Debate exists about how soon knowledge about the gut-brain axis will bear fruit. Yet the microbiome-gut-brain axis is a hot topic of scientific investigation and several companies around the globe are actively pursuing gut microbiome therapies that focus on brain-related conditions.
Here’s a quick overview from our lab scientists on various areas of brain health and the evidence linking each one to the gut microbiota.
General early life neurodevelopment
Dozens of human studies and mechanistic animal studies support the relevance of gut microbiota to normal behaviour and neurodevelopment; however, these studies are not always specific to neurological development, and the observed effects could be confounded by many other factors that affect the early life microbiome.
Autism spectrum disorders
Although there are known genetic contributors to autism spectrum disorders, both human and animal studies show a connection between gut microbiota and both gastrointestinal symptoms and social deficits in these individuals.
A moderate level of evidence links anorexia with gut microbiota; no mechanistic studies have been completed to date.
Attention deficit hyperactivity disorder (ADHD)
A low level of evidence implicates gut microbiota in ADHD; this disorder may also be linked to diet, but much more research needs to be undertaken.
A growing number of human studies as well as mechanistic animal studies have found the gut microbiota has immunomodulatory effects that may affect multiple sclerosis (MS) disease progression. Transfer of the microbiota from a human with MS to a mouse increases MS-like symptoms.
Post-traumatic stress disorder (PTSD)
Moderate evidence and one human study connects the gut microbiota with PTSD; further research may explore the mechanistic role of chronic inflammation as well as cortisol and dopamine regulation.
A high level of evidence links gut microbiota with depressive symptoms; probiotics may improve depression in both humans and animals.
While the studies on anxiety overlap with those on depression, some reports in both animals and humans show potential of microbiota modulation -- for example, through probiotics -- for improving symptoms of anxiety.
Extreme fatigue may also be linked with the gut microbiota, although diet appears to be a major confounding factor and more research is required.
Many studies in humans link Parkinson's disease (PD) with the gut, but chronic constipation in those with PD is a possible confounding factor. Mechanistic evidence to back these findings is just beginning to emerge.
Emerging evidence shows the Alzheimer's-gut connection: in mice, Alzheimer's-like symptoms are altered by microbiome manipulation.
A round table discussion at the Global Engage Microbiome R&D and Business Collaboration Forum on Thursday, November 2nd, led by CEO Malcolm Kendall, will explore what we know about the gut-brain axis and how soon it could yield breakthrough therapies.