title: Allergy is associated with suicide completion with a possible mediating role of mood disorder - a population-based study.
abstract: BACKGROUND
  With increasing research suggesting a role of allergy on suicidality, this study, on a population level, delved into how allergy affects risk for suicide completion in the context of mood disorder and other factors.
  
  
  METHODS
  Based on the entire population of Denmark, we included 27,096 completed suicides and 467,571 live controls matched on sex and age with a nested case-control design. We retrieved personal information on hospital contacts for allergy and other variables from various Danish longitudinal registries and analyzed the data with conditional logistic regression.
  
  
  RESULTS
  We noted that 1.17% suicide victims, compared with 0.79% matched controls, had a history of hospital contact for allergy and that a history of allergy predicted an increased risk for suicide completion; however, the effect was confined to allergy that led to inpatient treatment (IRR: 1.59, 95% CI: 1.41-1.80). The increased risk was attenuated somewhat but remained significant when adjusted for personal psychiatric history and socioeconomic status. Meanwhile, we observed a nonsignificantly stronger effect in women than in men, and a significant age difference with a stronger effect for individuals at high ages. Moreover, we detected a significant interaction between allergy and mood disorder - even an antagonism effect of the two exposures. Allergy increased suicide risk only in persons with no history of mood disorder, whereas it eliminated suicide risk in those with a history of mood disorder.
  
  
  CONCLUSIONS
  The findings support a link between allergy and suicidality, with a possible mediating role of mood disorder.
authors.affiliation: National Centre for Register-based Research, Aarhus University, Aarhus, Denmark. pq@ncrr.dk
authors.forename: P
authors.initials: P
authors.lastname: Qin
authors.forename: P B
authors.initials: PB
authors.lastname: Mortensen
authors.forename: B L
authors.initials: BL
authors.lastname: Waltoft
authors.forename: T T
authors.initials: TT
authors.lastname: Postolache
mesh_terms: D000367:Age Factors; D016022:Case-Control Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006760:Hospitalization; D006801:Humans; D006967:Hypersensitivity / Q000523:psychology*; D007297:Inpatients; D008297:Male; D019964:Mood Disorders / Q000523:psychology*; D012307:Risk Factors; D012737:Sex Factors; D012923:Social Class; D013405:Suicide