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Does temperamental instability support a continuity between bipolar II disorder and major depressive disorder?
1Hecker Psychiatry Research Center, Forli, Italy. francobenazzi@fbenazzi.it
Summary
This study found no bimodal distribution for cyclothymic temperament (CT) and borderline personality disorder (BPD) items between bipolar II (BP-II) disorder and major depressive disorder (MDD). This suggests a continuity between BP-II and MDD, challenging current diagnostic categories.
Area of Science:
- Psychiatry
- Mood Disorders
- Personality Disorders
Background:
- Current diagnostic categories for mood disorders, specifically bipolar and depressive disorders, are being questioned.
- Cyclothymic temperament (CT) and borderline personality disorder (BPD) traits are more prevalent in bipolar II (BP-II) disorder than in major depressive disorder (MDD).
- Historical views, like Kraepelin's, considered temperamental instability foundational to a unitary concept of mood disorders.
Purpose of the Study:
- To assess the distribution of CT and BPD items in patients diagnosed with BP-II and MDD.
- To determine if the absence of a bimodal distribution (a "zone of rarity") for these items supports a continuum between BP-II and MDD.
Main Methods:
- A consecutive sample of 138 BP-II and 71 MDD outpatients were assessed in a private psychiatric practice.
- Diagnosis of BP-II and MDD was confirmed using the Structured Clinical Interview for DSM-IV Axis I Disorders-Clinician Version (SCID-CV).
- Patients self-assessed for CT using the TEMPS-A and for borderline personality traits (BPT) using the SCID-II Personality Questionnaire; Kernel density estimation analyzed item distributions.
Main Results:
- CT and BPT items were found to be significantly more common in patients with BP-II compared to those with MDD.
- Kernel density estimates revealed a normal-like, non-bimodal distribution for both CT and BPT items across the entire sample.
- No "zone of rarity" was observed in the distribution of these personality and temperament items.
Conclusions:
- The absence of bimodality in CT and BPT item distributions suggests a continuity between BP-II disorder and MDD.
- These findings challenge the current categorical distinctions between BP-II and MDD based on traditional diagnostic validators.
- The results support a dimensional view of mood disorders, aligning with historical perspectives on temperamental instability.
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