>>514161594
A lot of mental illness is actually credibly linked to the gut-brain axis and this didn't even become scientific interest until the 21st century. Diet, lifestyle, antibiotics, etc. all have a direct effect on gut flora and even medium-to-high functioning autism can potentially be treated with fecal microbiota transplantation. There's a good chance that modern industrialized life was to blame for so much and it was always just written off as holistic bullshit because we didn't have the scientific proof yet.