Mental illnesses are the result of the interaction between genetic vulnerabilities and environmental factors. The microbial community is an environmental factor that is considerable in overall mental health outcomes.
In one way, mental health can affect the microbial community. Stress causes the release of pro-inflammatory cytokines from lymphocytes. Chronic stress prolongs this release of cytokines and at a certain level, the adaptive immune system decreases in function. This means that pathogens may have an easier time causing infections in the body and cause dysbiosis, disrupting the delicate balance between the good and the bad bacteria. It is worth noting that it is not stress that causes this disruption, but rather the behaviors that we engage in during stressful times. Stress is linked to binge eating and poor choices in food, and these behaviors cause dysbiosis.
In another way, the microbial community can affect mental and neurobiological health. Cells release protective secretions during a viral infection, such as beta-amyloid oligomers. Cerebrospinal fluid cleanses these oligomers from the brain, but factors like subsequent infections, which can be attributed to stress, can result in a buildup of these oligomers. The result is this buildup is the development of Alzheimer’s disease, a neurobiological disease that causes memory loss and possible death.
A different composition of the microbial community can affect mental health. Inflammatory bowel disease is linked with dysbiosis and so is Autism Spectrum Disorder. Perhaps it is due to a genetic vulnerability or behaviors during the gestational period that affects the microbiota is implied as a correlational factor. Bifidobacterium can be particularly helpful in reducing anxiety, as a study points out that mice with this bacterium have a lesser increment in stress hormone compared to germ-free mice.
It is a two-way street when the topic of mental health and microbial community is brought up. Thus, it is crucial that researches in both directions are approached and studied.
