Mood patterns and classification in bipolar disorder.

Objective: The aim of this review is to highlight recent studies that have questioned the current split of mood disorders into the categories of bipolar and depressive disorders.

Results: A continuity between bipolar disorders (mainly bipolar II disorder) and major depressive disorder was supported by several lines of evidence: depressive mixed states (mixed depression) and dysphoric (mixed) hypomania (opposite polarity symptoms in the same episode do not support the splitting between mania/hypomania and depression); family history, major depressive disorder is the most common mood disorder in relatives of bipolar probands; lack of points of rarity between the depressive syndromes of bipolar II disorder and major depressive disorder; bipolar features in major depressive disorder; major depressive disorder shifting to bipolar disorders; history of manic/hypomanic symptoms in major depressive disorder and correlation between lifetime manic/hypomanic symptoms and depressive symptoms in major depressive disorder; factors of hypomania inside major depressive disorder; recurrent course of major depressive disorder; depression more common than mania and hypomania in bipolar disorders; trait mood lability in major depressive disorder.

Conclusions: This review of the recent findings on the relationship between bipolar disorders (especially bipolar II disorder) and depressive disorders seems to support a continuity among mood disorders, and runs against the current classification of mood disorders dividing them into independent categories. Further research is needed in the area, in part because of its possible treatment impact.