Serotonin is a neurotransmitter that plays a vital role in regulating many essential bodily functions, including mood, appetite, and sleep. It's known as a "happy chemical" due to its effects on mental health and well-being.
But there's more about serotonin than meets the eye. Let's take a closer look at what this hormone is, how it works in the body, and why it's so important.
Table of contents
- 1 What is serotonin?
- 2 Serotonin function: keeping the mind and body in balance
- 3 Why is serotonin a "happy chemical"?
- 4 Do low levels of serotonin lead to depression? Not so fast
- 5 Serotonin and SSRIs
- 6 Symptoms of low serotonin
- 7 Serotonin and the Gut
- 8 How to Naturally Boost Serotonin
- 9 The rundown on serotonin
What is serotonin?
Serotonin, also known as 5-hydroxytryptamine (5-HT), is a neurotransmitter, which means it acts as a chemical messenger in the brain.
Serotonin is synthesized in the gut and the brain from the amino acid tryptophan. Tryptophan is an essential amino acid -- this means the body can't produce it. In other words, you need to obtain tryptophan from the food you eat.
After your body produces serotonin, it sends it through the bloodstream. Ultimately, the hormone is taken up by nerve cells, it transmits signals between cells.
Serotonin function: keeping the mind and body in balance
One of the primary functions of serotonin is to regulate mood. Serotonin stabilizes and balances emotions, promoting feelings of happiness and well-being. But the importance of serotonin is multifaceted.
Serotonin also plays a role in regulating appetite, sleep, and other bodily processes. For instance, serotonin can play a major role in the cardiovascular system, where it helps regulate blood pressure and clotting.
But how does serotonin actually work in the brain? This is, after all, our biggest concern with this neurotransmitter.
When the brain releases serotonin, the neurotransmitter binds to specific receptors and affects different regions, including the prefrontal cortex, the limbic system, and the hypothalamus. These areas play an essential role in regulating emotion, cognition, and motivation, among other functions.
One way to think about the function of serotonin is as a regulator. The neurotransmitter helps maintain balance in the body, ensuring that different bodily functions work together seamlessly.
Why is serotonin a "happy chemical"?
Serotonin has earned the nickname "happy chemical" due to its role in regulating mood and emotions.
Balanced levels of serotonin help people tend to feel calm, content, and happy. However, when serotonin levels are low, it can lead to feelings of anxiety, depression, and other mood disorders.
Scientists are still working to fully understand how serotonin works in the brain and what factors influence its production and release. However, it's clear that maintaining healthy serotonin levels is essential for maintaining good mental health and overall well-being.
Do low levels of serotonin lead to depression? Not so fast
One of the most well-known connections between serotonin and mental health is its role in conditions such as depression. This connection is pretty famous. In fact, most people will tell you that depression is caused by a serotonin imbalance. But is this actually the case?
Depression is a common mental health condition that affects millions of people worldwide. Persistent feelings of sadness, hopelessness, and low energy are common symptoms of depression.
Scientists first proposed the "serotonin theory of depression" in the 1960s serendipitously. They noticed that some patients suffering from depression who took monoamine oxidase inhibitors improved their symptoms. Later studies on animals showed such drugs potentiate the effects of serotonin at the synapses.
Later research found it hard to confirm these studies. However, some studies showed found a link between low levels of serotonin and an increased risk of depression. In particular, low levels of serotonin in certain regions of the brain, such as the prefrontal cortex, seem linked to depressive symptoms.
The rest is, as they say, history. Today, more than 1 in 10 Americans over the age of 18 use antidepressant medication at least once in the past 30 days. These medications include SSRIs (selective serotonin reuptake inhibitors) such as Prozac to boost serotonin levels. Antidepression medication is now a multi-billion dollar industry.
“The hypothesis that depression was caused by a chemical imbalance in serotonin was a really important step forward in the middle of the 20th century. Since then, there is a huge of amount of research which tells us that the brain’s serotonin systems plays very important roles in how our brains process different emotions," says Dr. Michael Bloomfield, Consultant Psychiatrist and UKRI Principal Clinical Research Fellow, at the University College London.
