People who suffer from hypersensitivty to gluten are more likely to suffer from depression than other people who do not have this disorder. The reason for this is not yet known: perhaps some gluten slips into their diet - accidentally or not - and the depression is caused by the response to the inflammation. But it is also possible that they adhere stringently to their diet and consequently lack certain nutrients which causes depression.
This can be studied by comparing coeliac patients who stick their diets to fellow-patients who are little more easy going about their diets. Three Leiden researchers, with psychologist Nathalie van Hees as the first author, did just that.
As you can read in the Journal of Psychosomatic Research, they examined 2,265 coeliac patients, forty per cent of whom had suffered from depression at least once while around an eighth of the total group suffered from a depression during the study.
No difference was discovered between the easy-going and careful gluten-avoiders, but those who had stuck their diets for longer than five years suffered less from depression. This suggests that the issue of inflammation has something to do with it, but in this type of research, the case is very rarely straightforward: depressed people might be less likely to stick to their diet.