Sunday 06 December 2009, 18:51

Allergy and major depression

The association between allergies and depressive disorders

Allergy and major depression

A recent study conducted at the University of Calgary (Canada) has demonstrated that major depression is associated with an increased risk of developing non-food related allergies, although the inverse relationship still needs to be confirmed.


A relationship between allergy and depression has been suspected for many years. Various epidemiological cross-sectional studies have shown a correspondence between the prevalence of allergies and the incidence of depressive disorders and various hypothesis have been proposed to explain the observed epidemiological depression-allergy association. 


Theoretically it is plausible that allergy may increase depression risk, as well as it is plausible that depression may increase allergy risk. For example the brain might interpret the immune activation involved in allergy as a stressor and, consequently, trigger a stress response that might include depression. On the other hand, depressive disorders are associated with increased levels of pro-inflammatory cytokines (IL-1, IL-6, TNF-alpha, IFN-alpha) that, in turn, might contribute to the pathogenesis of some types of allergies.


However cross-sectional studies cannot distinguish between these two possibilities. The study conducted by Canadian researchers has been the first to employ a longitudinal design which, unlike cross-sectional studies, is addressed to investigate the direction of the relationship between allergy and major depression. Well, based on their observations, the researchers concluded the following: depression and food allergies have no association with each other; major depression has an effect on the risk of developing non-food related allergies, but the inverse relationship remains unknown.


The mechanism by which depression increases the risk of allergy remains speculative. Is it due to shared genetic factors or is it to be considered as an effect of immunological changes occurring during depression? The question still remains open and requires clarification by further study.


By Chiara De Carli

Category: Allergy

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