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I’d Like A Personality Transplant, Please!

Do you know what's in your digestive system?

Nurses General Nursing Article   posted

Specializes in Oncology, Home Health, Patient Safety.

This is the third in a series about the gut microbiome (I know, catchy concept – who wants to read about the bacteria living in your digestive system? But seriously, keep reading!). Recent research has implicated the microbiome in colitis, IBS, obesity, depression, autism, cancer, Alzheimer’s and diabetes. This article explores how the bacteria living in your gut play a role in mental health and provides resources for accessing therapies with microbiota.

I’d Like A Personality Transplant, Please!
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For Part One of this series go to Trust Your Gut?...


Recent research has shown that bacteria living in your gut are linked to anxiety, depression, schizophrenia and autism. It makes sense - we’ve all said it at some point, “I have a gut feeling” or, “I have butterflies in my stomach.” For me, there have been times when I’ve been so stressed out that my stomach hurts. In a 2004 study of germ-free mice (genetically homogeneous laboratory mice, birthed and raised in an antiseptic environment), researchers found an exaggerated response to stress compared to those with germs. Something about the presence of microbiota in the gut protected the mice from stress-related symptoms.1 This research led to the term “gut-brain axis”, revealing a bidirectional link between the central nervous system and the gastrointestinal system. These two systems communicate via neural pathways, neurotransmitters and hormones, creating a direct link between cognitive and emotional centers. As I discussed in a previous blog post, the microbes living in our gut are fairly unique to us – this unique microbial composition is known as an enterotype.2 Our enterotype doesn’t seem to be related to genetics or gender, but rather to environmental factors like diet, stress or antibiotic use. 3


There are over 1000 species of bacteria living in your digestive tract. They help you digest food, produce needed vitamins and some of them secrete chemicals that impact brain function, like short-chain fatty acids (SCFA) and bile acids. Much of the serotonin in your body is produced by your gut, which contributes to happiness and controls your sleep-wake cycles. The neurotransmitter GABA is also produced in the gut – it controls feelings of fear and anxiety. So, your brain affects your gut health and your gut affects your brain health.1&3 There’s promising research on the impact of the microbiome on anxiety, autism and Alzheimer’s just to name a few, but I’m going to focus in on depression.


Major Depressive Disorder is the leading cause of disability in the U.S. for people between the ages of 15 and 44. It affects more than 16 million American adults, or 6.7% of the U.S. population.4

Depression can cause severe symptoms that affect how you feel, think and handle daily activities like sleeping, eating or working. It is caused by a combination of genetic, biological, environmental and psychological factors.


Depression is usually treated with a combination of medications and psychotherapy. Unrelieved depression may be treated with electroconvulsive therapy (ECT) and other brain stimulation therapies like repetitive transcranial magnetic stimulation and vagus nerve stimulation (the vagus nerve is an eight-lane highway linking the central nervous system and the gastrointestinal system).

Antidepressants are the main medical treatment modality. No one size fits all and you may have to try several different medications before finding the right one. In addition, they can take between 2-4 weeks to work. St. John’s wort has also been used, though it is not FDA approved with serious safety concerns. Omega-3 fatty acids and SAMe also under study, but not proven safe and effective for routine use.5

How effective are antidepressants? 20-40% of people using other forms of treatment (not antidepressants) experience relief from symptoms within 6-8 weeks, compared to 40-60% of those treated with antidepressants. Antidepressants are better than a placebo, but for patients with severe depression, the benefits may be minimal or nonexistent. Research is showing non-medical therapies can be just as effective. Exercise, Psychotherapy, also known as talk-therapy like cognitive-behavioral therapy (CBT), interpersonal therapy (IPT) and problem-solving therapy are traditional options.6

I found a recently approved treatment option that is brand-new and thought I would share it here. There is a ketamine-like nasal spray that has just been approved for depression that looks promising.7

Be sure to have the SAMHSA Substance Abuse and Mental Health Services Administrationin your resource list for patients.8 SAMHSA’s National Helpline – 1-800-662-HELP (4357)They provide free, confidential 24/7, 365 day-a-year treatment referral and information service.


