Restoration of positive mood, in addition to reducing negative mood, is an important treatment goal in the management of depression. The need to restore positive mood states in depressed patients is not adequately addressed by available treatments for major depressive disorder (MDD), suggesting that this mood dimension could be a useful target for drug development. However, for positive mood restoration to become a valid target for antidepressant drug development certain questions should be answered: are symptoms of decreased positive mood phenomenologically distinct from other symptoms of MDD? Should they be considered a distinct aspect of MDD in the diagnostic nomenclature? Is there evidence for differential responsiveness to treatment? Is the underlying pathophysiology understood and different from that of other MDD symptoms? Is low positive mood specific to depression or does it contribute to psychopathology in other disorders? Beyond these basic questions, this review identifies a number of design issues that need to be considered when conducting studies that target improving positive mood. These design issues include (1) what population to study, (2) what line of treatment to target, (3) the appropriateness and validation of methods and measures to evaluate positive mood and its restoration, (4) the role of functional outcome measures in determining success of the treatment, and (5) optimal designs for add-on therapy versus monotherapy agents.
Keywords: Depression; drug development; phenomenology; positive mood; reward circuits; symptom dimension.
© The Author(s) 2014.