A comparison of the phenomenology and illness course of major depressive episodes in major depressive disorder and bipolar I and bipolar II disorders

  • Professor Philip Mitchell, University of New South Wales, Australia
  • Mr Andrew Frankland, University of New South Wales, Australia
  • Mr Dusan Hadzi-Pavlovic, University of New South Wales, Australia
  • Dr Gloria Roberts, University of New South Wales, Australia
  • Mr Adam Wright, University of New South Wales, Australia
  • A/Professor Colleen Loo, University of New South Wales, Australia
  • Professor Gin Malhi, University of Sydney, Australia
  • Professor Michael Breakspear, Queensland Institute of Medical Research, Australia

Objectives: To compare the phenomenology of major depressive episodes in subjects with bipolar and major depressive disorders.

Methods: A total of 143 participants with DSM-IV unipolar depression and 415 patients with DSM-IV bipolar disorder (351 with bipolar I disorder and 64 with bipolar II disorder) from a genetic study and specialized clinic samples were assessed using the Diagnostic Interview for Genetic Studies. Across diagnostic groups, we compared illness course measures as well as symptomatology and mental state signs during the most severe lifetime depressive episode.

Results: Both bipolar I and bipolar II participants reported a greater number of lifetime depressive episodes compared to unipolar participants. Symptomatology differed across diagnostic groups, with a greater proportion of both bipolar I and bipolar II participants reporting pathological guilt, difficulty concentrating, recurrent suicidal ideation and diurnal variation during their most severe depressive episode. Compared to unipolar participants, bipolar I participants were more likely to report hypersomnia, psychomotor retardation, self-harm and psychotic features while psychomotor agitation was more common among bipolar II participants.

Conclusions: There were significant differences in the symptom profile characterizing depressive episodes. Many of the findings replicate distinctions between major depressive disorder and bipolar depression which we have previously reported from other samples. This suggests distinct phenomenological differences in depression between unipolar and bipolar patients, with implications for both clinical practice and the nosological and biological distinctions between the two disorders.