However, most recently, scientists have abandoned the serotonin theory of depression. The bottom line is that direct evidence linking low levels of serotonin to depression is incredibly thin. Researchers brilliantly confirmed this in a recent study.
In 2022, psychiatrists Professor Joanna Moncrieff and Dr. Mark Horowitz of University College London published a bombshell study. They performed an "umbrella" review of the current scientific literature that delved into the connection between serotonin and depression. They looked at 361 peer-reviewed scientific studies.
The findings sent shockwaves through the psychiatric community at large. The paper concluded that there's “no clear evidence” that low serotonin levels are responsible for depression.
“I had been taught that depression was caused by low serotonin in my psychiatry training and had even taught this to students in my own lectures,” said Horowitz in a press release.
“Being involved in this research was eye-opening and feels like everything I thought I knew has been flipped upside down.”
Some of the key findings of this landmark review include:
- Patients who used antidepressants had lower levels of serotonin in their blood. This suggests that any short-term increase in serotonin produced by some antidepressants could lead to compensatory long-term changes in the brain.
- Levels of serotonin and its byproducts in the blood or brain fluid are indistinguishable between people with depression and those without it.
- There is no difference in serotonin receptors between people with depression and healthy people. In some studies the researchers looked at, people with depression actually had more serotonin activity. This is the exact opposite of what you'd expect with the serotonin theory of depression.
- Two other systematic reviews from 2006 and 2007 analyzed by the researchers found that lowering serotonin did not produce depression in hundreds of healthy volunteers. In other words, you can't seem to induce depression in individuals by simply lowering serotonin levels.
- The serotonin transporter protein is coded by certain genes. There is no difference in the frequency of varieties of this gene between people with depression and healthy controls.
Serotonin and SSRIs
If these findings are valid, it would mean we've been dealing with depression all wrong. In particular, it means we shouldn't use SSRI antidepressants -- which block serotonin reuptake in the brain and cause a number of very nasty side effects -- to treat depression. Indeed, this is exactly what Moncrieff and Horowitz are suggesting.
“Our view is that patients should not be told that depression is caused by low serotonin or by a chemical imbalance, and they should not be led to believe that antidepressants work by targeting these unproven abnormalities,” Moncrieff said.
“We do not understand what antidepressants are doing to the brain exactly and giving people this sort of misinformation prevents them from making an informed decision about whether to take antidepressants or not.”
SSRI drugs fail to improve depression symptoms in about 30% of patients. Side effects include nausea, dizziness, and sexual dysfunction.
But what about the patients who respond to antidepressants? Scientists are reluctant to draw any definite conclusions. However, some drug trials show that antidepressants are barely distinguishable from a placebo (dummy pill) when it comes to treating depression.
Even before this landmark review, many psychiatrists viewed the serotonin theory as outdated. Although we need more research, it is rather clear now that it's not just a single neurotransmitter that causes depression. Instead, depression is shaping up to be much more complex than it looked at first glance in the 1960s.
For instance, negative life events and stress, as well as certain genetic predispositions, are shaping up as more reliable predictors of depressive symptoms.
"Life events have a huge impact on depression," Patricia Fonseca, a psychiatrist at the Max-Planck-Insitut for Psychiatry in Munich, Germany, told DW. "But an important fact is also the influence of genetic factors. By having a special genetic predisposition, distressing life events can trigger the onset of depression."
Symptoms of low serotonin
While depression is a multifactorial condition, science is more definitive about the link between low serotonin and mood changes, sleep problems, and digestive conditions (i.e. irritable bowel syndrome).
Some of the physical symptoms of low serotonin in the brain and gut include:
Serotonin and the Gut
While serotonin is produced in the brain, it's also produced in the gut. In fact, the gut produces up to 90% of the body's serotonin.
This connection between the gut and the brain is known as the gut-brain axis. This is still very much an active and growing research interest. Scientists are still working to fully understand the mechanisms behind this connection. However, what is clear is that the gut and the brain are in constant communication. Furthermore, this connection can influence many different bodily functions.
Some research has suggested that gut bacteria may play a role in regulating serotonin production and release. Additionally, changes in gut health and function and mental health conditions such as depression and anxiety seem to go hand in hand.
