Serotonin is a neurotransmitter that plays a role in behavior, mood, movement, learning, and many other functions. Its technical name is 5-hydroxytryptamine or 5-HT. Like all neurotransmitters, serotonin carries a nerve signal across a synapse.
When serotonin levels are too low, this can weaken nerve signals. One of the most common symptoms of low serotonin is depression, but low serotonin levels can affect almost every system of the body, leading to a wide range of symptoms.
Understanding Serotonin: What Does Serotonin Do?
Researchers have studied serotonin for more than 60 years and uncovered roles for this important neurotransmitter in numerous brain functions. All animals and even plants produce serotonin, suggesting it appeared very early in evolution.
Yet serotonin is difficult to isolate. Moreover, a wide range of neurotransmitters—as well as other factors, such as a person’s overall health, environment, and unique biology—can affect mental and physical health. This has made it difficult for researchers to establish direct correlations between serotonin and various functions.
Researchers have long thought serotonin deficiency can lead to depression. In fact, many popular antidepressants increase brain serotonin levels. Yet some studies throw even this widely accepted theory of serotonin into question. A 2014 study of mice, for example, found that genetically lowering serotonin levels did not lead to depression. Clinicians have long theorized that serotonin levels are genetically low in some people with depression, so this study undermines that theory.
Numerous ailments can cause symptoms of serotonin deficiency, so it’s important to see a health care provider to get an accurate diagnosis and appropriate treatment.
This mixed research means it is impossible to diagnose serotonin deficiency based on symptoms alone. People with normal serotonin levels may experience symptoms consistent with serotonin deficiency, while some people with low serotonin may have no symptoms at all. Numerous ailments can cause symptoms of serotonin deficiency, so it’s important to see a health care provider to get an accurate diagnosis and appropriate treatment.
What Causes Serotonin Deficiency?
Most cases of serotonin deficiency are idiopathic, meaning doctors are unable to find a specific cause. Some inherited genetic disorders may affect the body’s ability to make or metabolize serotonin. Lifestyle and other factors that may also play a role include:
- Hormonal shifts, such as due to beginning or stopping hormone replacement therapy, menopause, pregnancy, or advancing age
- Lack of sunlight
- Poor nutrition
- Certain drugs and medications, especially when used to excess or over a long period of time
- Chronic stress
10 Serotonin Deficiency Symptoms
Serotonin never acts alone, and it’s part of a complex system. People with serotonin deficiency may also have deficiencies in other neurotransmitters, as well as metabolic or other health problems. Some common signs of serotonin deficiency include:
Research increasingly points to a complex relationship between depression and serotonin. We don’t fully understand how serotonin deficiency can cause depression, but most studies argue that it is a factor. Depression related to life events, especially chronic stress and trauma, may also deplete serotonin levels. So serotonin deficiency can be both a cause and a result of depression.
2. Changes in sleep
Serotonin helps regulate the body’s internal clock, including the ability to feel sleepy, remain asleep, enter rapid eye movement (REM) sleep, and wake in the morning. People with chronic insomnia, unusual sleep patterns, chronic fatigue, or consistently vivid dreams may have serotonin deficiency.
3. Chronic pain
Serotonin affects the way the muscles behave, so low serotonin may cause chronic pain. Low serotonin is strongly correlated with fibromyalgia, a type of widespread chronic pain. People with fibromyalgia may even get relief from antidepressants that raise serotonin levels.
4. Memory or learning issues
Some studies have linked serotonin to memory and learning, so sudden difficulties with memory or learning could signal a serotonin issue. Additionally, other symptoms of serotonin deficiency, such as sleep deprivation and depression, can make it difficult to concentrate and learn.
Anxiety, including obsessive-compulsive forms of anxiety, may indicate a person has low serotonin. Anxiety that comes on suddenly and appears unrelated to something else, such as a recent trauma or stressor, is often due to a serotonin issue. Chronic stress and anxiety may also deplete serotonin.
Many studies have found low serotonin levels in people with schizophrenia. Unusual beliefs or behaviors, auditory or visual hallucinations, and sudden changes in mood or personality may be a sign of low serotonin.
7. Problems with the body’s internal clock
Serotonin helps regulate the body’s circadian rhythm, which is its internal clock. Though it’s common for people to have difficulties getting up in the morning or occasionally forget meals, dysregulation in the internal clock can cause serious sleep, appetite, and other issues. A person who never sleeps according to a regular schedule, who has difficulty maintaining a consistent pattern of hunger and eating, or who feels chronically tired or hyper could have a problem with their circadian rhythm. This may be due to low serotonin.
