Are bipolar disorder and depression related?

Mood: They are related in that they are both mood disorders. In other words, both affect emotions or moods. Treatment, however, is different in terms of medication. Bipolar usually requires a mood stabilizer; whereas, depression is usually treated with an antidepressant. Some times an antidepressant is added to a mood stabilizer, but it's uncommon for bipolar to be treated solely with an antidepressan.

Bipolar & Dep.: The two can coexist. One type of bipolar is bipolar type 2 , another is cyclothymic disorder.

Yes: They are both affective disorders--in general bipolar disorder does better with mood stabilizers.

Bipolar : Depression can be thought of as one half of bipolar disorder, with the other half being mania.