Ali Miller, RD, LD, CDE uses salivary hormone and urinary neurotransmitter testing from Labrix to guide her clinical treatment protocols. With food-as-medicine, she treats anxiety by reducing inflammation and optimizing digestion, providing the necessary nutrients for health.
Part of her therapeutic approach in the treatment of anxiety involves treatment of the gut microbiome, and with good reason: alterations in intestinal microbiota have been studied as an independent factor in the development of anxiety.
As she mentions in her book, The Anti-Anxiety Diet, the microbiome influences brain derived neurotrophic factor (BDNF). In the hippocampus, BDNF is associated with memory and learning, but recent evidence suggests that increased levels of BDNF in the hippocampus have anxiolytic and antidepressant affects. The Journal of Gastroenterology published a study in which researchers examined the influence of microbiota composition alterations on BDNF. When levels of BDNF elevated in the hippocampus secondary to improved microbial composition, anxiety rates decreased. 
Not coincidentally, 50% to 90% of patients with IBS show psychiatric comorbidity, including anxiety. Researchers questioned whether the behavioral changes are secondary to the disability imposed by chronic gastrointestinal symptoms, or whether they are a directly tied to the underlying dysfunction, including alterations in the intestinal microbiota. This study revealed that the influence of intestinal microbiota on brain chemistry and behavior was independent of the autonomic nervous system, gastrointestinal-specific neurotransmitters, or inflammation. It seems that the microbiota alone were correlated to the changes in behavior, for better or worse.
This is not the only study to suggest that intestinal microbiota directly affect behavior. Another study revealed anxiety-like behavior after introduction of pathogenic bacteria (Campylobacter jejuni) into the gut. Moreover, an in vivo study indicates that the intestinal microbiota influences the development of the hypothalamic–pituitary response to stress, with less ideal microbial states leading to a heightened stress response over time. Yet another study elucidates a heightened response to stress following the inoculation with enteropathogenic Escherichia coli. 
This same study showed that both the exaggerated response to stress and the GI inflammation noted was normalized with the introduction of the probiotic strain, Bifiodobacterium. Importantly, the researchers point out that the improved HPA response was partly corrected by reconstitution in early stages, but not improved by reconstitution at a later stage, implicating that exposure to microbes at an early developmental stage is required for the HPA system to be wired in a healthy manner.
Perhaps the other side of the same coin, a number of research papers have shown that physical and psychological stress can affect the composition of intestinal microbiota in rodents. It seems to be a bi-directional communication line. The multitude of studies described provides strong evidence that an impaired microbial landscape may be an underlying factor in the pathogenesis of anxiety. Understanding the preceding causes of an impaired microbiome can help to elucidate potential therapeutic interventions.
Ali Miller names the top drivers of dysbiosis she commonly sees in clinical practice: sterile c-section and formula bed babies, stress, antibiotic use, steroid use, antacids and or proton pump inhibitors, excessive alcohol, oral contraceptives, and diets high in sugar and refined carbohydrates. With a thorough history and appropriate laboratory testing, providers like Ali Miller are working from a root-cause approach and potentially avoiding the negative side effects of more aggressive interventions. 
As a Labrix provider you now also have access to the full array of Doctor’s Data tests, including the Comprehensive Stool Analysis, which can provide objective markers of gastrointestinal health, potentially giving way to etiologies underlying anxiety.