Prevalence of Depression & Anxiety in the U.S.

Depression and anxiety are two of the most common mood disorders in the United States – 21 million US adults have been diagnosed with depression and 40 million with anxiety as of 2021.1,2 Both conditions have been steadily increasing over the past 10 years.3

The Link to Inflammation

Typically, we are most focused on the various feelings involving depression and anxiety. Perhaps we have identified genetic and environmental circumstances contributing to our state, but how often do we consider inflammation as part of the problem? All too often, the inflammatory link is overlooked.

The neuroinflammatory association to these mood disorders has actually been well documented.4 Researchers have observed mood changes in both human and animal models in the presence of inflammatory proteins called cytokines. Your immune system uses cytokines to signal that it’s time to fight infection or repair tissue. The big question is, aside from viral or bacterial infections, where else could the proinflammatory cytokines be coming from? One critical organ system to consider is the digestive system.

The Gut’s Role

Leaky gut syndrome is a condition of the gastrointestinal tract (stomach, small and large intestine) in which the normal, healthy, tight junctions of the epithelial cells become compromised or “leaky,” allowing toxins, microbes, and poorly digested proteins into the bloodstream. This is commonplace in the US due to the Standard American Diet (SAD)—low in fiber, vegetables, and fruits, and high in saturated fats, processed foods, and refined sugar. Eating inflammatory foods damages the gut lining, setting up for imbalances that disrupt neurotransmitters and the limbic system. 

The neuroinflammatory triggers alter brain chemistry, activating the excitatory-inflammatory process leading to depression and anxiety. In fact, your first signs of gut inflammation may actually be feelings of anxiety and depression. These may occur even before any gas, bloating, indigestion, loose stool, or constipation. 

A recently published meta-analysis about GI inflammation and mental health found a strong connection between the inflammatory response, release of key cytokines and low levels of the “happy” neurotransmitter serotonin; and higher rates of depression. The diagnosis of Major Depressive Disorder was higher in individuals with the high inflammatory cytokine response.5

The Microbiome

Our gut is also the home of trillions of microorganisms—our microbiome. When the tissue is inflamed, our flora has to adapt too. Healthy, diverse beneficial bacteria, or probiotics, cannot grow well on inflamed tissue. Gut inflammation decreases the diversity of the flora and leads to overgrowths of some species in the small intestine and to yeast overabundance. 

Good gut flora actually work for us, activating vitamins that are cofactors in neurotransmitter biochemistry. For example, serotonin comes from the amino acid tryptophan, which you get primarily from eating meat. When leaky gut and poor gut flora occur, amino acids like tryptophan don’t get absorbed. The same goes for B vitamins and other important cofactors. These cofactors are the car keys to operating the enzymes that balance out neurotransmitters.

Healing the Gut

Rest assured, there is good news! Throughout even the last five years, probiotics have changed to create effective therapeutic advantages for people with leaky gut. Ortho Biotic from OrthoMolecular is a shelf-stable formula with lactobacillus, bifidobacteria, and S. boulardii, three key probiotic families that aid in stabilizing the gut flora. It has been observed that certain strains of lactobacillus and bifidobacteria are low in people with mood disorders.6 In addition, MegaSporebiotic was one of the first bacillus probiotics – key species studied for their immune-modulating abilities. Both formulas are important for increasing diversity of the gut flora. 

To help minimize gut inflammation from the SAD diet, I often use Digestzymes by Designs for Health or Intolerance Complex by Enzyme Science. Both formulas help reduce the inflammation from problematic foods which helps reduce the cytokine response produced in the bowel. Both formulas can be used as needed or in an ongoing way to support bowel healing. Remember, in depression and anxiety, using supplements like Digestzymes and Intolerance Complex may help stabilize mood because we are decreasing the inflammatory cause in the gut. If there is depression or anxiety, there is gut inflammation. 

A Two-Way Street

We want to start thinking about depression and anxiety as, in large part, inflammatory issues. Reducing bowel inflammation is key in improving mental health. You want your GI tract to be the entry way for great nutrition, not the source of your inflammation. Hopefully one day the Standard American Diet will not be synonymous with inflammation. But, until then, understanding and solving leaky gut must be factored in with mental health treatments. 

If you have comments and/or questions about this blog, email us at

Amy Nelson, ND* received her Naturopathic Doctorate from the National College of Natural Medicine in Portland, OR where she studied nutrition, homeopathy, herbal and functional medicine. In addition, Dr. Nelson was the Associate at The IBS Treatment Center in Santa Monica where she treated irritable bowel syndrome and complex food allergies. Dr. Nelson utilizes her experience in natural medicine to address female and male hormonal imbalances, mental health, and digestive disorders. Amy is available for consultation at:

*Although licensed in other states, Naturopathic Doctors are not currently licensed in Texas. To support licensure efforts, please visit


  2. Anxiety Disorders – Facts and Statistics. Anxiety & Depression Association of America. Accessed 9/7/2023.
  5. Dowlati Y, Herrmann N, Swardfager W, Liu H, Sham L, Reim EK, et al.. A meta-analysis of cytokines in major depression. Biol Psychiatry. (2010) 67:446–57. 10.1016/j.biopsych.2009.09.033 [PubMed] [CrossRef] [Google Scholar] [Ref list]
  6. Sonali S, Ray B, Ahmed Tousif H, Rathipriya AG, Sunanda T, Mahalakshmi AM, Rungratanawanich W, Essa MM, Qoronfleh MW, Chidambaram SB, Song BJ. Mechanistic Insights into the Link between Gut Dysbiosis and Major Depression: An Extensive Review. Cells. 2022 Apr 16;11(8):1362. doi: 10.3390/cells11081362. PMID: 35456041; PMCID: PMC9030021.