Mental Diet and Disease.

>I read somewhere the the French Revolution was blamed on temporary mass
>schizophrenia brought on by the gluten in the bread that the peasants ate
>- some sort of fungus that had grown in it due to poor storage.

The big threat to grain eaters in Europe used to be alkaloids from certain fungal toxins in grains collectively known as ergot alkaloids and ergotamines. They cause epidemics of peripheral gangrene of the limbs. I do not have any data on schizophrenia in this context, although ergot alkaloids have been used to treat migraines and enhance delivery in obstetrics. In much of the balkans they also have fungal toxins that cause kidney and liver problems. (This is found in most countries where modern antifungal spraying is not economically feasible). Also in periods of starvation (esp war) Lathyrism caused by neurotoxin from chickling peas is well known.

However, there is a precedent for excitotoxic amino acid like compounds from food causing Central nervous disease in certain pacific islands such as Guam with vastly increased incidence. The Chamorros of the marianas and micronesia ate the seed of a false sago plant Cycas Circinnalis, from which the compound beta-N Oxalamio-L -alanine could be isolated. This causes amyotrophic lateral scelerosis, parkinsonism and Alzheimer -type dementia with considerable frequency (1,2)

References:
1: Lewin R (1987) Environmental hypothesis for brain diseases strengthened by new data. Science 237:483-484.
2: Spencer PS et al (1987) Guam amyotrophic lateral Sclerosis
-Parkinsonism
-Dementia linked to a plant excitant neurotoxin.Science 237:517-522.