Normal and Abnormal Hormonal Function

Serotonin, also known as 5-hydroxytryptamine (5-HT), is a neurotransmitter (chemical messenger) that helps regulate various functions in the brain and body. Researchers have linked too-high and too-low levels of serotonin to a range of symptoms and conditions.

Medications called selective serotonin reuptake inhibitors (SSRIs) can increase serotonin levels and are the most common type of medication used to treat depression (often caused by too-low serotonin). Still, too much can lead to serotonin syndrome, a potentially life-threatening reaction.

Normal Serotonin Function and Production

An average serotonin level is between 50 and 200 nanograms per milliliter (ng/mL). The body requires normal serotonin levels for optimal physical healing, sleep, and mood. Your gut produces about 95% of serotonin, while the brain makes 5%. However, the gut and brain communicate to determine how much serotonin to produce overall.

When serotonin levels are too low or too high, they can impact various aspects of your health.

Effects of Too Little Serotonin 

It is unclear whether low serotonin causes depression or is a side effect of having depression. Regardless of the relationship, researchers have linked low levels of serotonin to adverse impacts on mental, physical, and social health.

Mental Health

Low serotonin levels are linked to depression and other mental health disorders. However, even people without mental health conditions can have low serotonin levels.

Your serotonin receptors can change when you experience stressful life events and other circumstances that increase levels of the stress hormone cortisol, indicating a link between low serotonin and high stress. Because the relationship between serotonin and depression is not well understood, the side effects of and risk factors for low serotonin are similar and include the following:

It is unclear if mental health concerns such as anxiety and depression are risk factors or symptoms of low serotonin or if there is a different relationship. For example, stress and other mental health concerns may lower serotonin levels, and low serotonin levels may increase symptoms of stress and mental health concerns.

Physical Health

In addition to their effect on mental health, low serotonin levels are also related to physical health. Researchers have found a connection between low serotonin levels and inadequate exercise or physical movement. Other physical health risk factors include:

This can be both a risk factor and an effect, as exercise can increase serotonin levels. Low serotonin levels can lead to physical side effects such as:

Social Health

Beyond physical and mental health, serotonin levels are related to social health, including your friendships, professional and workplace interactions, and family dynamics, which can impact many areas of life. Social risk factors for low serotonin include:

• Feeling lonely
• Lack of close relationships with family or friends
• Negative interactions with others

Low serotonin levels can have an impact on your social health. For example, low serotonin levels may affect how parents interact and care for their babies, influencing a child’s development and well-being. Additional social impacts include:

• Decreased ability to care for babies and children
• Feeling negatively about others
• Negative interactions with others
• Not wanting to be in social environments
• Withdrawal in social situations

Effects of Too Much Serotonin 

High serotonin, called serotonin syndrome, is caused by taking too much medication that increases serotonin levels. This may include a dose that is too high, combining two or more medications that increase serotonin levels, or recreational drug use. The rates of serotonin syndrome have gone up as antidepressant use has increased.

Mental Health

Having a mental health diagnosis such as depression and taking antidepressant medications is a risk factor for high serotonin levels. This is because medications that increase serotonin levels, such as SSRIs, cause serotonin syndrome. Additional mental health risk factors for high serotonin include:

• Taking an excessive dosage of medications that increase serotonin levels
• Combining medications that increase serotonin levels
• Overdosing on recreational drugs

Mental signs that your serotonin levels are too high include:

Physical Health

Serotonin syndrome symptoms can range from mild to severe. For example, mild symptoms may include muscle twitching and sweating, while severe symptoms may include seizures and loss of consciousness.

Regardless of the severity of the symptoms, it is important to immediately stop taking the medications under a healthcare provider’s guidance and seek emergency medical care. Physical symptoms of high serotonin include:

Social Health

In addition to antidepressant medications and other medications that increase serotonin levels, recreational drug use can lead to serotonin syndrome. For example, ecstasy, also known as 3,4-methylenedioxymethamphetamine or MDMA, can increase serotonin levels. Social interactions with people who use recreational drugs can increase the risk of trying such substances, which increases the risk of serotonin syndrome.

How to Manage Serotonin Levels

You can manage your serotonin levels medicinally and naturally. Certain medications, such as SSRIs, increase serotonin levels, and stopping them under the guidance of a healthcare provider will decrease them. Additionally, you can manage serotonin levels naturally with lifestyle changes. For example, exercise can increase serotonin levels without increasing the risk of serotonin syndrome.

Ways to Increase Serotonin

SSRIs are medications that are often used to increase serotonin levels and treat depression. One possible drawback of this option is that they can increase serotonin levels too much, which can lead to serotonin syndrome. Serotonin levels can also be increased naturally without increasing the risk of serotonin syndrome.

Ways to increase serotonin levels without medications include:

• Decreasing stress levels
• Eating certain foods, including leafy greens, nuts, and salmon
• Exercising regularly
• Spending time in the sun

Ways to Decrease Serotonin 

The first course of action to decrease serotonin levels that have become too high is to stop taking any medications that may increase these levels. It is also essential to seek immediate, emergency medical care when you are taking SSRIs and suspect that you have serotonin syndrome, as this condition can be fatal. Healthcare providers treat this condition with medications and supportive care such as fluids.