8. Appetite issues
A number of studies have found that people with low serotonin may have appetite issues or eating disorders. This may include overeating, not eating enough, or alternating between the two. Additionally, some people with depression also experience problems with appetite.
It’s possible for a person whose blood serotonin levels appear normal to have very little usable serotonin.
Low serotonin can cause symptoms of attention deficit/attention-deficit hyperactivity (ADD/ADHD). A person may have trouble concentrating, constantly fidget, be chronically bored, or be unable to sit still. Children may appear to have boundless energy, behave aggressively, or frequently get into trouble at school.
A handful of new studies suggest that low brain serotonin is linked to dementia and may even be an early warning sign of this group of diseases. It’s unclear if the low serotonin causes dementia or is a symptom. Because serotonin can affect memory, concentration, and other cognitive functions, however, it’s possible that drops in serotonin increase the risk of dementia as a person ages.
Serotonin Deficiency Diagnosis and Treatment
A serotonin blood test can measure levels of serotonin in the blood. However, doctors usually only use this test to check for serotonin-producing tumors. Doctors don’t usually perform blood tests to assess serotonin levels because factors other than blood serotonin—such as metabolism, the behavior of serotonin receptors, and hormones—can affect the body’s ability to process and use serotonin. It’s possible for a person whose blood serotonin levels appear normal to have very little usable serotonin.
Instead of testing serotonin levels, doctors typically treat a person’s symptoms. Depending on the symptoms you have, your provider may recommend tests to rule out other causes, such as hormone imbalances or a physical injury. Then they may recommend a medication that raises serotonin levels, such as an antidepressant. In some cases, providers may also recommend lifestyle changes such as exercise.
Serotonin deficiency is a complex issue. Lifestyle and psychological factors often play a central role. Moreover, symptoms of serotonin deficiency can affect a person’s relationship and quality of life. Therapy can help in numerous ways. For people with depression related to low serotonin, a therapist can offer lifestyle management tips, a sympathetic ear, and help with relationship issues.
Therapy can also help people with low serotonin become better advocates for themselves. For example, a person with fibromyalgia or chronic pain may struggle to talk to loved ones about their symptoms or feel reluctant to request accommodations at work. Therapy can help them explore their options, adopt healthy self-care strategies, and advocate for their needs.
For help finding a therapist who can support you as you deal with low serotonin, click here.
- Al-Nimer, M. M., Mohammad, T. M., & Alsakeni, R. (2018). Serum levels of serotonin as a biomarker of newly diagnosed fibromyalgia in women: Its relation to the platelet indices. Journal of Research in Medical Sciences, 23(1), 71. doi: 10.4103/jrms.JRMS_859_17
- Angoa-Pérez, M., Kane, M. J., Briggs, D. I., Herrera-Mundo, N., Sykes, C. E., Francescutti, D. M., & Kuhn, D. M. (2014). Mice genetically depleted of brain serotonin do dot display a depression-like behavioral phenotype. ACS Chemical Neuroscience, 5(10), 908-919. doi: 10.1021/cn500096g
- Brain scan study adds to evidence that lower brain serotonin levels are linked to dementia. (2017, August 14). Retrieved from https://www.hopkinsmedicine.org/news/media/releases/brain_scan_study_adds_to_evidence_that_lower_brain_serotonin_levels_are_linked_to_dementia_
- Frazer, A., & Hensler, J. G. (1999). Serotonin. In G. J. Siegel (Author), Basic neurochemistry: Molecular, cellular and medical aspects (6th ed.). Amsterdam: Elsevier Academic Press.
- Whitney, M. S., Shemery, A. M., Yaw, A. M., Donovan, L. J., Glass, J. D., & Deneris, E. S. (2016). Adult brain serotonin deficiency causes hyperactivity, circadian disruption, and elimination of siestas. Journal of Neuroscience, 36(38), 9828-9842. doi: 10.1523/JNEUROSCI.1469-16.2016
© Copyright 2019 GoodTherapy.org. All rights reserved.
The preceding article was solely written by the author named above. Any views and opinions expressed are not necessarily shared by GoodTherapy.org. Questions or concerns about the preceding article can be directed to the author or posted as a comment below.