What percent of individuals who has been diagnosed with a major depressive disorder will also develop bipolar disorder?

There is no evidence to suggest that individuals who have been diagnosed with major depressive disorder (MDD) will develop bipolar disorder. However, MDD and bipolar disorder are both considered mood disorders and may share some similar symptoms. It is possible for someone to experience both MDD and bipolar disorder at different times in their life, but it is incorrect to assume that MDD necessarily leads to bipolar disorder.