For a lot of years, there has been anecdotal evidence linking depression with gluten (along with more serious mental disorders, up to and including schizophrenia). The problem is, scientists in general, and doctors in particular pay little or no attention to evidence of this type. However, new discoveries have begun to throw light on what is going on.
Clinical depression appears to be linked with serotonin levels in the brain. This has led to the development of new types of anti-depressants, including SSRIs (Prozac is the most well known brand). These new drugs are not without their problems, however. Although initially hailed as dependency-free and safe, there has been a worrying rise in suicide amongst people taking these drugs, and certain patients have apparently had great difficulty in coming off them.
Serotonin is a natural substance which is produced in the body. This natural production appears to be impaired or reduced in various groups of people, including depressives.
The reasons for this impairment are not yet completely clear. However, 90% of the production of serotonin occurs in the digestive tract. So it begins to make sense that the food eaten might have an effect, either positive or negative, on serotonin production.
A report by Ron Hoggan M.A. & James Braly M.D. examines the relationship between depression and diet. They cite various studies carried out by Christine Zioudrou and later followed up by Fukudome and Yoshikawa. They point to morphine-like substances caused by incomplete digestion of proteins in cereal grains and dairy products (called "exorphins"). It is thought that these exorphins can be absorbed through the intestine, offering a possible explanation for the psychiatric effects experienced by otherwise healthy individuals.
Another report by Alessio Fasano and Carlo Catassi states that there is an "Asymptomatic Silent Form" of celiac disease. The term asymptomatic is a bit of a misnomer, as it refers only to the lack of positive test results. Symptoms of this form of gluten intolerance (which may not all be present) are: iron deficiency, a tendency to depression, irritability, or impaired school performance in children "feeling always tired," and easy fatigue during exercise, and reduced bone mineral density.
In a lecture he gave in 2002, James V. Croxton, M.A. talked about new discoveries relating to previously ignored cells in the brain called glial cells. These appear to be closely involved in the immune system, and directly affected by gliadin, part of the gluten found in wheat and other cereals.
Gluten-free diets (sometimes combined with dairy-free) have been used for autism, depression and schizophrenia, with some success. Even though the mechanism is still not fully clear, it does appear that there is a scientific basis for a connection between gluten and depression in susceptible individuals.
Further research may bring a cure. For the time being, though the only safe approach is to exclude gluten from the diet entirely.