You might want to look into the psychological affects of carbohydrate malabsorption. A lot of work has been done in that area regarding fructose, but fructans in wheat can have the same affect. If you are not gluten-intolerant (screening for celiac is important) and wheat gives you issues, this might be the mechanism. So we shouldn't always look towards gluten when having issues with wheat.

This isn't related to gluten specifically, but it makes the connection between inflammation (which can be caused by gluten) and depression. It explains a theory of the biological mechanism, called the Pathogen Host Defense or PATHOS-D theory. The theory posits that "the genes that predispose us to depression also protect us from infection." Chronic inflammation (indicating an ongoing immune response in the body/brain) is closely linked to depression. PATHOS-D asserts that depression is a consequence/side effect of a genetically rendered 'trigger happy' immune system, which itself has survival value. In other words, the potential for depression is present in individuals who have sensitive and reactive immune systems which is good for survival in some cases because you fight off infection before it can damage your system, but bad in other cases because the immune response interferes with brain functioning, causing depression. This would explain why depression, a hereditary phenomenon with social disadvantages but biological advantages, has been positively selected in the evolutionary process. It also suggests that reducing inflammation (e.g., no gluten) will alleviate depression.

Emily Deans, "Depression: A Genetic Faustian Bargain with Infection?" http://evolutionarypsychiatry.blogspot.com/2012/03/depression-genetic-faustian-bargain.html

I am so grateful to have found this question - because whilst I have no answer as to mechanism, at least I know that I am not alone in this and that I am not in fact losing my mind.

I have followed a gluten free diet for c.18 months, having finally identified an ongoing rash as dermatitis herpetiformis. It works, the rash has mostly disappeared. I am compliant, but realise I need to be even stricter w.r.t restaurant cross-contamination and avoid things like the Whole Foods salad bar - I have foolishly ignored the fact that utensils are shared between non-GF items etc. This I believe must be what triggered a current attack.

The DH makes this unambiguous for me; the rash has reappeared and I know I have been exposed to gluten. I have also been almost incapacitated by a desperate, awful, chronic depressive episode, complete with suicidal ideation. I have retained just enough sanity through this to recognise the possibility of a link between the two, which makes it more bearable. It will pass.

Thank you.

I know this thread is old but I stumbled on it and others probably will too. With that in mind, I just want to add to Sarah's comment above. I have been on a gluten free diet for about 3 years, and it's become very apparent that when I am exposed to gluten, one of symptoms of the reaction is a sudden onset of severe depression that gets me frighteningly close to having suicidal thoughts. I am usually considered a very stable and well bslanced person. This comes like clockwork about eight days (+/- a day) after eating gluten. It only lasts that day, and it's something I now expect, and so I usually just know to wait it out and not act on anything too deep and emotional. Its really frightening if you don't know what's causing it.

A big part of how you tolerate gluten will be how you expect to tolerate it.

I have binged on crazy stuff on an otherwise clean diet many times. When I thought that I was going to suffer for the next week, I did. When I thought that I could easily handle it, I did.

Paleo should make you stronger, not weaker. Hypochondria is the disease that kills most paleos, I imagine.