Allergy: A risk factor for suicide?

Abstract

The rates of depression, anxiety, and sleep disturbance (suicide risk factors) are greater in patients with allergic rhinitis than in the general population. The rate of allergy is also greater in patients with depression. Preliminary data suggest that patients with a history of allergy may have an increased rate of suicide. Clinicians should actively inquire to diagnose allergy in patients with depression and depression in patients with allergy.Spring peaks of suicide are highly replicated, but their origin is poorly understood. Preliminary epidemiologic data suggest that seasonal spring peaks in aeroallergens are associated with seasonal spring peaks in suicide. Our research in Brown Norway rats demonstrates that sensitization and exposure to aeroallergens induces anxiety-like and aggressive behaviors as well as allergy-related helper T-cell type 2 (Th2) cytokine gene expression in the prefrontal cortex. Thus, it is possible that sensitization and exposure to aeroallergens, which peak in spring, may be conducive to seasonal exacerbation of suicide risk factors such as anxiety, depression, hostility/ aggression, and sleep disturbance. Connecting allergy with suicide and suicide risk factors adds to previous neurologic literature connecting allergy with migraines and seizure disorders.Our recent report of Th2 (allergy-mediating) cytokine expression in the orbito-frontal cortex of suicide victims should lead to future studies to test the hypothesis that mediators of allergic inflammation in the nasal cavities may result in Th2 cytokine expression in the brain, influencing affect and behavioral modulation.Certain medications used to treat allergy can exacerbate suicide risk factors, potentially worsening suicide risk and even triggering suicide. Systemic (but not topical) corticosteroids have been associated with manic and depressive episodes and mixed mood states. Recently, the US Food and Drug Administration started investigating the possibility that montelukast may trigger suicide. Although this association requires further exploration and confirmation, clinicians should err on the side of caution, inquiring about past suicide attempts; hopelessness; reasons for living; and suicidal ideation, intent, or plan; and referring the patient to a mental health professional for evaluation if appropriate. One of the most dramatic environmental changes, which coincides with physical symptoms, is the robust increase in pollen during the spring and the corresponding increased incidence of upper respiratory inflammation. Pollen is the most important and the most seasonal of the aeroallergens [3, Class III]. Every year, the air is flooded with pollen from wind-pollinated plants, and the development of allergies due to human exposure is an unfortunate consequence of this process. Tree pollination occurs in the spring and represents the largest source of airborne pollen (∼ 75% of the yearly total). As an example of the time window of pollen peaks, we refer to the weekly mean values reported for total pollen production in the B...

Mood-worsening with high-pollen-counts and seasonality: A preliminary report

“…However, our current study adds a somewhat greater degree of temporal specificity in that our analysis indicates that mood sensitivity to tree pollen specifically predicts non-winter SAD and not winter SAD. The results are also consistent with the reported association between allergy and depression (Bell et al, 1991;Hashiro and Okumura, 1998;Marshall et al, 2002;Postolache et al, 2005b;Timonen et al, 2001;Timonen et al, 2003a;Timonen et al, 2003b;Timonen et al, 2002;). The potential relevance of the association between allergy and depression is highlighted by the very high (>50%) prevalence of a positive skin reaction to allergens in the general population (Arbes et al, 2005).…”

“…Based on the temporal coincidence between seasonal peaks in tree pollen and peaks of suicide, we have hypothesize that seasonality of suicide could be driven by a combination of environmental triggers and vulnerability, i.e. seasonal aeroallergens and a triple vulnerability for allergy, depression, and suicide (Postolache et al, 2005b). Using a large scale epidemiological approach, we have preliminarily reported an association between windows of high tree pollen and higher suicide rates (Postolache et al, 2005a).…”

“…The mechanisms that might explain the association between allergy and depression, in general, and suicide, specifically, are poorly understood. A number of potential underlying processes have been considered and are under investigation (Postolache et al 2005b). …”

An important social problem: allergic rhinitis

“…[14] Previous reports indicate that AR was associated with anxiety symptoms, depressive syndromes and even with suicide. [15] However this relationship is difficult to prove. The relationship between AR and mood/anxiety disorders might be explained with several suggestions.…”

“…[19] Although not proved, the association between allergen exposure and cerebral dysfunction (if any) should be investigated. [15] …”