Delayed mood transitions in major depressive disorder

The hypothesis defended here is that the process of mood-normalizing transitions fails in a significant proportion of patients suffering from major depressive disorder. Such a failure is largely unrelated to the psychological content. Evidence for the hypothesis is provided by the highly variable and unpredictable time-courses of the depressive episodes.

The main supporting observations are: (I) mood transitions within minutes or days have been reported during deep brain stimulation, naps after sleep deprivation and bipolar mood disorders; (2) sleep deprivation, electroconvulsive treatment and experimental drugs (e.g., ketamine) may facilitate mood transitions in major depressive disorder within hours or a few days; (3) epidemiological and clinical studies show that the time-to-recovery from major depressive disorder can be described with decay models implying very short depressive episodes; (4) lack of relationship between the length of depression and recovery episodes in recurrent depression; (5) mood fluctuations predict later therapeutic success in major depressive disorder. We discuss some recent models aimed to describe random mood transitions.

The observations together suggest that the mood transitions have a wide variety of apparently unrelated causes. We suggest that the mechanism of mood transition is compromised in major depressive disorder, which has to be recognized in diagnostic systems. (C) 2014 Elsevier Ltd. All rights reserved.