I'm not sure how you get that conclusion or questions from the article:
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Chemicals released by the gut microbiome can influence brain development, starting from birth. A review from 2015 states that the gut microbiome influences the central nervous system by "regulating brain chemistry and influencing neuro-endocrine systems associated with stress response, anxiety and memory function".[4] The gut, sometimes referred to as the "second brain", may use the same type of neural network as the CNS, suggesting why it could have a role in brain function and mental health.[5]
It's because it's a very new field. Few people would have ever thought diseases of the 'mind' could be related to the gut biome, so people are still actively researching exactly what is causing what. It's not because there's any question of whether this is an issue at all.
This is also an extremely important discovery, but it will have profound implications on modern health and diets. Everything from glyphosate to fake sugars has been argued to be harmless because we thought that they were largely inert. In reality they are having substantial impacts on the gut biome - the potential implications of this cannot be overstated, and so shooting wild and fast would be poorly advised.
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Chemicals released by the gut microbiome can influence brain development, starting from birth. A review from 2015 states that the gut microbiome influences the central nervous system by "regulating brain chemistry and influencing neuro-endocrine systems associated with stress response, anxiety and memory function".[4] The gut, sometimes referred to as the "second brain", may use the same type of neural network as the CNS, suggesting why it could have a role in brain function and mental health.[5]
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