In recent writing it's usually seen as more clear to treat them as distinct (though related) disorders rather than bipolar being a subset of depression, althoug

In recent writing it's usually seen as more clear to treat them as distinct (though related) disorders rather than bipolar being a subset of depression, although that usage is still common. The ICD, for example, classifies "Bipolar affective disorder" (F31) and "Recurrent depressive disorder" (F33) as two distinct disorders under the parent category "Mood [affective] disorders".