The microbiome has a huge effect on your mental outlook: mood, emotions, sense of optimism or pessimism, your internal dialogues. Here is a recent study that highlights this effect.
In this study, 210 people with major depression, bipolar illness, or schizophrenia who had either attempted suicide recently (most within the past 4 weeks) or further in the past were compared to 72 healthy controls. Antibody levels to the yeast, Saccharomyces cerevisiae, the gliadin protein of wheat, and bacterial lipopolysaccharide, LPS (the cell wall component of Gram negative species such as those in dysbiosis and SIBO) were measured. Here is what they found:
The study is observational by necessity, as you cannot obviously assign participants to suicide or no suicide, so we have to be careful about discerning cause and effect. But the differences are so striking that the associations may indeed be real. (Recall that, with cigarette smoking, the increased risk for lung cancer and heart disease was established through observational studies, but the increased risk was so great that the observational evidence was sufficient.) It means that people whose bodies wage an immune response to yeast (as in beer and bread), the gliadin protein of wheat, and the LPS of pathogenic bacterial species may be at risk for suicide.
How to interpret this observation? I would take the development of antibodies to yeast, gliadin, and LPS as evidence of increased intestinal permeability, as higher levels of antibody response in the bloodstream requires that such antigens be blood borne to stimulate an immune response. It also suggests that components of diet—yeast and wheat/grains—can play a role in mental health. Other questions come to mind:
- Is the high antibody level to yeast just a marker for increased intestinal permeability or is there something intrinsically harmful about yeast consumption?
- Does the increased level of IgG against wheat gliadin suggest greater wheat intake? Does it suggest that an autoimmune process has been triggered by gliadin that may involve the brain?
- Are LPS serum levels, not just greater antibodies against LPS, also higher, suggesting the bacterial endotoxemia is present that may influence brain function and mood?
Few conclusions can be drawn from this limited study, but the results are so provocative that it is sure to prompt further exploration of the questions raised. I believe we can at least agree that suicide is an extreme case of the mind being hijacked by some process that impairs or turns off the basic instinct for survival, a powerful impulse. It is also a reminder that diet and the microbiome play a considerable role in mental health.