Clinicians have been taking note of this. Increasingly, they are recommending a new approach in psychiatry. This approach uses dietary interventions and probiotics to improve mental health. We still need more research to see just how well this can work, but existing evidence suggests that healthy gut may be essential for maintaining good mental health.
How to Naturally Boost Serotonin
While doctors prescribe medication for serotonin imbalance, there are also many natural ways to support healthy serotonin production and release.
Here are some tips for naturally boosting serotonin:
Eat a healthy diet
Eating a balanced diet rich in whole foods is essential for supporting healthy serotonin levels. Foods that are high in tryptophan, the amino acid that serotonin is made from, include:
- Poultry, such as chicken and turkey;
- Fish, such as salmon and tuna;
- Cheese, such as cheddar and Swiss;
- Nuts and seeds, such as pumpkin seeds and peanuts;
- Legumes, such as soybeans and lentils;
- Milk and dairy products;
- Whole grains, such as oats and quinoa.
Considering the gut-brain axis idea, it may be a good idea to include probiotic-rich foods in your diet, such as:
Additionally, foods that are rich in complex carbohydrates, such as whole grains, fruits, and vegetables, can help to boost serotonin levels. This is because carbohydrates increase insulin production, which helps to transport tryptophan into the brain.
Get regular exercise
Regular exercise is another excellent way to naturally boost serotonin levels. Exercise helps to release endorphins, which are another type of "feel-good" chemical in the brain. We already have evidence that exercise can increase serotonin production and release in the brain.
Practice relaxation techniques
Stress and anxiety can negatively impact serotonin levels, so practicing relaxation techniques like meditation, yoga, and deep breathing can help to promote feelings of calm and relaxation. This can, in turn, help to boost serotonin levels.
Spend time in nature
Spending time in nature has been shown to have many mental health benefits, including boosting serotonin levels. Even just a short walk in the woods or spending time in a park can help to promote feelings of well-being and relaxation.
Get enough sleep
Finally, getting enough sleep is essential for maintaining healthy serotonin levels. Sleep helps to regulate many bodily functions, including mood, appetite, and sleep. Getting at least 7-8 hours of sleep each night can help to promote healthy serotonin levels and overall well-being.
There are some supplements that may help boost serotonin levels in the brain, but it's important to note that their effectiveness may vary depending on the individual and the dosage.
Some potentially serotonin-boosting supplements include:
- 5-HTP: 5-HTP is a compound that is naturally produced in the body and is a precursor to serotonin. Taking 5-HTP supplements may increase serotonin levels and has been studied for its potential benefits in treating depression, anxiety, and insomnia.
- Omega-3 fatty acids: Omega-3 fatty acids are essential fats that have been linked to numerous health benefits, including improving mood and reducing inflammation. Studies have suggested that omega-3 fatty acid supplements may help increase serotonin levels in the brain.
- St. John's Wort: St. John's Wort is a herb that has been used for centuries to treat various ailments, including depression. It is believed to work by increasing serotonin levels in the brain. However, it's important to note that St. John's Wort may interact with other medications and cause side effects.
- Saffron: Saffron is a spice that has been traditionally used for its medicinal properties, including improving mood. Some studies have suggested that saffron may increase serotonin levels in the brain and improve symptoms of depression.
- Probiotics: Probiotics are live bacteria that are beneficial for gut health. Emerging research has suggested that probiotics may also have a positive effect on mood and anxiety by increasing serotonin levels.
It's important to note that while these supplements may help increase serotonin levels in some people, they may not work for everyone, and it's essential to speak with a healthcare provider before starting any new supplements.
The rundown on serotonin
In summary, serotonin is a chemical messenger in the body that plays a critical role in regulating mood, appetite, and other bodily functions. Maintaining healthy serotonin levels is essential for good mental health and overall well-being.
While medications like SSRIs can sometimes be effective for boosting serotonin levels, there are also many natural ways to support healthy serotonin production and release, including eating a healthy diet, getting regular exercise, practicing relaxation techniques, spending time in nature, and getting enough sleep.
By taking steps to naturally boost your serotonin to happy levels, you can promote good mental health and overall well-being, allowing you to lead a happier, more fulfilling life.