User:Dogfishbennet/sandbox

Title: Anxiety and the Gut-Brain Axis

Subsection under "Anxiety" > "Risk-factors" > "Neuroanatomy"

The microbes of the gut can connect with the brain to affect anxiety. There are various pathways along which this communication can take place. One is through the major neurotransmitters. The gut microbes such as Bifidobacterium and Bacillus produce the neurotransmitters GABA and dopamine, respectively. The neurotransmitters signal to the nervous system of the gastrointestinal tract, and those signals will be carried to the brain through the vagus nerve or the spinal system. This is demonstrated by the fact that altering the microbiome has shown anxiety- and depression-reducing effects in mice, but not in subjects without vagus nerves.

Another key pathway is the HPA axis, as mentioned above. The microbes can control the levels of cytokines in the body, and altering cytokine levels creates direct effects on areas of the brain such as the hypothalmus, the area that triggers HPA axis activity. The HPA axis regulates production of cortisol, a hormone that takes part in the body's stress response. When HPA activity spikes, cortisol levels increase, processing and reducing anxiety in stressful situations. These pathways, as well as the specific effects of individual taxa of microbes, are not yet completely clear, but the communication between the gut microbiome and the brain is undeniable, as is the ability of these pathways to alter anxiety levels.

With this communication comes the potential to treat anxiety. Prebiotics and probiotics have been shown to reduced anxiety. For example, experiments in which mice were given fructo- and galacto-oligosaccharide prebiotics and lactobacillus probiotics have both demonstrated a capability to reduce anxiety. In humans, results are not as concrete, but promising.