About five years ago, after experimenting with some diet changes, I started having some pretty terrible digestive issues, like extremely bloating and indigestion. The issues would fluctuate, sometimes being much worse than others. Along with it came personality changes, like apathy, and they would also fluctuate along with the digestive issues. It's actually pretty scary how much it affected my brain. There are times when the apathy is so extreme I feel like a psychopath, and that comes from someone that once upon a time was vegan due to ethical reasons, so I am (or was) an empathic person. It really is mindblowing. The thoughts I have had and sometimes have would put me in a psychiatric hospital, thoughts I would have never imagined I would have.