Presence and Overlap of Bipolar Symptoms and Borderline Features during Major Depressive Episodes

Bipolar symptoms and borderline personality features occur in both unipolar and bipolar major depressive episodes (MDEs). We investigated their prevalence, severity, co-occurrence and overlap.

We interviewed 124 psychiatric outpatients with MDE using the Structured Clinical Interview for DSM-IV-TR Axis I and II Disorders, the Borderline Personality Disorder Severity Index (BPDSI-IV), and about past (hypo)manic episodes, and stratified them according to the principal diagnosis into subcohorts of major depressive disorder (MDD, n = 50), bipolar disorder (BD, n = 43), and borderline personality disorder (BPD, n = 31). We quantified (hypo)manic symptoms using a novel semi-structured interview (MIXed symptoms during MDE, MIX-MDE) with good psychometric qualities.

The subcohorts did not differ in MDE severity. They differed significantly in some (hypo)manic symptoms being present on most days in 24% of MDD, 30% of BD, and 42% of BPD subcohort, but only 5% of the BD subcohort fulfilled the DSM-5 mixed features. The mean MIX-MDE scores were 5.7 (SD 4.0), 12.0 (8.2) and 10.5 (7.5), and BPDSI-IV scores 15.6 (7.0), 17.2 (6.2) and 26.9 (8.7), respectively (both p < 0.001). (Hypo)manic days and unspecific symptoms of distractibility and irritability inflated the correlation of observed (hypo)manic symptoms and borderline features.

Moderate sample size, limited age variation (18-50 years); no previous validation of MIX-MDE.

Presence of some mixed and borderline features is common in MDEs, with overlap and diagnosis-specific differences. Unspecific symptoms of irritability and distractibility and the aggravating impact of hypomania on perceived BPD features blur the differential diagnosis.