Associations between borderline personality disorder symptomatology and major depressive disorder: Insights from a...

Understanding factors influencing the onset and course of major depressive disorder (MDD) is critical due to its frequently unfavorable prognosis. While Borderline Personality Disorder (BPD) seems to negatively affect the course of MDD, the role of subthreshold BPD symptoms remains unclear. This study investigated the impact of subthreshold BPD symptoms on the onset and persistence of MDD over a three-year follow-up in a general population sample of 4618 participants from the Netherlands Mental Health Survey and Incidence Study. MDD was assessed using the Composite International Diagnostic Interview 3.0 and BPD symptoms via the International Personality Examination. Logistic regression models were used. Respondents with 1-2 BPD symptoms (OR = 2.36, 95% CI = 1.56-3.56) and 3-4 BPD symptoms (OR = 4.36, 95% CI = 2.22-8.58) had significantly higher odds of developing MDD compared to those without BPD symptoms. These results remained robust after adjustment for potential confounders. Sensitivity analyses indicated BPD symptoms were linked to increased risk for both first onset and recurrence of MDD, with a seemingly stronger effect on recurrence. BPD symptoms were not significantly associated with MDD persistence, but limited power may have influenced this result. A significant dose-response relationship was observed for onset and recurrence, but not persistence. These findings suggest individuals with subthreshold BPD symptoms have elevated risk for new and recurrent depressive episodes, while no consistent association was observed with persistence of depression. Targeting BPD symptoms in (relapse) prevention may improve MDD outcomes.