For me it's seemingly food intolerance to starch and sugar. About 4 days after consumption I'll get depression and suicidal ideation. I'll ruminate over work and whatever stresses me will be amplified.

For example I walk with a friend in the forest and shortly aware that I don't know where I am will turn into "he'll kill me" freakout... assistance dog would notice if something was off, and he's happily sniffing around and enjoying himself.