Microbial diversity seems to be the key indicator to a healthy personality. Strong microbial diversity supports good mental health while a low microbial diversity points toward mental health problems such as autism or neuroticism. "Personality is both inherited and influenced by one’s environment. And the environment inside humans may matter just as much as the external environment", says Katerina Johnson in the Inverse article, and a research associate at Oxford. It is believed based on ongoing research that a lack of the Akkermansia, Lactococcus, and Osciollospir bacteria in our gut shows a tendency to autism, says the report (source: https://www.inverse.com/mind-body/microbiome-mental-health-study-links-gut-bacteria-personality/amp ). Conversely, a study of primates shows that social interactions can promote gut microbiome diversity, adds Dr. Johnson (see https://psychcentral.com/news/2020/02/13/gut-bacteria-may-be-linked-to-personality-traits/154172.html ). So the research suggests it goes both ways, even though it is not explicitly stated in these articles. We are predisposed in part to being social or anti-social based on the pre-existing level of microbiome diversity in our gut, but we can promote healthy microbiome diversity in our gut by being more social.
BBC Science reported in December 2019 that probiotics and prebiotics by nurturing and nourishing our gut bugs can help ease stress and anxiety, even aid in reducing other mental health risks. (See article, https://www.sciencefocus.com/the-human-body/psychobiotics-your-microbiome-has-the-potential-to-improve-your-mental-health-not-just-your-gut-heath/amp/ ). So yes, be at ease; the bottom line is we do have self determination; we can steer and shape and mold our own personality. . . with a little help from our microbiome friends.