many psychiatric illnesses are immunological in nature through chronic low level inflammation. There is a plethora of evidence showing the link between gut microbiota and inflammation and studies on probiotic strains have revealed their ability to modulate inflammation and bring back a healthy immunological function. In this regard, by controlling inflammation through probiotic administration, there should be an effect of improved psychiatric disposition.
The authors bring up another reason why psychobiotics are so unique in comparison to most probiotics. These strains have another incredible ability to modulate the function of the adrenal cortex, which is responsible for controlling anxiety and stress response. Probiotic strains, such as Lactobacillus helveticus and Bifdobacterium longum have shown to reduce levels of stress hormones and maintain a calmer, peaceful state. There may be a host of other probiotic bacteria with the same ability although testing has been scant at best.