1 2 Original article 3 Mediating role of borderline personality traits in the effects of 4 childhood maltreatment on suicidal behaviour among mood disorder 5 patients 6 K.I. Aaltonen Q1 a,b,c , T. Rosenstro ¨m d , I. Baryshnikov a , B. Karpov a , T. Melartin a , 7 K. Suominen c , M. Heikkinen a , P. Na ¨a ¨ta ¨nen a , M. Koivisto a , G. Joffe a , E. Isometsa ¨ a, * 8 a Department Q2 of Psychiatry, University of Helsinki and Helsinki University Hospital, PO Box 22, 00014 Helsinki, Finland 9 b Department of Health, Mental Health Unit, National Institute of Health and Welfare, Helsinki, Finland 10 c Department of Social Services and Health Care, PO Box 6000, 00099 Helsinki, Finland 11 d Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki, PO Box 9, 00014 Helsinki, Finland 12 13 1. Introduction 14 Childhood experiences correlate with adult physical and mental 15 well-being [1,2]. The most adverse outcomes include associations 16 of childhood maltreatment (CM) with premature death [3] and 17 suicidal behaviour [4]. While research on suicide deaths remains 18 scarce [5], considerable evidence shows an association between 19 CM and suicidal ideation and attempts [4]. Although several 20 previous studies have examined this relationship by estimating the 21 effect of covariates in analyses, few studies have investigated 22 potential mediating mechanisms [6–10]. 23 Borderline personality disorder (BPD) ranks among the most 24 prevalent personality disorder comorbidities among mood disor- 25 der patients [11,12]. Subthreshold BPD traits are even more 26 common [13]. Within mood disorder samples, CM is associated 27 with comorbid BPD diagnosis [14] and traits [15]. Aetiology of BPD 28 is multifactorial, including both inherited vulnerabilities and 29 developmental factors [16]. Family and twin studies of BPD 30 demonstrate familial transmission and moderate heritability 31 [17]. Psychological theories of development of BPD remark CM 32 and dysfunctional parenting [18–20] as environmental factors. European Psychiatry xxx (2017) xxx–xxx A R T I C L E I N F O Article history: Received 22 December 2016 Received in revised form 23 March 2017 Accepted 23 March 2017 Available online xxx Keywords: Depressive disorder Bipolar disorder Borderline personality disorder Suicidal behaviour Childhood maltreatment A B S T R A C T Background: Substantial evidence supports an association between childhood maltreatment and suicidal behaviour. However, few studies have examined factors mediating this relationship among patients with unipolar or bipolar mood disorders. Methods: Depressive disorder and bipolar disorder (ICD-10-DCR) patients (n = 287) from the Helsinki University Psychiatric Consortium (HUPC) Study were surveyed on self-reported childhood experiences, current depressive symptoms, borderline personality disorder traits, and lifetime suicidal behaviour. Psychiatric records served to complement the information on suicide attempts. We examined by formal mediation analyses whether (1) the effect of childhood maltreatment on suicidal behaviour is mediated through borderline personality disorder traits and (2) the mediation effect differs between lifetime suicidal ideation and lifetime suicide attempts. Results: The impact of childhood maltreatment in multivariate models on either lifetime suicidal ideation or lifetime suicide attempts showed comparable total effects. In formal mediation analyses, borderline personality disorder traits mediated all of the total effect of childhood maltreatment on lifetime suicide attempts, but only one fifth of the total effect on lifetime suicidal ideation. The mediation effect was stronger for lifetime suicide attempts than for lifetime suicidal ideation (P = 0.002) and independent of current depressive symptoms. Conclusions: The mechanisms of the effect of childhood maltreatment on suicidal ideation versus suicide attempts may diverge among psychiatric patients with mood disorders. Borderline personality disorder traits may contribute to these mechanisms, although the influence appears considerably stronger for suicide attempts than for suicidal ideation.  C 2017 Elsevier Masson SAS. All rights reserved. * Corresponding author. Fax: +358 9 47163735. E-mail address: erkki.isometsa@hus.fi (E. Isometsa ¨). G Model EURPSY 3507 1–8 Please cite this article in press as: Aaltonen KI, et al. Mediating role of borderline personality traits in the effects of childhood maltreatment on suicidal behaviour among mood disorder patients. European Psychiatry (2017), http://dx.doi.org/10.1016/ j.eurpsy.2017.03.011 Contents lists available at ScienceDirect European Psychiatry jo u rn al h om epag e: h ttp ://ww w.eu ro p s y- jo ur n al.co m http://dx.doi.org/10.1016/j.eurpsy.2017.03.011 0924-9338/  C 2017 Elsevier Masson SAS. All rights reserved.