Since we’re the only species to cry tears of emotion, you’d think that we would have all the answers as to why we cry, right? Wrong. We don’t really know why we cry. Some people attribute it to an emotional response to life events; others say it was a way of communicating before the emergence of language. While there are some reasons for crying, like releasing toxins, killing bacteria, and relieving stress, one thing most people can agree on is that after a “good” cry, we feel better. Now, there is some research to backs up this train of thought.
Researchers from the University of Tilburg in the Netherlands brought together a group of people to watch a couple of movies generally considered to be tearjerkers. The participants watched these emotionally charged films (La vita è bella (Life is Beautiful) and Hachi: A Dog's Tale) and were asked how they felt before, immediately afterward, and then 20 and 90 minutes afterward.
Out of those 60 participants, 28 of them cried during the films, while the other 32 didn’t shed a tear. Those 32 said they felt the same way at the beginning of the film as well as immediately afterward, and also noted that their moods remained unchanged 20 and 90 minutes later. On the other hand, the people who cried during the films reported feeling lousy immediately after the credits rolled. Twenty minutes later, however, the criers reported that their moods had returned to the levels they reported before the films began. But then, after 90 minutes, the criers reported they were in even better moods than before the movie.
It's easy to suggest that there was a yo-yo effect in which the criers simply felt sad while watching the movie, and then returned to their original mood afterward — that they only believed they felt better before. However, it seems that over a longer period of time, these criers did indeed feel an uptick in happiness.
So why did the criers feel better after crying? Though the researchers couldn't explain, the criers might have felt better for a number of reasons. Previous studies have found crying reduces stress by releasing toxins through our tears. These tears are called emotional tears, and they are one of the three types of tears our body produces. It's possible these criers also felt better because crying has also been shown to cause the release of endorphins, our body's natural pain killer, thus making them feel better. So, although they had just watched two sad movies, the criers may have been releasing the toxins of a stressful day, and when combined with endorphins, it resulted in a much better mood.
Source: Graanin A, Vingerhoets A, Kardum I, et al. Why crying does and sometimes does not seem to alleviate mood: a quasi-experimental study. Motivation and Emotion. 2015.