By Valerie Battaglia

Serotonin is a hormone associated with mood regulation and well-being, but its functions go far beyond that. Countless research over the last few decades has linked serotonin to regulating stress, as well as sleep, digestion and body temperature.

The hormone has also been critical to furthering the understanding of various neurological, behavioral and emotional conditions, such as depression and migraines.

Serotonin and the Brain

On a neurological level, serotonin helps brain cells communicate with one another, according to Hormone Health Network.

Serotonin naturally stabilizes emotions, attention span and happiness. Low levels of serotonin are associated with emotional or behavioral disorders, such as anxiety, depression and obsessive-compulsive disorder.

However, it’s important not to confuse serotonin with the happiness hormone, “dopamine,” a chemical released by neurons that plays a vital role in learning and motivation, states a 2018 Nature Neuroscience review.

Both serotonin and dopamine contribute to maintaining happiness, according to a 2014 Iranian Journal of Public Health review.

Higher levels of dopamine are associated with an uplifted mood that has an impact on cognition.

Dopamine also signals to the brain how rewarding an activity may be, as seen in Nature Neuroscience’s review. When an activity doesn’t stimulate the release of dopamine, there’s less motivation to devote attention and energy to the task.

Alternatively, serotonin is associated with the stability of happiness, satisfaction and optimism, states the Iranian Journal of Public Health’s review.

In other words, dopamine motivates and makes you happy, while serotonin maintains happiness and satisfaction. Similar, but not quite the same.
Serotonin and Stress

A 2017 review published in the Journal of Psychopharmacology found serotonin enhances the body’s response to stress by acting on neural pathways responsible for coping, stress tolerance and neuroplasticity.

Neuroplasticity refers to the brain’s ability to adapt and change, according to Brainline, a national information center for brain injury and PTSD. Serotonin makes it easier for the brain to restructure physiologically, which would be useful in prolonged periods of stress.

However, chronic stress can also alter serotonin receptors and lead to a decrease in the hormone, states research published in The Journal of Neuroscience in 2017.

Serotonin and Depression

As stated in a 2015 World Psychiatry review, researchers have suspected serotonin is at the root of depression for over half a century.

While recent research is beginning to uncover the cause of depression may also stem from other complex factors, serotonin still relates to the condition.

The World Psychiatry review says serotonin is related to depression recovery. Their findings suggest that low serotonin can trigger another depressive episode in individuals who have been depressed or ill in the past, but the same can’t always be said for those who have never been depressed or ill before.

“Balancing serotonin levels is critical to physical and mental wellness.”

– Valerie Battaglia

This aligns with serotonin’s role in mood regulation and maintaining happiness; if you have suffered a depressive episode before, a decrease in serotonin would inhibit your ability to maintain a positive mood after recovering.

Serotonin deficits are also evident in cases of major depressive disorder, alcohol use disorder and suicide, found research published in Translational Psychiatry in 2018. Recurring depressive episodes would be common among those diagnosed with major depressive disorder and alcohol use disorder, as well as those who have died by suicide, which supports the evidence in World Psychiatry’s review.

Serotonin and Migraines

According to a 2017 The Journal of Headache and Pain review, migraines are caused by ion channel dysfunction, which disrupts electrical activity in the brain. Migraine sufferers also display varying levels of neurotransmitter dysfunctions, which impact the brain’s ability to create, release and filter out serotonin.

This could explain the cause of multiple symptoms associated with migraines, such as fatigue, nausea, loss of appetite and mood disruptions.

Triptans are a class of drugs that mimic serotonin and are commonly used to treat migraines, reports the U.S. National Library of Medicine.

A study published in Neuroimage Clinical last year disputed evidence in prior studies that suggested migraines were a symptom of overall low serotonin levels. By contrast, their participants who had chronic migraine attacks showed higher levels of serotonin than average in between migraine episodes. The migraine group also displayed lower levels of receptors binding to serotonin.

Rather than a serotonin deficit, those who suffer from chronic migraines may have excess serotonin that isn’t binding properly to their neurotransmitter receptors during migraine-free periods.

Additional research published in the Annals of Neuroscience says a drop in serotonin is observed in those who have migraines during an attack. In their study, they observed migraines caused by a drop of serotonin from a decrease in estrogen during menstruation or from taking birth control.

Other factors, such as diet, sleep and stress, can affect serotonin levels, which explains why some of the most common migraine triggers relate to these three factors.

Serotonin and Sleep

Serotonin is the precursor to melatonin, a hormone that affects reproduction and sleep-wake cycles, reports Colorado State University.

According to the National Sleep Foundation, melatonin is produced by the pineal gland at night. Research shows that taking melatonin on it’s own won’t make you fall asleep, but it can help reset the body’s biological clock in cases of jet lag or shift-work.

Together, serotonin and melatonin play a vital role in maintaining circadian rhythm. Serotonin is converted into melatonin.

Serotonin and Digestion

Most serotonin in the body is created, stored and released by cells within the digestive tract. This contributes to how the gut communicates with the central nervous system.

Serotonin has long since been recognized as an important molecule for signaling movement in the digestive tract, according to research published in Nature Reviews Gastroenterology & Hepatology in 2013.

Serotonin also signals to the brain whether the body feels full and communicates discomfort related to digestion, such as nausea or abdominal pain.

Serotonin and Body Temperature

Thermoregulation is another function of serotonin, but the connection remains quite complicated.

So far, it’s known that chronic stress affects serotonin, disrupting body temperature regulation, based on evidence from 2016 in the peer-reviewed journal, Stress.

In 2012, Pharmacological Reviews’ research observed a serotonin-induced decrease in body temperature that correlated with lowered blood pressure over a long-term period.

Rats with a serotonin deficiency were unable to regulate their body temperature or breathing when exposed to cold temperatures, found a 2016 study in the Journal of Applied Psychology.

2014 research in The Journal of Steroid Biochemistry and Molecular Biology says serotonin can be effective in treating hot-flashes during menopause, which are caused by a slight elevation in core body temperature.

However, excess serotonin – like in serotonin syndrome – can result in fever, according to The Ochsner Journal.

MDMA, commonly known as ecstasy, is an illicit drug commonly associated with fever and dehydration, the National Institute on Drug Abuse says online.

One of the hormones released during MDMA use is serotonin, potentially inducing serotonin syndrome in high dosages, which explains why fever is a concern among users.

While serotonin is critical to regulating a wide variety of bodily and behavioral functions, too much of a good thing can be a bad thing. Serotonin deficits may cause physiological and psychological dysfunction, but excess serotonin can be deadly, says The Ochsner Journal.

Triptans, SSRIs, and illicit drugs aren’t the only way to increase your serotonin levels. Tryptophan is an amino acid found in food that helps the body create serotonin, according to The National Sleep Foundation.

Foods high in protein and carbohydrates – such as turkey, chicken, eggs, bananas, soybeans and nuts – are brimming with tryptophan which can help your body naturally create more serotonin.

Serotonin keeps the body balanced, but balancing serotonin levels is critical to physical health and mental wellness. Naturally increasing serotonin through diet provides a safer alternative to keeping the brain and body in check.

Contact Valerie Battaglia at communitarian@mail.dccc.edu