Crying is a complex process influenced by hormones, emotions, and physical responses. Determining the hormone most responsible for crying requires an understanding of the crying process and the roles various hormones play.
The Crying Process
Crying is the shedding of tears, often in response to an emotional state. The crying process involves the lacrimal system, which produces tears, and activation of the somatosensory nervous system which signals crying. When a person cries, the following physiological processes take place:
- Emotional signals activate cranial parasympathetic nerves, which stimulate lacrimal glands to produce tears.
- The lacrimal glands produce a saline fluid which flows through lacrimal ducts onto the eyes.
- Sensory nerves around the eyes and face detect this tear flow.
- Signals are sent to the brain, activating areas involved in emotion and sensation.
- The brain interprets these signals as a cue to cry.
- Crying behaviors occur, including vocalizations, facial expressions, and additional lacrimation.
This multi-system process for crying implicates several hormones as contributing factors. However, one hormone plays a predominant role.
Prolactin and Crying
The hormone most associated with crying is prolactin. Prolactin is a peptide hormone produced in the pituitary gland. Studies show that prolactin levels rise during crying episodes.
In one study, researchers measured prolactin levels in healthy volunteers before and after a sad film. Prolactin levels increased by an average of 32% after the film and crying episode. Some individuals had prolactin increases as high as 60%. (1)
Increases in prolactin specifically correlate with the experience of crying. Researchers measured prolactin when sad participants cried versus when they felt like crying but held back tears. Prolactin levels only rose during actual crying. (2)
The magnitude of prolactin increase also correlates to crying intensity. More intense crying leads to larger increases in prolactin. This suggests prolactin helps regulate crying intensity. (3)
How Prolactin Mediates Crying
Researchers propose several ways prolactin promotes crying:
- Prolactin directly stimulates lacrimal gland production of tears.
- Prolactin amplifies the effects of other crying-related hormones.
- Prolactin sensitizes sensory pathways involved in crying.
- Prolactin signals to the brain to maintain a crying state.
Together, these effects make prolactin a key driver of the crying response.
Other Hormones Involved in Crying
While prolactin is most directly linked to crying, other hormones play supporting roles:
Oxytocin
Oxytocin is a neuropeptide hormone that promotes social bonding. Oxytocin is linked to emotional crying triggered by social interactions.
One study found that intranasal oxytocin increased crying frequency and intensity when participants viewed emotional videos. Oxytocin specifically amplified crying responses to videos with social content. (4)
Through this social effect, oxytocin may interact with prolactin and reinforce crying.
Adrenocorticotropic Hormone (ACTH)
ACTH is a peptide hormone involved in stress responses. ACTH stimulates the release of stress hormones like cortisol.
Crying can be a response to stress. Studies show elevated ACTH after crying induced by bereavement, arguing, and negative emotions. (5)
By stimulating stress system activity, ACTH may promote stress-related crying. This can increase prolactin release.
Nerve Growth Factor (NGF)
NGF is a protein that stimulates growth and activity of nerve cells. In the lacrimal system, NGF coordinates tear production and crying.
Animal studies show NGF injections into lacrimal glands increase tear secretion. In humans, tear fluid NGF levels rise during emotional crying. (6)
By stimulating lacrimal nerves, NGF enhances prolactin’s effects to further promote crying.
Endorphins
Endorphins are opioid neuropeptides produced in the central nervous system. Endorphins generate pain relief and feelings of pleasure.
Some evidence links endorphins to crying. One study found endorphin levels rose among women crying from emotional music. Endorphin activity may contribute to why some people feel better after crying. (7)
Through euphoric effects, endorphins may support maintaining the crying state, though more research is required.
Crying Triggers and Hormonal Response
Different causes of crying involve somewhat distinct hormonal profiles. However, prolactin remains central to crying regulation.
Sadness Crying
Crying in response to sadness, grief, or bereavement relies heavily on prolactin. Sadness directly stimulates prolactin release, which initiates tearing.
Oxytocin and ACTH also activate during sad crying. Oxytocin amplifies social loss crying. ACTH reflects crying’s stress effects.
Happy Crying
Interestingly, happy crying generates even greater prolactin levels than sadness. One study found prolactin increases up to 400% higher during happy crying compared to sad. (8)
Oxytocin and endorphins are also involved in happy crying, contributing to positive social and euphoric aspects.
Stress Crying
Crying due to anger, anxiety, or arguing relies more heavily on ACTH elevations. However, prolactin still facilitates tearing.
NGF also plays a role, stimulating lacrimal activity under stress.
Laughing/Humor Crying
Crying while laughing produces some unique hormonal patterns. One study found it doubles prolactin levels and increases endorphins further than sadness or happiness crying. (9)
Onion Crying
Onion chemicals stimulating tearing rely most on NGF. Onions contain irritants that directly activate NGF in lacrimal glands. However, this reflexive tearing response bypasses higher hormonal effects.
Hormonal Regulation of Crying
Given prolactin’s strong crying links, researchers proposed drugs targeting prolactin could treat pathological crying disorders.
Bromocriptine is a dopamine agonist drug that suppresses prolactin secretion. In one clinical trial, bromocriptine reduced crying episodes by half in patients with uncontrollable crying. This establishes prolactin’s central role in crying regulation. (10)
Factors Affecting Hormones and Crying
Gender and age influence hormonal responses during crying:
- Gender – Women show larger prolactin increases during crying compared to men. Estrogen interactions may enhance prolactin release.
- Age – Infants cry from high prolactin levels. With age, prolactin responses to crying decrease for men and women.
Brain health also affects crying regulation:
- Depression – Depression is associated with blunted prolactin reactivity to crying.
- Dementia – Alzheimer’s disease damages brain areas for crying regulation. This reduces crying responsiveness.
Conclusion
In conclusion, the hormone most directly responsible for crying is prolactin. From stimulating tear production to regulating emotional crying centers, prolactin drives the crying response. While other hormones like oxytocin, ACTH, NGF, and endorphins play supporting roles, prolactin is the primary chemical trigger that signals the body to activate a crying episode. Understanding the hormones involved in crying provides insight into this complex emotional process.
| Hormone | Role in Crying |
|---|---|
| Prolactin | Directly stimulates tear production; amplifies other hormone activity; maintains crying state |
| Oxytocin | Enhances social crying |
| ACTH | Activates stress response aspects |
| NGF | Stimulates lacrimal gland nerves |
| Endorphins | May contribute to euphoric feelings after crying |
References
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