Research report Psychiatric comorbidity may not predict suicide during and after hospitalization. A nested case–control study with blinded raters Fredrik A. Walby ⁎ , Erik Odegaard, Lars Mehlum Suicide Research and Prevention Unit, Institute of Psychiatry, University of Oslo, Sognsvannsveien 21, building 12. N-0320 Oslo, Norway Received 14 November 2005; received in revised form 31 January 2006; accepted 1 February 2006 Available online 20 March 2006 Abstract Background: To investigate the differential impact of DSM-IV axis-I and axis-II disorders on completed suicide and to study if psychiatric comorbidity increases the risk of suicide in currently and previously hospitalized psychiatric patients. Methods: A nested case–control design based on case notes from 136 suicides and 166 matched controls. All cases and controls were rediagnosed using the SCID-CV for axis-I and the DSM-IV criteria for axis-II disorders and the inter-rater reliability was satisfactory. Raters were blind to the case and control status and the original hospital diagnoses. Results: Depressive disorders and bipolar disorders were associated with an increased risk of suicide. No such effect was found for comorbidity between axis-I disorders and for comorbidity between axis-I and axis-II disorders. Limitations: Psychiatric diagnoses, although made using a structured and criteria-based approach, was based on information recorded in case notes. Axis-II comorbidity could only be investigated at an aggregated level. Conclusions: Psychiatric comorbidity did not predict suicide in this sample. Mood disorders did, however, increase the risk significantly independent of history of previous suicide attempts. Both findings can inform identification and treatment of patients at high risk for completed suicide. © 2006 Elsevier B.V. All rights reserved. Keywords: Suicide; Mental disorders; Comorbidity; Diagnosis; Inpatients; Outpatients 1. Introduction A history of inpatient psychiatric treatment is among the strongest known predictors of suicide, with a population attributable risk of about 40% (Qin et al., 2003). Still, the majority of people having been previously hospitalized for severe mental disorders do not die from suicide. Many studies (Black and Winokur, 1986; Dumais et al., 2005; Geddes and Juszczak, 1995; Geddes et al., 1997; Goldacre et al., 1993; Harris and Barraclough, 1997; Ho, 2003; Mortensen et al., 2000; Pokorny, 1983; Powell et al., 2000) have reported on suicide risk factors associated with different psychiatric disorders in former or current inpatients. Most studies find that the risk of suicide in this population is highest in patients with mood disorders, and points to the post- discharge period as the time of greatest risk. There are, however, several methodological limitations to this research. Nearly all studies in this field are based on clinical diagnoses from large case registries. All but one study (Powell et al., 2000) use diagnoses made according to ICD 8th or 9th revisions or DSM-II. Diagnostic data have almost invariably been collected through routinely clinical procedures, not through structured procedures. When made according to previous systems like the ICD- Journal of Affective Disorders 92 (2006) 253 – 260 www.elsevier.com/locate/jad ⁎ Corresponding author. Tel.: +47 913 45 195; fax: +47 22 92 39 58. E-mail address: fredrik.walby@medisin.uio.no (F.A. Walby). 0165-0327/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2006.02.005