In 1994 I was diagnosed with celiac disease, which led me to create Celiac.com in 1995. I created this site for a single purpose: To help as many people as possible with celiac disease get diagnosed so they can begin to live happy, healthy gluten-free lives. Celiac.com was the first site on the Internet dedicated solely to celiac disease. In 1998 I created The Gluten-Free Mall, Your Special Diet Superstore!, and I am the co-author of the book Cereal Killers, and founder and publisher of Journal of Gluten Sensitivity.
(snip. The articles goes on to explain that these peptides are biologically active & somewhat similar to opioid peptides.)
It is well known that casein (from human or cows milk) will break down in the stomach to produce a peptide known as casomorphine, which, as the name implies, will have opioid activities. Similar effects are noted with gluten from wheat and some other cereals ...in which the compounds formed are gluteomorphins (or gliadinomorphins).
So some of us who are gluten sensitive are also casein sensitive, and a gluten ingestion will affect brain activity.