Serotonin is a neurotransmitter that regulates mood, sleep, appetite, and cognitive functions. Though primarily found in the intestines, its presence in the brain affects emotional well-being and mental health. Abnormal serotonin levels are linked to depression and anxiety.
Key Takeaways
- Serotonin is a neurotransmitter (chemical messenger) produced within the central nervous system (CNS) that contributes to feelings of happiness.
- Serotonin’s role as a neurotransmitter in the brain is important for functions, such as playing a in mood, especially in relation to mood disorders such as depression and anxiety.
- Too little serotonin has shown associations with depressed feelings, sadness, and fatigue.
- Too much serotonin, however, could result in serotonin syndrome, which could lead to symptoms of restlessness, hallucinations, and confusion.
Functions
Behavior
Serotonin is projected from the brain stem and reaches most regions of the brain, giving it a wide array of effects on many aspects of behavior:
- Controls attention, perception, and memory
- Regulates anger and aggression
- Influences reward processing and motivation
- Affects motor skills and coordination
- Manages appetite and eating behaviors
- Modulates impulsivity and decision-making
Did you know? It is difficult to identify a human behavior that is not regulated by serotonin in some way.
Mood
Serotonin is one of the key neurotransmitters involved in modulating mood, since it:
- Acts as a natural mood stabilizer
- Promotes feelings of happiness and emotional stability
- Helps regulate anxiety levels
- Works with other neurotransmitters (like dopamine) to balance emotions
- Contributes to self-esteem and emotional well-being
- Influences frustration tolerance and irritability levels
Sleep
Serotonin helps regulate sleep by stimulating parts of the brain that control sleep and wakefulness:
- Controls when we fall asleep and wake up
- Regulates sleep patterns through specific brain receptors
- Serves as a precursor to melat onin production
- Different serotonin receptors determine sleep vs. wakefulness states
- Influences sleep quality and duration
Physical Health
Outside of brain functions, serotonin also plays a big role in physical health:
- Maintains digestive function
- Promotes healthy bone density
- Assists in blood clotting and wound healing
- Controls cardiovascular function
- Regulates bladder control and bowel movements
- Influences sexual function
- Helps maintain body temperature
- Affects muscle contraction and relaxation
Did you know: Most of the body's serotonin is found in the gastrointestinal tract rather than the brain.
How Does Serotonin Work?
The scientific name for serotonin is 5-hydroxytryptamine (5-HT), a monoamine group neurotransmitter that contains amino acids.
The monoamine group of neurotransmitters plays a role in many functions, such as decision-making, emotions, happiness, rewards, and has associations with mental health conditions as a result.
Within the brain, serotonin mostly originates in the brain stem within a cluster of nuclei called the Raphe nuclei.
Serotonergic fibers are then synthesized from the Raphe nuclei and projected to the nucleus accumbens, part of the basal forebrain that is known as the circuit area for rewards.
Here, it is then projected throughout the brain, including the lobes of the brain, hippocampus, cerebellum, and spinal cord.
During neurotransmission, serotonin is released into the synaptic cleft from the terminals of the presynaptic neuron.
When it reaches this gap, the serotonin will either be taken up by serotonin receptors on the postsynaptic neuron and continue down the next neuron via electrical impulses, or the serotonin may get degraded by an enzyme called monoamine oxidase, or it will be taken back up into the presynaptic neuron by the serotonin transporter (SERT).
Serotonin can act as both excitatory and inhibitory, depending on the type of receptors it binds to and the location within the brain. Its effect is context-dependent.
In some brain regions or circuits, serotonin can increase neuronal activity (excitatory); in others, it can decrease activity (inhibitory).
Low Serotonin
In regard to serotonin within the brain, there are many symptoms that can be associated with low levels of this neurotransmitter:
- Down in mood or feeling depressed
- Aggression
- Feelings of anxiety
- Irritability and frustration
- Low self-esteem
- Problems with memory
- Poor appetite
- Issues with sleeping and insomnia in worse cases
- Impulsivity
Low levels of serotonin have been associated with some mental health conditions, such as mood disorders, anxiety disorders, and schizophrenia.