Human and animal studies of introducing foreign bacteria show similar reductions in anxiety and depressive symptoms.3 In 1998, researchers observed anxiety-like behavior in rats fed a bacteria called Campylobacter jejuni. They discovered that the anxiety was accompanied by signaling along the vagus nerve. In a 2017 review of clinical trials (actual humans!), most of the studies found positive results on measures of depressive symptoms. All the trials used different strains, doses and length of treatment so further study is needed.9


A new class of probiotics, known as psychobiotics or psychomicrobiotics has emerged in the last decade. They are being studied as a nontoxic intervention for psychiatric conditions. There are various ways to introduce probiotics into the gastrointestinal system. I discussed Fecal Microbiota Transplant (FMT) in another blog post10, however, FMT is not attractive for several reasons. Drug companies aren’t interested in researching something that won’t provide a profit, and patients need to be healthy enough to undergo sedation and a colonoscopy and be willing to receive fecal matter from a donor. Researchers are exploring ways to freeze dry FMT so it can be given orally.11 Probiotic capsules are another option. They are living microorganisms used as supplements. The bacteria are freeze-dried and put into capsules. This option is more appealing to patients and drug companies for obvious reasons; however, this delivery method has been shown to take longer and be less effective.2


If you are interested in learning more about how microbiome therapy could be useful to you, talk to your primary care provider and consider finding a provider who specializes in integrative health – often physicians trained in integrative health have more knowledge of alternative treatment options. I believe if researchers had access to the enterotype of the 16 million Americans living with depression, it would go a long way toward finding new treatment options.

Want to know which microbes live in your gut? Visit the American Gut Project11.

There are many clinical trials happening right now, so be sure to take a look and see if you or someone you care for might qualify. Visit ClinicalTrials.gov. I went there and found the following clinical trial using FMT for depression: Oral frozen fecal microbiota transplantation (FMT) capsules for depression: a double-blind, placebo-controlled, randomized parallel group study: To assess the efficacy and safety of oral frozen fecal microbiota transplantation capsules for patients with moderate to severe depression.12

Click HERE for a list of current studies on the microbiome.

And HERE is a link to the Human Microbiome Project.

The overall mission of the HMP is to generate resources to facilitate characterization of the human microbiota to further our understanding of how the microbiome impacts human health and disease.


  1. The Role of Microbiome in Central Nervous System Disorders (2004). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4062078/
  2. https://allnurses.com/using-bacteria-control-your-weight-t700327/
  3. Gut microbiota’s effect on mental health: The gut-brain axis (2017) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5641835/:
  4. The Anxiety and Depression Association of America https://adaa.org/about-adaa/press-room/facts-statistics
  5. National Institute of Mental Health https://www.nimh.nih.gov/health/topics/depression/index.shtml
  6. How Effective are Drug Treatments for Depression? (2017). https://health.usnews.com/health-care/patient-advice/articles/2017-04-28/how-effective-are-drug-treatments-for-depression
  7. Ketamine-like nasal spray approved in spring of 2019: https://www.healthline.com/health-news/fda-approves-new-nasal-spray-for-depression
  8. SAMHSA https://www.samhsa.gov/find-help/national-helpline
  9. Appleton, J. (2018). The Gut-Brain Axis: Influence of Microbiota on Mood and Mental Health. Integrative Health, 17(4) 28-32
  10. https://allnurses.com/trust-your-gut-a-fecal-t699155/
  11. The American Gut Project http://americangut.org/
  12. Fecal Microbiota Transplant and Depression https://clinicaltrials.gov/ct2/show/NCT03281044

BIO: Dr. Kristi Miller, aka Safety Nurse is an Assistant Professor of nursing at USC-Upstate and a Certified Professional in Patient Safety. She is also a mother of four who loves to write so much that she would probably starve if her phone didn’t remind her to take a break. Her work experiences as a hospital nurse make it easy to skip using the bathroom to get in just a few more minutes on the computer. She is obsessed with patient safety. Please read her blog, Safety Rules! on allnurses.com. You can also get free Continuing Education at www.safetyfirstnursing.com. In the guise of Safety Nurse, she is sending a young Haitian woman to nursing school and you can learn more about that adventure: https://www.gofundme.com/rose-goes-to-nursing-school

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I loved this article!!! We have been learning about alternate therapies to antidepressants in class. I find it unbelievable how regularly antidepressants are prescribed with success rates that I personally feel are unimpressive comparably. Looking forward to seeing more research on this come up in the future, thank you for sharing!

SafetyNurse1968, ADN, BSN, MSN, PhD

Specializes in Oncology, Home Health, Patient Safety.

23 hours ago, aefigari said:

I loved this article!!! We have been learning about alternate therapies to antidepressants in class. I find it unbelievable how regularly antidepressants are prescribed with success rates that I personally feel are unimpressive comparably. Looking forward to seeing more research on this come up in the future, thank you for sharing!

Thanks, aefigari, I hope you saw the bit about the ketamine nasal spay as well - I'm so excited about that as an emerging treatment option.


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