[15] Dohan proposed a genetic defect wherein individuals are incapable of completely metabolizing gluten and casein as a possible cause for schizophrenia.
Dohan hypothesized that elevated peptide levels from this incomplete metabolism could be responsible for schizophrenic behaviors.
These peptides were speculated to arise from incomplete digestion of certain foods, in particular gluten from wheat and certain other cereals and from casein from milk and dairy produce.
Reichelt hypothesized that long term exposure to these opiate peptides may have effects on brain maturation and contribute to social awkwardness and isolation.
On this basis, Reichelt and others have proposed a gluten-free casein-free (GFCF) diet for those with autism to minimize the buildup of opiate peptides.