Low levels of serotonin could be due to not producing enough of this neurotransmitter. An amino acid called tryptophan is essential for the production of serotonin.
This amino acid is only obtained from food, so if there is a deficiency of this, less serotonin will be made as a result. Similarly, vitamin B6 and D deficiencies have been linked to lower levels of serotonin.
Another cause of low serotonin levels can result from not having enough serotonin receptors in the brain or the receptors not functioning properly.
When serotonin leaves the presynaptic neuron, it could be broken down in the synaptic cleft too quickly or reabsorbed into the presynaptic neuron too soon, stopping it from reaching the next neurons during neurotransmission.
Increasing Serotonin Levels
Increasing serotonin levels can enhance mood, alleviate depression, and regulate sleep and appetite. Proper serotonin balance is essential for emotional and mental well-being.
While medications are often prescribed to treat symptoms associated with low serotonin, there are also natural ways to boost serotonin levels:
- Exercise: Regular physical activity can increase serotonin production and release. Aerobic exercise, such as running, cycling, or swimming, has been shown to have mood-boosting effects.
- Sunlight exposure: Vitamin D, which is produced when the skin is exposed to sunlight, is important for serotonin synthesis. Spending time outdoors or using light therapy can help boost serotonin levels.
- Stress reduction: Chronic stress can deplete serotonin levels. Engaging in stress-reducing activities like meditation, yoga, or deep breathing exercises can help maintain healthy serotonin levels.
- Sleep: Adequate, quality sleep is crucial for serotonin regulation. Aim for 7-9 hours of sleep per night and maintain a consistent sleep schedule.
Medications
Selective Serotonin Re-uptake Inhibitors (SSRIs): The most prescribed antidepressants, SSRIs work by blocking the re-uptake of serotonin, making more available in the brain. Examples include Citalopram (Celexa), Fluoxetine (Prozac), and Sertraline (Zoloft).
Tricyclic antidepressants (TCAs) and Monoamine oxidase inhibitors (MAOIs): Older classes of antidepressants that also increase serotonin levels, but with more side effects compared to SSRIs.
While medications can be effective for treating serotonin imbalances, it’s important to work with a healthcare provider to find the right treatment plan.
Incorporating natural methods to boost serotonin, alongside medical treatment when necessary, can help promote overall emotional well-being.
Too Much Serotonin
Although serotonin is beneficial in maintaining a good mood and providing people with happy feelings, too much serotonin can be detrimental.
A surplus of serotonin in the brain can be a result of the medications that are being taken to increase low serotonin levels.
Too much serotonin in the brain can result in a condition called serotonin syndrome.
This syndrome can arise after starting to take a new medication, or when increasing the dosage of an existing medication.
Some of the milder symptoms associated with serotonin syndrome are as follows:
- Confusion
- Dilated pupils
- Restlessness
- Rapid heart rate
- High blood pressure
- Headaches
- Shivering and goose bumps
Mild cases of serotonin syndrome may go away within a day of stopping the medications causing the symptoms, although if not treated it could result in worsened symptoms such as seizures, irregular heartbeat, unconsciousness, or even death in the worse cases.
Therefore, if someone is considering taking medication for curing symptoms of low serotonin or associated mental health conditions, they would be advised to start with a small dosage before potentially increasing this.
References
Berger, M., Gray, J. A., & Roth, B. L. (2009). The expanded biology of serotonin. Annual review of medicine, 60, 355-366.
Lane, R., Baldwin, D., & Preskorn, S. (1995). The SSRIs: advantages, disadvantages and differences. Journal of psychopharmacology, 9(2_suppl), 163-178.
Mayo Clinic. (2019, October 8). Tricyclic antidepressants and tetracyclic antidepressants. https://www.mayoclinic.org/diseases-conditions/depression/in-depth/antidepressants/art-20046983
