Borderline personality disorder and depression severity predict suicidal outcomes: A six‐month prospective cohort study of depression, bipolar depression, and borderline personality disorder

Background Suicide risk is high in patients with major depressive disorder (MDD), bipolar disorder (BD) and borderline personality disorder (BPD). Whether risk levels of and risk factors for suicidal ideation (SI) and suicide attempts (SA) are similar or different in these disorders remains unclear, as few directly comparative studies exist. The relationship of short‐term changes in depression severity and SI is underinvestigated, and might differ across groups, for example, between BPD and non‐BPD patients. Methods We followed, for 6 months, a cohort of treatment‐seeking, major depressive episode (MDE) patients in psychiatric care (original n = 124), stratified into MDE/MDD, MDE/BD and MDE/BPD subcohorts. We examined risks of suicide‐related outcomes and their risk factors prospectively. We examined the covariation of SI and depression over time with biweekly online modified Patient Health Questionnaire 9 surveys and analysed this relationship through multi‐level modelling. Results Risk of SA in BPD (22.2%) was higher than non‐BPD (4.23%) patients. In regression models, BPD severity was correlated with risk of SA and clinically significant SI. During follow‐up, mean depression severity and changes in depression symptoms were associated with SI risk regardless of diagnosis. Conclusions Concurrent BPD in depression seems predictive for high risk of SA. Severity of BPD features is relevant for assessing risk of SA and SI in MDE. Changes in depressive symptoms indicate concurrent changes in risk of SI. BPD status at intake can index risk for future SA, whereas depressive symptoms appear a useful continuously monitored risk index.