The role of nutritional deficits in depression in patients with coeliac disease

Coeliac disease (CD) is a genetically predisposed intolerance for gluten, which
affects approximately 0.5 - 1% of the population. There is no cure for CD,
however a gluten-free diet improves symptoms. During the past decades it has
become clear that CD is associated with an increased prevalence of several
neurological and psychiatric disorders, including cerebellar ataxia, peripheral
neuropathy, epilepsy, dementia and depression. Some studies find a rapid
improvement of depressive symptoms after initiation of gluten-free diet,
whereas others find no improvement or even worsening of depression rates.
In a survey among Dutch CD patients, we found that 37.7% (N = 715) had a
lifetime diagnosis of depression, which is more than twice the lifetime
prevalence of 15.4% in the general population (Bijl, Ravelli & van Zessen,
1998). We also identified 163 participants with a probable diagnosis of current
depression despite a good to very good adherence to gluten-free diet. Of the
people with a lifetime depression, 28.2% had the first onset of probable
depression after the start of the gluten-free diet. This is an unexpected
finding considering the general assumption in the field that depression in CD
is causes by the extended period of illness before diagnosis and treatment. The
underlying mechanisms of these associations remain unclear.

In the present research we will focus on the role of nutrition in the
relationship between depression and coeliac disease.

We will perform a case-control study in a large group of CD patients with and
without depression and who adhere strictly to a gluten-free diet, as well as
healthy individuals on a normal diet. We will investigate several nutritional
factors, and test the hypothesis that in some patients, the depressive symptoms
are related to low serotonergic function, caused by prolonged tryptophan
depletion induced by the gluten-free diet. Dietary intake will be assessed
using a food frequency questionnaire. We will also measure fasting plasma
tryptophan concentrations in this population along with a range of other
nutritional biomarkers that have previously been related to depression.
Participants will also be asked to complete self-report questionnaires related
to mood and health status and a structured psychiatric interview will be
performed.

The risks of participating in this study are limited, test-results can be
informative and even beneficial to participants. The burden of the study
consists of travelling to the test-location, being present for two hours, being
interviewed, filling out questionnaires and undergoing venapuncture.