerebrum — a part of the brain associated with emotion — triggers the endocrine system to release hormones, which causes tears to form.

Unlike the other two types of tears, emotional tears don’t seem to bring us physical relief, which is why some scientists have hypothesized that they bring us emotional relief — hence the concept of “having a good cry.”

Biochemist William Frey suggested in the 1980s that crying relieves stress by ridding the body of stress-induced chemicals. He conducted a study comparing emotional tears to those shed in response to an irritant and found that emotional tears contain more proteins than non-emotional ones.

Around the same time he shared his findings, a study by Marquette University researcher Dr. Margaret Crepeau found that people with stress-related disorders, such as ulcers and colitis, cried less often than people without such disorders, seemingly affirming Frey's findings.

However, other scientists say the idea of a cathartic cry is overblown. Ad Vingerhoets, a professor at Tilburg University in the Netherlands, has tried twice to replicate Frey’s experiment without success.

Vingerhoets has conducted numerous other studies on crying, and he found that people tend to feel worse right after they cry. However, 90 minutes later, people who cried at a sad movie reported that they felt better than they did before the movie. They also felt better than their counterparts who didn’t cry.

“After the initial deterioration of mood following crying that is usually observed in laboratory studies, it takes some time for the mood not just to recover, but also to increase above the levels that it had before the emotional event,” he concluded.

Do we always feel better after we cry? Not necessarily.

Lauren Bylsma of the University of Pittsburgh says that “not all crying episodes are created equal.” She found that people are more likely to feel better after crying if they’re crying over something positive or if their crying leads to a new understanding of their situation. However, criers felt worse if they cried due to suffering or if they were ashamed of the act of crying.

Bylsma’s research also reveals that having witnesses to our tears can play an important role in how we feel about it. Criers who shed tears by themselves or in front of only one other person typically reported feeling better after, while those who cried in front of two or more people felt worse. In other words, crying in front of a friend is typically a more positive experience than tearing up in front of a group of people, such as coworkers.

woman comforting crying womanSometimes crying doesn't make us feel better, but it helps us bond to people around us. (Photo: Dragon Images/Shutterstock)

A cry for connection

While crying may not always leave us feeling better, scientists say there’s another reason why our emotional tears matter: They trigger bonding.

“Crying signals to yourself and other people that there’s some important problem that is at least temporarily beyond your ability to cope,” Jonathan Rottenberg, a psychology professor at the University of South Florida, told Time magazine.

There’s even evidence that emotional tears are chemically different from the other types of tears humans produce, and it’s been hypothesized that emotional tears are more viscous, making them more visible because they easily stick to the skin. In addition to signaling people that we need help, such tears may also aid in conflict resolution.

"We believe that tears convey helplessness and powerlessness, and that their function is to elicit help or stop aggressive behaviors in others," said Asmir Gračanin, Ph.D., one of Vingerhoets’ colleagues at Tilburg University.

In fact, tears are so important to bonding that people who don’t cry may be less socially connected. Psychologist Cord Benecke’s interviews with non-criers have revealed that such people experience more aggressive feelings and report less-connected relationships. They also have a tendency to withdraw from social interactions.

And an Utrecht University study found that 22 percent of people with Sjogren's syndrome — an autoimmune disease that makes it difficult to produce tears — have "significantly more difficulty" identifying their own feelings than people without it.

So it seems our tears do more for us than simply serve a biological purpose. “Tears are of extreme relevance for human nature,” according to Vingerhoets. “We cry because we need other people.”