2019 Volume 10 Pages 10-17
Mixed depression refers to the co-existence of a major depressive episode (MDE) and sub-threshold manic/hypomanic symptoms. Mixed depression is a common clinical entity, occurring in approximately 50% and 30% of MDEs due to bipolar disorder (BD) and major depressive disorder (MDD), respectively. However, it remains underdiagnosed and very often misdiagnosed as simply "major depression," adjustment disorder, anxiety disorder, or borderline personality disorder. Mixed depression suggests a diagnosis of BD in patients experiencing an MDE, and is associated with future progression to BD, antidepressant-induced mania/hypomania, and a family history of BD in patients with MDD. Patients with mixed depression exhibit poor prognosis, experiencing more severe episodes of longer duration, less inter-episodic remission, higher recurrence rates, more rapid cycling, a higher rate of co-morbid substance use and anxiety disorders, and a higher risk of suicidality. Antidepressant use can exacerbate symptoms of agitation and irritability and induce newly-developed suicidality without improving depressive symptoms. Because treatment strategies differ for mixed and non-mixed states, it is important to screen all patients with depression for co-existing manic/hypomanic symptoms. In this report, the author briefly reviews the clinical presentation, diagnosis, and impact of mixed depression on the course of mood disorders and pharmacological treatment.