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Tears of joy stream from our eyes when we are overwhelmed by feelings of happiness, elation, or gratitude. Although crying is usually associated with distress, intensely positive experiences—such as receiving an award, a marriage proposal, or watching an emotional film—can also move us to tears. In essence, crying occurs when we become emotionally overwhelmed and our emotions exceed our capacity to contain them, even when they are positive.
Tears are the defining feature of crying. Our eyes continuously produce basal tears, which protect the eye's surface by keeping it moist and removing foreign particles. These basal tears typically drain into the nose unnoticed. Emotional crying, however, involves an increased production of tears—a phenomenon previously considered uniquely human.
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Tears are produced in the gland above the eyelid (left side of the illustration) and continuously drain into the nose via the ducts (right side)
(Illustration: BO VEISLAND / SCIENCE PHOTO LIBRARY)
However, a recent study challenges this assumption, showing that dogs produce more tears when reunited with their owners than when encountering other familiar individuals. Furthermore, crying includes more than just tears; it often involves sobbing sounds and irregular breathing, behaviors also observed in some animals. Nonetheless, crying remains a universal human experience, prompting researchers to ask: Why do we cry from happiness?
Crying is beneficial to us because it provides both emotional and physical relief. Our body constantly strives to return to its baseline state across physiological and emotional parameters. However, strong emotions—especially intense positive ones that bring us to tears—can disrupt this balance by increasing heart rate, blood pressure, and respiratory rate. These heightened physiological responses are regulated by the autonomic nervous system, which consists of two opposing subsystems: the sympathetic and parasympathetic nervous systems. The sympathetic nervous system is activated in emergency situations, keeping us alert and preparing us for action by raising our heart rate, increasing blood pressure, and accelerating breathing. In contrast, the parasympathetic nervous system dominates during rest and relaxation.
Studies show that sympathetic activity—such as an increase in heart rate and skin conductance—increases before crying. However, the key finding is that after crying, the balance between sympathetic and parasympathetic activity returns to baseline levels. This suggests that crying serves as a mechanism through which the parasympathetic nervous system suppresses sympathetic activity, helping to restore physiological equilibrium
A Surge of Relief
The brain region responsible for emotional expressions such as crying is located in the brainstem and is called the periaqueductal gray (PAG). Cells in the PAG receive input from the limbic system, our emotional processing center, and then execute an adequate motor program to express emotions, such as laughter or joyful crying. Each component of the process of crying—whether it be vocal sounds, muscle contractions, breathing spasms, or tear production—may contribute to emotional relief in different ways. To understand how the body regains balance, let’s focus on. tears.
When we cry out of happiness, tears are produced by the lacrimal glands, located near the eye sockets. These glands are controlled by nerve endings that either stimulate or inhibit their activity. The nerves regulating tear production belong to both the sympathetic and parasympathetic nervous systems. However, it is specifically the parasympathetic system, associated with relaxation, that stimulates tear production, whereas the sympathetic system suppresses it. In other words, tear production is a parasympathetic response that counteracts the heightened arousal previously induced by sympathetic activity.
participants who shed tears reported a greater sense of mental clarity compared to those who did not cry
Is there something in the tears themselves that brings relief? Among other effects, parasympathetic activity triggers the release of acetylcholine in the lacrimal gland, which facilitates the secretion of various tear components. The composition of emotionally induced tears differs from that of basal tears, which are continuously secreted to protect the eyes. Emotional tears contain electrolytes and various proteins, including hormones and other substances that influence mood. This suggests that, at a physiological level, tears may help release certain chemicals as part of an emotional discharge.
One key substance found in high concentrations in tears is cortisol, a hormone associated with stress. This led researchers to hypothesize that crying removes excess cortisol from the body. To test this, a study had women watch an emotionally moving film, designed to bring them to tears. Cortisol levels in their blood were measured before and after the screening. The results showed that women who cried during the film had lower cortisol levels afterward compared to those who did not cry, suggesting that crying may help reduce stress and restore physiological balance.
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A man crying in front of a computer screen
(Illustrative photo: Khosro, Shutterstock)
Additional hypotheses propose that crying involves other factors that positively impact mood. One such factor is oxytocin, commonly known as the "love hormone", which is generally associated with relaxation and reduced cortisol levels. While most research focuses on oxytocin’s role in responding to another person’s crying, particularly in parental care—only a few studies have examined its direct connection to self-crying. However, oxytocin is known to play a role in parasympathetic activity, and a recent study in dogs suggested that oxytocin enhances tear production. Additionally, studies indicate that both crying and laughter trigger the release of endorphins, natural chemicals in the brain that promote a sense of euphoria.
What’s in Tears?
It turns out that the substances found in tears may not only affect us but also influence those around us. In a study led by Prof. Noam Sobel from the Weizmann Institute of Science, researchers collected tears produced by women who cried out of sadness and analyzed both their composition and their effects on men. They discovered that tears triggered by sadness reduced sexual desire and testosterone levels in men, suggesting that tears of sadness may have a distinct chemical composition from tears of joy. Indeed, a recent study found that basal tears, tears of sadness, and tears of joy are distinct in their chemical composition. This variation may play a role in how tears function as a form of nonverbal communication.
The findings regarding the chemical composition of tears align with psychological research indicating that crying also functions as a social signal—helping to elicit support from others, foster empathy, and strengthen interpersonal bonds. Additional studies reinforce this idea, showing that people are more likely to cry in the presence of others than when they are alone.
A small study that measured brain activity in humans during the buildup and release of tears, shed light on the synchronization between the central nervous system and the autonomic nervous system. Researchers in Japan used near-infrared spectroscopy—a technique that measures changes in blood oxygen levels, an indirect marker of brain activity since active neurons consume more oxygen.
In the study, eight participants watched an emotionally moving film designed to bring them to tears, while researchers monitored oxygen levels in their brains. Before crying began, activity gradually increased in the medial prefrontal cortex (mPFC), a region involved in emotional regulation. At the same time, an increase in heart rate was observed, reflecting heightened emotional intensity and activity of the sympathetic nervous system.
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At the moment crying started, there was a sharp surge in medial prefrontal cortex activity, which researchers interpreted as the transition from sympathetic to parasympathetic dominance. After crying, participants who shed tears reported a greater sense of mental clarity compared to those who did not cry—further supporting the idea that crying activates the parasympathetic nervous system, helping to restore emotional balance.
Ultimately, tears of joy are the body's way of coping with overwhelming emotional waves and regulating them in a manner that promotes mental well-being. So the next time you feel tears welling up, let them flow—your body knows what it’s doing.