A continuity between bipolar II depression and major depressive disorder?

Area of Science:

• Psychiatry
• Mood Disorders Research
• Clinical Psychology

Background:

• Recent studies question the categorical division of mood disorders into bipolar and depressive types.
• Mixed states, particularly mixed depression, may indicate a continuum between bipolar II (BP-II) depression and major depressive disorder (MDD).

Purpose of the Study:

• To evaluate the distribution of intradepressive hypomanic symptoms in BP-II and MDD depressions.
• To determine if a bimodal distribution supports categorical distinction or if a lack of bimodality suggests continuity between BP-II and MDD.

Main Methods:

• Interviewed 389 BP-II and 261 MDD outpatients using the Structured Clinical Interview for DSM-IV and Hypomania Interview Guide (HIG).
• Assessed intradepressive hypomanic symptoms and defined mixed depression as MDE plus 3 or more hypomanic symptoms.
• Analyzed symptom distribution using Kernel density estimation and histograms.

Main Results:

• BP-II depression showed earlier onset, higher likelihood of atypical and mixed features, more recurrences, and greater bipolar family history loading compared to MDD.
• BP-II depression had significantly more irritability, racing thoughts, distractibility, psychomotor agitation, talkativeness, goal-directed activity, and risky behaviors.
• The overall distribution of intradepressive hypomanic symptoms lacked bimodality.

Conclusions:

• Diagnostic validators like family history and age at onset suggest BP-II and MDD are distinct.
• The 'bimodality' approach to symptom distribution implies a continuity between BP-II and MDD.
• The optimal classification method for mood disorders remains undetermined.