[Mixed depression and DSM-5: A critical review]

Abstract

Background: Mixed depression is a depressive syndrome characterized by the presence, along with the typical depressive symptoms of depression, of those of over activation and excitation. If sometimes this activation is expressed by classical hypomanic symptoms, it is often observed by means of more subtle expression: inner tension, crowded thoughts, dramatic expression suffering, and unproductive agitation. It is important to identify mixed depression because such patients are particularly at risk of suicidal behaviors, substance abuse and therapeutic resistance. Even if therapeutic strategies continue to be discussed, treatments should rely on mood stabilizers and antipsychotics instead of antidepressants as in pure depression. Even though the concept of mixed depression has been described for more than twenty years, first by Koukopoulos and then by other authors, it had been little studied, especially because it did not appear in international psychiatric classifications. The DSM-IV supported a very narrow conception of the mixed states because the criteria required simultaneous full manic and full depressive syndromes, corresponding only to some dysphoric manias. The recently published DSM-5 proposes modifications in mood and bipolar disorder classifications, and especially introduces the possibility to specify depressive and manic episodes with "mixed features". To diagnose depression with mixed features, a full depressive syndrome has to be present together most of time with three hypomanic symptoms, except symptoms that are considered as overlapping (that can be observed either in mania or in depression), i.e. agitation, irritability and distractibility.

Methods: Critical analysis of DSM criteria and review of literature.

Results: We first analyzed the clinical relevance of the definition of depression with mixed features which could correspond to mixed depression. The problem is that the hypomanic symptoms allowed by the manual lead to symptom associations that are rather illogical (as euphoria with depression) or improbable (as increased or excessive involvement in activities that have a high potential for painful consequences). Also, some more specific symptoms that can be observed in mixed depression are not mentioned (such as hypersensitivity to light or noise, absence of motor retardation, dramatic expressivity of suffering). The DSM-5, as did DSM-IV, refers to an understanding of mixed depression as a simple addition of depressive and manic symptoms. The classification does not take into account that the symptoms could be rather different from hypomania, as the expression of an overactive thought in a depressed mind. Secondly, we reviewed cohort studies using the DSM-5 criteria (or similar criteria with the exclusion of overlapping symptoms), and as a consequence of the poorly defined symptoms, we found that the diagnosis of mixed depression according to DSM-5 is almost impossible, either in unipolar or in bipolar depression.

Conclusions: We think, with others, that the definition of the mixed depression by the DSM-5 is not clinically relevant and misses important information about the concept. Clinicians can be attentive to the identification of mixed character in depression, even if DSM-5 criteria are not fully met. Unfortunately, the DSM-5 definition could undermine research efforts for a better understanding of epidemiology, phenomenology and therapeutics of mixed depression. We propose and discuss alternative solutions for defining mixed depression, such as the absence of exclusion of "overlapping" symptoms, a more insighted phenomenology, or a dimensional approach.

Keywords: Bipolar disorder; Diagnostic; Mixed state; Nosologie; Nosology; Psychiatric diagnosis; Trouble bipolaire; État mixte.