Adults with clinically significant borderline personality disorder traits (BPTs) are at high risk of experiencing suicidal thoughts and behaviors (STBs). STBs among those with BPTs have been associated with suicidal beliefs (e.g., that one is unlovable or that distress is intolerable). However, the extent to which suicidal beliefs uniquely mediate the relationship between emotional distress and STBs among individuals with BPTs is not known. Individuals admitted to an inpatient unit (N = 198) with recent STBs completed assessments of BPTs, depression, suicidal beliefs, suicidal ideation, and suicide attempt history. Moderated mediation models were used to explore whether suicidal beliefs mediated the relationship between depression and STBs conditional on BPTs. Suicidal patients with versus without BPTs reported stronger suicidal beliefs and more severe STBs (i.e., suicidal ideation, lifetime attempts). Exploratory moderated mediation analysis demonstrated that suicidal beliefs mediated the relationship between depression and suicidal ideation as well as suicide attempts. The mediation effect of suicidal beliefs on the depression-ideation and depression-attempt relationship was not significantly moderated by BPTs. This study was cross-sectional and therefore the estimated mediation models must be considered exploratory. Longitudinal research will be needed to assess the potential causal mediation of suicidal beliefs on the relationship between depression and STBs. The results of this study suggest that suicidal beliefs may play a significant role in the relationship between depression and STBs for inpatients with a history of suicidality regardless of BPTs. This suggests suicidal beliefs may be an important treatment target for adults with a history of STBs.
Keywords: Borderline personality disorder; inpatient; moderation.