Microbial effects on mood and behavior, part of the gut-brain axis
Sorry, no overall summary yet.
Selected Scientific Literature
Foster and McVey Neufeld, 2013: Review of the evidence (almost entirely in mice) that the gut microbiota influences anxiety and depression. I think the evidence is compelling, but it always seems a bit of a stretch to me to definitively relate observable behaviors in mice (e.g. the light-dark test) to human conditions such as anxiety and depression. This is not to suggest that I doubt the existence of gut microbial effects on mood and behavior in humans - the neurotransmitters, and the effects of neurotransmitters, are too well conserved across mammals for me to think humans aren't affected. Besides, there is supporting evidence in humans, see below. (abstract only)
Collins et al., 2012: Broad review of evidence and possible mechanisms for how the gut microbiota may influence a range of conditions through different aspects of the gut-brain axis, including not only psychological conditions but irritable bowel syndrome and multiple sclerosis. (abstract only)
Cryan and Dinan, 2012: Review focusing on what different mechanisms might account for the gut-brain axis, with attention to evidence that the gut microbiota are involved. (abstract only)
Collins et al., 2012: Broad review of evidence and possible mechanisms for how the gut microbiota may influence a range of conditions through different aspects of the gut-brain axis, including not only psychological conditions but irritable bowel syndrome and multiple sclerosis. (abstract only)
Cryan and Dinan, 2012: Review focusing on what different mechanisms might account for the gut-brain axis, with attention to evidence that the gut microbiota are involved. (abstract only)
The studies below are some of the few in this area that involve humans.
Messaoudi et al., 2011: Effects of a probiotic on psychological assessments of healthy humans. (abstract only)
Benton et al., 2007: A study hoping to find that a probiotic relieved constipation and thus improved mood found instead that the probiotic improved mood without altering constipation. (abstract only)
Rao et al., 2009: Placebo-controlled, randomized clinical trial finding that a probiotic improved depression and anxiety in patients suffering from chronic fatigue syndrome. (full text)
Tillisch et al., 2013: Placebo-controlled, randomized clinical trial finding that yogurt with probiotics altered brain activity in regions associated with emotion and sensation. (full text)
Messaoudi et al., 2011: Effects of a probiotic on psychological assessments of healthy humans. (abstract only)
Benton et al., 2007: A study hoping to find that a probiotic relieved constipation and thus improved mood found instead that the probiotic improved mood without altering constipation. (abstract only)
Rao et al., 2009: Placebo-controlled, randomized clinical trial finding that a probiotic improved depression and anxiety in patients suffering from chronic fatigue syndrome. (full text)
Tillisch et al., 2013: Placebo-controlled, randomized clinical trial finding that yogurt with probiotics altered brain activity in regions associated with emotion and sensation. (full text)