Allergies and Mental Illness

According the 1966 Finnish birth cohort Published in Molecular Psychiatry 2003 8 , several lines of evidence suggest that there exists an association between depression and atopic allergies (ie, asthma, atopic eczema and allergic rhinitis).1–4 An excess of IgE-mediated allergies has been found in patients with depression, and conversely, increased amounts of depressive symptoms have been reported in patients suffering from atopic disorders (P. 738).

A 2002 Canadian Community Health Study published in the Int'l. j. psychiatry in medicine, is the first to confirm the presence of an association between allergies and mood and anxiety disorders, as opposed to symptom ratings, in a general population sample( P. 11). An association between allergies and mood disorders has been suspected for many years. Only a few epidemiological studies have examined associations between allergies and psychiatric symptoms in non-clinical populations. Subjects reporting three or more atopic disorders were found to have an elevated probability of exceeding a threshold score on the depressive symptom scale. The results of several statistical models were interpreted as providing support for shared familial vulnerability between allergies and depressive symptoms. In a 1966 Finnish birth cohort in an investigation that included skin tests to three common allergens, several questions about depression and two depression rating scales. Compared to women with negative skin tests, women with positive skin tests were slightly more likely to report that they had been diagnosed with depression by a doctor, 6.9% versus 4.3%; no difference was found in men. A subsequent report cast some doubt on whether this association was unique to women. When depressive symptom ratings were incorporated into the definition of depression, a significant association was observed in men with high symptom levels.

These reports have stimulated considerable interest in pathophysiological connections between depression and immune functioning. Various potential explanations for the association have been put forward, mostly involving cytokine-related mechanisms. There is a higher frequency of major depression, panic disorder and social phobia in women, no significant difference for bipolar disorder, and a higher prevalence of substance dependence in men. The same pattern of association with allergies is seen in men and women and in the younger and older age groups: there is a consistently higher prevalence in subjects reporting allergies, except for substance use disorders (P.14 &17). For social phobia, the 95% confidence intervals for the prevalence estimates in respondents with and without allergies overlap across a part of their range, indicating that both prevalence estimates are consistent with some similar population prevalence values (P.17). These descriptive findings make a contribution to the literature in several ways. First, they provide the first population-based confirmation of an association between depressive disorders, diagnosed using a fully structured research diagnostic interview, and self-reported allergies. All previous studies have used brief instruments or else, as in the case of the Finnish studies, symptom rating scales. Second, whereas the literature has tended to focus almost exclusively on the issue of depression, these results clearly show that both anxiety disorders and mood disorders (and within this category both major depressive disorder and bipolar disorder) are associated with self-reported allergies (P.20).

Previous literature suggests that the association between allergies and mood symptoms may be stronger in men than in women. No gender by allergy interactions were found in this analysis, so this possibility was not confirmed (P. 20).

In a Psychological Bulletin on Allergy and depression (1993) Paul S. Marshall writes; Practicing allergists' reports of allergic responses causing depression symptomatology have been and continue to be very controversial. There is some debate that there is an increased incidence of depression in allergic individuals. (P.21)

There is a great deal of evidence that the neuroanatomical structures innervated by cholinergic trnsmission play a critical role in the major behavioral symptoms of depression: mood changes, increased neuroendocrine activity, including higher levels of circulating corticosteroids, altered REM sleep cycles, and change in psychomotor activity (retardation or agitation).

Cholinergic neurotransmission occurs in several regions of the brain, including the hippocampus, amygdala, and lateral hypothalamus, which have a significant impact on mood (P. 13).

Not only do the CNS cholinergic agonists produce depressive symptomatology, but affective disorder patients are much more sensitive to these agents than normal subjects or patients with other psychiatric disorders. Affective disorder patient exhibited a