The Effects of Psychological Stressors on the Intestinal Microbiota

The stress response affects virtually every organ in the body and constitutes a coordinated behavioral and physiological response to potentially threatening stimuli that may be physiological or psychological in nature. There is a substantial amount of research focusing on how the stress response affects health, but relatively few studies have focused on the ability of the stress response to affect indigenous populations of bacteria in the intestines, referred to as the intestinal microbiota. Research from our lab, and from others, have demonstrated that psychological stressors early in the life span significantly changes the levels of different types of microbiota that are shed from the intestines in the stool. In our studies, stress in young rhesus monkeys, and even in the prenatal period, led to a significant reduction in the levels of lactobacilli and bifidobacteria shed in the stool. In rodents, prolonged restraint stress resulted in a significant overgrowth of aerobic microbiota, particularly Gram-negative aerobes, in the intestines. Interestingly, there is increasing evidence that alterations in the microbiota are associated with a variety of diseases that are known to be exacerbated during periods of psychological stress, including irritable bowel syndrome and the inflammatory bowel diseases. Thus, our data provide a compelling rationale to test the hypothesis that stress-induced exacerbations of intestinal diseases are in part due to stress-induced alterations of the microbiota.