Joel Yager, MD reviewing Perich T et al. Acta Psychiatr Scand 2016 Jun 20.

A sophisticated statistical analysis of depressive episodes in bipolar I and bipolar II patients reveals several possible subtypes distinguished by key clinical features.

Distinguishing bipolar depression from unipolar depression is of considerable clinical value. Might further subtyping of bipolar depressive episodes yield additional benefits? To find out, Australian investigators used latent class analysis, a statistical technique searching large numbers of variables for underlying clusters of phenomena. Data on 243 depressed patients with bipolar I or bipolar II disorder were analyzed (mean age, 39; 62% women).

Two robust solutions emerged, one suggesting three distinct classes (subtypes) and the other suggesting two. No meaningful differences distinguished bipolar type 1 from type 2. In the three-subtype solution, possible characteristics were identified as:

• Subtype 1 (28.9% of patients): hypersomnia, increased appetite/weight gain, suicidal ideation, evening worsening, and a family history of depression.
• Subtype 2 (44.3%): anxiety, insomnia, irritability, psychomotor retardation, guilt, worthlessness, evening worsening, and suicidal ideation.
• Subtype 3 (26.8%): earlier onset of first depressive and hypomanic/manic episodes, indecisiveness, and reduced weight loss.

Subtype-1 patients were more likely to have been prescribed lamotrigine and subtype-2 patients were more likely to be impaired (i.e., using government assistance).

In the two-class solution, subtype 1 (73.5%) was characterized by weight loss and early onset, and subtype 2 (26.5%) by hypersomnia, greater appetite/weight gain, and psychomotor agitation.

CITATION(S):

Perich T et al. Are there subtypes of bipolar depression? Acta Psychiatr Scand 2016 Jun 20; [e-pub]. 

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