Itcan be genetic and it can also be nutrition deficiency induced. Depends on the person (as always). It does exist
I commonly see schizophrenic patients with this issue. Interesting that gluten is also linked to schizophrenia (Bread madness). I haven't come across any research on the two together. Unfortunately, one of the leading minds on this topic recently passed away. RIP – Dr. Abram Hoffer.
All the best,