The Biology of Mental Health: Understanding the Inner Workings of the Mind-Body Connection
Beyond Serotonin: Exploring the Diversity of Mental Health
While serotonin has long been associated with mental health, its role may not be as significant as previously believed [1].
The idea that low serotonin levels directly cause mental health issues and that boosting serotonin can cure symptoms is vastly oversimplified and even incorrect in most cases. While serotonin influences mood, the connection between serotonin and mental health is more complex than we originally believed. Selective serotonin reuptake inhibitors (SSRIs) are very often prescribed for the treatment of mental disorders. However, as highlighted in a recent systematic review in Nature Molecular Psychiatry (2022), ongoing research exploring their efficacy and underlying mechanisms suggests this may not be helpful or even harmful in many cases.
Research has shown that significant numbers of people exhibiting normal serotonin levels can still encounter mental health issues, and that those low serotonin levels do not necessarily exhibit depression or mental health issues. This suggests that mental wellbeing does not correlate reliably with serotonin levels.
It is essential to recognize the importance of personalized treatment approaches that consider multiple aspects of an individual's condition, rather than simply addressing serotonin.
In some people, SSRIs can help relieve certain depression symptoms, much like aspirin reduces fever symptoms. However, like aspirin does not fix the causes of pain, SSRIs do not directly address the underlying causes of depression.
This can partly be explained by the roles of another class of proteins that act downstream of serotonin and other well-known neurotransmitters that influence mental health. These are called second messengers, and they help transmit information around the brain and to the body. The interactions between second messengers are complex and relatively little understood, but we know they are of supreme importance in the functions of SSRIs and all other drugs that work on cognition.
Furthermore, the systematic review also pointed to very large studies examining genetic variations in the serotonin transporter gene, which is targeted by antidepressant medications like SSRIs. It was hypothesized that perhaps individuals susceptible to depression might exhibit gene-level differences in the receptor. However, no significant differences were found between individuals with depression and those without.
On the other hand, other studies reviewed in this analysis revealed a notable association with depression: the more stressful life events a person encountered (especially younger in life), the higher their likelihood of experiencing depression.
Based on their extensive review, the authors concluded that the vast majority of the data do not support the hypothesis that depression is caused by reduced serotonin activity or concentrations but that other factors beyond more important in the development of depression.
All this said, medications that affect serotonin, such as SSRIs, can still be effective for some individuals. However, taking a comprehensive and holistic approach to mental health that considers the broader context is crucial for a more accurate understanding and effective treatment of mental health conditions.
Can the bacteria in our gut contribute to the development of depression?
Recent research indicates that gut microbiota may have a massive impact on the development and treatment of depressive disorders, and it has been observed that the severity of depressive symptoms differs among ethnic groups.
As highlighted in a recent expert review [2], from the time we are born, we begin to develop and maintain a complex community of beneficial bacteria and other microorganisms inside our bodies. These microscopic organisms, numbering in the trillions, are more numerous than our own human cells! This thriving community of microorganisms is collectively known as our microbiome. We all have a thriving microbiome that covers every surface of our skin and the linings of internal organs that contact matter from the outside world: our intestines, lungs, sinuses, mouths, inner ears, etc.
Our microbiome consists of a diverse range of microorganisms, some beneficial and others potentially harmful. Maintaining a healthy and balanced microbiome is essential for overall well-being, protecting against significant health risks like heart disease, obesity, diabetes, arthritis, and even depression. The microbiome of the gastrointestinal tract, which spans the mouth to the rectum, is where the majority of these microorganisms reside. This population plays a crucial role in digestion, hormone regulation, and boosting the immune system, thereby contributing to improved mental wellbeing.
In fact, the impact of gut microbes extends far beyond what we previously believed even 10 years ago. Over the past two decades, research has revealed that these microbes maintain continuous communication with the brain, and that gut microbes even have the ability to produce neurotransmitters, influencing mood and emotions. Additionally, cells in the gut lining have the capacity to detect these neurotransmitters and relay signals to the brain.
Collectively, this bidirectional communication system between the gut and the brain is referred to as the gut-brain axis, and it is heavily influenced by the gut microbiome. Imbalance or “dysbiosis” has been associated with various mental health disorders via inflammation and altered neurotransmitter function. An unhealthy microbiome is often linked to systemic inflammation and poor mental health, and is now thought to contribute to many common diseases.
According to the National Institutes of Health, chronic inflammation is linked to mental health conditions like depression, anxiety, and schizophrenia. It affects neurotransmitters, neuroplasticity (the brain's ability to change and adapt), and mood-regulating chemicals in the body.
Chronic stress triggers the body's stress response, raising pro-inflammatory molecules called cytokines. This disrupts gut health by changing the gut microbiota and weakening the intestinal barrier, causing further inflammation.
Probiotics, the beneficial bacteria that promote a healthy gut microbiome, have recently shown promise in reducing symptoms of anxiety, depression, and stress. By influencing the communication between the gut and the brain, these live microorganisms positively impact mental health. Research suggests that specific probiotic strains can help restore gut microbiota balance and enhance overall well-being, including a happier, healthier brain. Not all probiotics are created equal however, so talk to your doctor or a Maka health expert about the best brands and the best strains for your individual needs.
Prebiotics, dietary fibers that serve as nourishment for beneficial gut bacteria, support the growth and activity of these bacteria, which can positively impact mental health. By contributing to a healthier gut microbiota composition, prebiotics play a role in promoting mental well-being.
A third way to support a healthy microbiome is to ensure you have the greatest microbial diversity possible: the more diverse the bacteria in our bodies, the better. One effective way to increase diversity is by eating a wide variety of plant-based foods. Studies reveal that individuals who include at least 30 different plant-based elements in their diet each week have a greater variety of gut bacteria. This diversity is associated with improved weight management, heart health, and mental well-being. Just be sure to choose organic produce, especially when it comes to the ‘dirty dozen’ - the most pesticide-heavy produce - as pesticides like glyphosate disrupt the microbiome.
So, by prioritizing gut health through a balanced lifestyle, consumption of probiotics and plenty of dietary fiber in the form of organic produce and/or prebiotic supplements, you can support a healthy gut microbiome and your overall mental and physical wellbeing. Mental health conditions are complex, and a comprehensive approach that considers both the mind and the gut is essential for overall vitality.
References:
Moncrieff, J., Cooper, R.E., Stockmann, T. et al. The serotonin theory of depression: a systematic umbrella review of the evidence. Mol Psychiatry (2022). https://doi.org/10.1038/s41380-022-01661-0
Shoubridge, A.P., Choo, J.M., Martin, A.M. et al. The gut microbiome and mental health: advances in research and emerging priorities. Mol Psychiatry 27, 1908–1919 (2022). https://doi.org/10.1038/s41380-022-01479-w
This article is provided for educational and informational purposes only and does not constitute providing medical advice or professional services. The information provided should not be used for diagnosing or treating a health problem or disease. Always seek the advice of your doctor or other qualified health provider regarding a medical condition. If this article features the advice of physicians or medical practitioners, their views are their own, and do not necessarily represent the views of Maka.
