What Causes Depression? Apparently, not Serotonin Deficiency.

About one year into the pandemic, the renowned medical journal, The Lancet, published a study in which 34% of COVID-19 survivors were diagnosed with a new neurological or psychological condition within 6 months of infection.¹   It’s one of the many reasons why so many members of our community are struggling with low mood and mental health concerns right now. Many conventional treatments for depression hinge on the entrenched theory that serotonin deficiency causes depression. But this theory has been questioned many times, including very recently by authors of a large review paper, who emphasize that we have no convincing evidence for this established Serotonin Hypothesis.² It’s time to leave this myth behind us and seriously explore additional avenues of treatment for depression.

Depression Medication Success Rates

You might be familiar with the common antidepressant medications called “Selective Serotonin Reuptake Inhibitors” (or SSRIs). For people with moderate to severe depression, about half of the people treated with these medications will experience about a 50% improvement in symptoms. This appears to be the general consensus in pharmaceutical research. Benefits of medication for people with mild depression might be considerably less. In other words, hundreds of studies suggest that our standard treatment for depression works, (albeit not as well as some people thought it might). The question is: how do these medications work, if not by modifying serotonin?

Depression Medication and Placebo

Interestingly, 35% of people treated with placebo will also experience 50% improvement in their symptoms. We could jump to the conclusion (as many do) that depression must therefore be “all in your head”. Or, we could use this evidence to emphasize the untapped potential of thoughts and emotions for physical healing. We could also question the underlying assumptions about placebo.^3,4 (Some people are genetically predisposed to experiencing a benefit from a placebo. The study of how genetics affect placebo response is called “the placebome”. It calls into question what we think we understand about results from gold-standard clinical trials – especially in psychological research.)

Depression and your Microbiome

One recent small study found that people who took a multi-strain probiotic supplement alongside their anti-depressant medication, saw additional improvement in their symptoms after just one month.⁵ Another small study further identified positive changes in mood when taking a probiotic, and measured these changes with a brain MRI. ⁶ This data supports the growing evidence that our gut plays a critical role in mood. The gut has a unique and complex nervous system that communicates with the billions of bacteria and other healthy microbes there (collectively called our microbiome). It’s where 95% of our body’s serotonin comes from, along with a variety of other “brain” chemicals.

Depression and Inflammation

I couldn’t finish this article without highlighting the importance of addressing inflammation alongside mental health concerns. I wrote about it here 5 years ago and continue to follow the research for more practical ways to identify when inflammation could be a significant contributing factor to someone’s depression. For example, we can order a simple $5 blood test called C-Reactive Protein (CRP), that is a marker of inflammation. Researchers in Texas discovered that people with depression who have higher levels of CRP in their blood might respond better to a combination of medications that include more stimulating anti-depressants, compared to patients with normal CRP levels.⁷ And there’s plenty more opportunity for research in this area where mental health concerns are linked to inflammation caused by COVID-19 infection.

Holistic Treatment of Depression

Though research is promising where probiotics and anti-inflammatories are concerned, mental health is of course much more complex than this. It’s a culmination of whole-body health that also reflects social, spiritual, and historical experiences. Healing often requires multiple approaches, an open mind, and a broad lens.

If you’re struggling with depression, we welcome you to start exploring these resources as possible supports in your recovery:

Resources:

The Optimism test: Can you prevent depression and anxiety? The research says that yes, sometimes you can! By practicing the skill of optimism.

The Stress Questionnaire: Higher scores on this questionnaire are correlated with many health concerns, including depression. These scores can improve quickly – in as few as 4 to 8 weeks! If your score is high, consider using this questionnaire to monitor how well you’re doing every couple of months, after you’ve implemented some important life changes.

Heartmath biofeedback for mental health and stress

Mindfulness Questionnaire (coming soon to our Self Assessment page).

Shamanic Healing: Shamanic healing practices are often strongly informed by nature and address what we might call the “human spirit” as it relates to the emotional, mental and physical part of who we are.

Acupuncture: To address overall balance in the body, including where the immune system, digestive system, and hormones, impact brain health and emotional wellbeing.

*Photo by Matthew Henry on Unsplash 

References:

1. Taquet M., Geddes J.R., Husain M., et al. 6-month neurological and psychiatric outcomes in 236 379 survivors of COVID-19: a retrospective cohort study using electronic health records. The Lancet Psychiatry (2021); 8(5): 416-427. doi: 10.1016/S2215-0366(21)00084-5.

2. Mondrieff, 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.

3. Hall K.T., Lembo A.J., Kirch I., et al. Catechol-O-Methyltransferase val158met polymorphism predicts placebo effect in irritable bowel syndrome. PLoS One(2012); 7(10): e48135. doi: 1371/journal.pone.0048135.

4. Hoenemeyer T.W., Baidwan N.K., Hall K., et al. An exploratory analysis of the association between Catechol-O-Methyltransferase and response to a randomized open-label placebo trial for cancer-related fatigue. Psychiatry (2021). doi:10.3389/fpsyt.2021.684556.

5. Schaub, AC., Schneider E., Vazquez-Castellanos J.F., et al. Clinical, gut microbial and neural effect of a probiotic add-on therapy in depressed patients: a randomized controlled trial. Transl Psychiatry (2022); 12: 227. doi: https://doi.org/10.1038/s41398-022-01977-z.

6. Bagga D., Reichert J.L., Koschutnig K., et al. Probiotics drive gut microbiome triggering emotional brain signatures. Gut Microbes (2018); 9(6):486-496. doi: 1080/19490976.2018.1460015.

7. Jha M.K., Minhajuddin A., Gadad B.S., et al. Can C-reactive protein inform anti-depressant medication selection in depressed outpatients? Findings from the CO-MED trial. Psychoneuroimmunology (2017); 78:105-113. https://doi.org/10.1016/j.psyneuen.2017.01.023.