It’s Not Just in Your Head—The Microbiome and Depression

Psychiatric co-morbidities such as anxiety and depression are increasingly common among patients with chronic gastrointestinal (GI) disorders, such as chronic inflammatory bowel disease (IBD) and lower-grade inflammatory conditions such as irritable bowel syndrome (IBS). Extensive consumer marketing of yogurt and other commercial probiotics has catapulted awareness, prevention and treatment of gut disorders to one of the hottest topics in healthcare.

As a result, most doctors understand the importance of the microbiome for motility, disease prevention and serious illness. But recent scientific advances have shown that the arrant volume of the human microbiome is staggering. How staggering? A normally functioning human gut contains 100 times more genes than the entire human genome. Yet the ubiquity and diversity of cell types and functions are not well understood, leading many experts to view the microbiome as a unique and separate organ system—and thus a goldmine of untapped information regarding human health. For instance, microbial activity most certainly contributes to autoimmune disease, cancer and obesity—to name a few. Yet, the vast volume and heterogeneity of the microbiome suggests a much larger footprint. Pursuing a greater understanding of an individual’s microbiome is complicated by numerous variants including the obvious—diet. Yet the microbiome presents a novel avenue for improving personalized medicine and for the development of new nutritional interventions in disease prevention, including mental health.

Probiotics, Depression and Anxiety

In 2017, research by Pinto-Sanchez and colleagues studied the impact of an important microbiome on anxiety and depression. Bifidobacterium longum (BL) is a microaerotolerant anaerobe and is thought to be among the first colonizers of the human GI tract. As adults, BL is not significantly present in terms of volume, however, it is considered an essential gut flora due to its production of lactic acid, which we believe acts to prevent the growth of pathogenic organisms. As a probiotic, BL is non-pathogenic and can be used as a supplement in the human diet.

BL and Depression

Using a randomized, placebo-controlled, prospective study, the Pinto-Sanchez, et al, used the Rome III criteria to select 44 adults with IBS with concurrent anxiety and/or depression based on the Hospital Anxiety and Depression scale. After 10 weeks, administration of BL probiotic resulted in statistically significant reduction of depression, but not anxiety. Moreover, depressed participants reported “significant” improvement in their quality of life. Administration of BL probiotic was associated with changes in brain activity patterns within the limbic system, further confirming the biological roots of depression which opens the door even wider for new and novel approaches to treat this deadly disease.

The Limbic System is a loop of cortical structures–amygdala, hippocampus, ventral tegmental area, nucleus accumbens and cingulate gyrus. The limbic system plays a major role in emotion, reward and memory as the pleasure and aversion centers. Disruptions in limbic signals are associated with depression, anxiety and substance use disorders.

Why Does This Matter?

The concordance rate for depression and SUD is estimated between 45 and 60%—among treatment populations, it’s even higher. Clearly, there is much to learn about the microbiome and its effect on the brain, mental illness and Substance Use Disorder (SUD).

Not unlike sleep problems, GI distress is a common feature of Major Depressive Disorder (MDD), Anxiety Disorders, and SUD, particularly opioid abuse, dependence and withdrawal. Opioid receptors abound in the GI tract and react to exogenous opioids. Constipation is a common, co-occurring symptom among opioid abusers and addicts. Conversely, severe GI cramping, diarrhea, nausea and vomiting are central features of the opioid and alcohol withdrawal sequela.

For mental health and addiction professionals, evaluation of a patient’s GI health is an important component of treatment—and just good medicine. Patients in treatment for depression or addictive disease should receive nutritional assessment and specific dietary recommendations. Probiotics are well-tolerated and may be used under medical supervision to stabilize a patient’s motility and other GI symptoms. Stable gut flora is associated with improved physical and mental health and well-being.