In 2013, 1 in 6 American Adults Self-Reported Psychiatric Drug Use1

Antidepressants and anti-anxiety medication make up the largest percentage of prescriptions in the United States.1 Americans are currently spending $12 billion to manage mood, and the demand continues to rise. Most of these drugs are targeted at the neurotransmitter serotonin designed to increase availability of this circulating chemical thereby addressing the prevailing opinion that most psychiatric anomalies are attributable to a chemical imbalance in the brain.

But newer research is pointing towards another cause. As the links between the gut and the brain are elucidated, more interest is focused on inflammatory response. In fact, 70 to 90% of patients who seek gut health support also have psychiatric complaints, suggesting a correlation.2

Inflammation

Studies have been conducted that link inflammatory markers to mental health. For otherwise healthy individuals, inflammatory markers including TNF-a, IL-6 and CRP are consistently elevated in individuals with persistent low mood.3 In fact, when pro-inflammatory cytokines are directly administered, mood reactivity is proportional. The consistent presence of inflammation also reduces the expression of brain-derived neurotrophic factor (BDNF), which is critical for neuroplasticity appropriate stress response.

So How Are So Many People Experiencing Such a Consistent State of Inflammation?

In 2013, one research team linked lipopolysaccharides (LPS) with mood-related symptoms.4 LPS are antigens produced by dysbiotic intestinal flora and can penetrate the tight junctions of the epithelial barrier, particularly when “leaky gut” is present. Once in the bloodstream, LPS increases inflammatory cytokine production, leading to cyclic inflammation, insulin resistance through activation of toll-like receptor 4 (TLR4), and even obesity.5 In addition, LPS can speed up the enzyme indoleamine-2,3-dioxyegenase (IDO) in the kynurenine pathway, which breaks down tryptophan, the sole precursor of serotonin.

Tryptophan Metabolism

Tryptophan is an essential amino acid that is metabolized into proteins, serotonin, melatonin or into the kynurenine pathway. A healthy microbiome plays a significant role in tryptophan metabolism, utilization, synthesis, and serotonin production.6 Increased IDO activity has been correlated with low mood, and kynurenine can trigger an anxious reaction when administered by itself. On the other hand, kynurenic acid, “produced by commensal intestinal microbiota and found in traditional foods (honey, green vegetables, tubers), is readily absorbed from the GI tract and has been reported to have anxiolytic activity when administered.”4

There are even species of bacteria that can synthesize serotonin from tryptophan directly. These bacteria are named in the reference citations below, but among them is the commonly supplemented species Lactobacillus plantarum. In fact, many probiotic strains have been found to positively support mood and stress response.

Bifidobacteria have also shown positive mood effects. For example, Bifidobacterium longum improved the reported mood of patients struggling with gastrointestinal symptoms.7 In experimental animals, Bifidobacterium infantis has also been associated with reduction in inflammatory response, increased plasma tryptophan, and increased kynurenic acid levels.8

Changing Behavior

Increasingly, researchers are correlating microbiome characteristics with mood and behavior. In a French study, researchers noted “significant improvements” in day-to-day emotional regulation, as well as lowered levels of the stress hormone cortisol, among otherwise healthy adults taking a daily probiotic supplement vs. placebo.9 In another recent study, supplementation with a multi-species probiotic blend resulted in significantly reduced cognitive reactivity to sad mood including reduced rumination.10

This line of research will undoubtedly continue for some time still, but there is growing acceptance for the use of probiotics as adjunctive support to first-line care for cognitive and mental health.

 

Klaire Labs guest author:

Dr. Jessica Brandes

Jessica is a board-certified Naturopathic Doctor who earned her doctorate from the CNME-accredited National College of National Medicine. A former New Yorker, Jessica did her undergraduate work at NYU. She is a member of the AANP and the OANP and holds a certification in the use of advanced IV treatments from the IIVNTP.

 

 

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