Mixed states in bipolar disorder have been neglected, and the data concerning treatment of these conditions have been relatively obscure. To address this, we systematically reviewed published pharmacological treatment data for “mixed states/episodes” in mood disorders, including “with mixed features” in DSM–5. We searched PubMed, MEDLINE, The Cochrane Library, clinicaltrials.gov, and controlled-trials.com (with different combinations of the following keywords: “mixed states/features,” “bipolar,” “depressive symptoms/bipolar depression,” “manic symptoms,” “treatment,” “DSM–5”) through to October 2016. We applied a quality-of-evidence approach: first-degree evidence=randomized placebo-controlled studies of pharmacological interventions used as monotherapy; second-degree evidence=a similar design in the absence of a placebo or of a combination therapy as a comparative group; third-degree evidence=case reports, case series, and reviews of published studies. We found very few primary double-blind, placebo-controlled studies on the treatment of mixed states: the preponderance of available data derives from subgroup analysis performed on studies that originally involved manic patients. Future research should study the effects of treatments in mixed states defined using current criteria.

During the past two decades, a number of studies have found that depressed patients frequently have manic symptoms intermixed with depressive symptoms. While the frequency of mixed syndromes are more common in bipolar than in unipolar depressives, mixed states are also common in patients with major depressive disorder. The admixture of symptoms may be evident when depressed patients present for treatment, or they may emerge during ongoing treatment. In some patients, treatment with antidepressant medication might precipitate the emergence of mixed states. It would therefore be useful to systematically inquire into the presence of manic/hypomanic symptoms in depressed patients. We can anticipate that increased attention will likely be given to mixed depression because of changes in the DSM–5. In the present article, I review instruments that have been utilized to assess the presence and severity of manic symptoms and therefore could be potentially used to identify the DSM–5 mixed-features specifier in depressed patients and to evaluate the course and outcome of treatment. In choosing which measure to use, clinicians and researchers should consider whether the measure assesses both depression and mania/hypomania, assesses all or only some of the DSM–5 criteria for the mixed-features specifier, or assesses manic/hypomanic symptoms that are not part of the DSM–5 definition. Feasibility, more so than reliability and validity, will likely determine whether these measures are incorporated into routine clinical practice.

Mixed affective states, defined as the coexistence of depressive and manic symptoms, are complex presentations of manic-depressive illness that represent a challenge for clinicians at the levels of diagnosis, classification, and pharmacological treatment. The evidence shows that patients with bipolar disorder who have manic/hypomanic or depressive episodes with mixed features tend to have a more severe form of bipolar disorder along with a worse course of illness and higher rates of comorbid conditions than those with non-mixed presentations. In the updated Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM–5), the definition of “mixed episode” has been removed, and subthreshold nonoverlapping symptoms of the opposite pole are captured using a “with mixed features” specifier applied to manic, hypomanic, and major depressive episodes. However, the list of symptoms proposed in the DSM–5 specifier has been widely criticized, because it includes typical manic symptoms (such as elevated mood and grandiosity) that are rare among patients with mixed depression, while excluding symptoms (such as irritability, psychomotor agitation, and distractibility) that are frequently reported in these patients. With the new classification, mixed depressive episodes are three times more common in bipolar II compared with unipolar depression, which partly contributes to the increased risk of suicide observed in bipolar depression compared to unipolar depression. Therefore, a specific diagnostic category would imply an increased diagnostic sensitivity, would help to foster early identification of symptoms and ensure specific treatment, as well as play a role in suicide prevention in this population.