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16-05-2011 | Immunology | Article

Allergy linked to suicide risk

Abstract

Free abstract

MedWire News: Results from a Danish study suggest that individuals who have received inpatient treatment for allergy are at increased risk for suicide.

"Recent evidence has shown that the seasonality of suicide tends to co-occur with seasonal aeroallergens that dramatically peak in spring (ie, tree-pollen) and in late summer/early fall (ie, ragweed), and that such a co-occurrence is more prominent for suicide victims with a history of mood disorders," explain Ping Qin (Aarhus University) and team.

"However, no study, to our awareness, has used individual-level data from a large-scale population to systematically address the effect of allergy on risk for subsequent suicide completion, while taking into account personal history of mood disorder and other risk factors," they add.

The researchers therefore studied data on 27,096 individuals who committed suicide between 1981 and 2006 and 467,571 controls from the general population who were matched for date of birth, gender, and time of suicide (20 controls per case).

They used the Danish General Hospital Registry to identify all individuals who had hospital treatment for allergic illness as a primary diagnosis. The Danish Psychiatric Central Registry was also examined to identify all those who had received treatment for mood disorders.

The researchers found that 1.17% of suicide victims had previously received hospital treatment for allergies compared with 0.79% of matched controls. The most common diagnosis was allergic rhinitis with bronchial asthma, followed by allergic rhinitis without asthma, and atopic dermatitis.

Overall, a history of inpatient treatment for allergy predicted suicide completion, with an incidence rate ratio (IRR) of 1.46. However, outpatient allergy treatment did not predict suicide completion.

The increased risk for suicide completion associated with an inpatient history of allergy fell slightly after adjustment for mood disorders and other psychiatric diagnoses (adjusted IRR=1.37), and after further adjustment for marital status, income, citizenship, and place of residence (IRR=1.31), but remained significant.

Further examination of the relationship between a history of allergy and mood disorder on suicide risk showed that the two conditions act at the same time to confer a lower risk for suicide than would be expected based on the additive independent effects of the two exposures. Indeed, allergy increased suicide risk only in individuals with no history of mood disorder, whereas it eliminated suicide risk in those with such a history.

Qin and team conclude in the journal Allergy: "Although we should not alert the need of assessment for suicidality of all patients with allergy, the results suggest that physicians treating patients with allergic disorders should be vigilant about expressions of suicidal ideation or signs of self-harm, particularly for those with a recent diagnosis or severe allergy."

MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

By Mark Cowen

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