ABSTRACT
Depressed mood represents something of a conundrum. It is primarily characterized by apparently dysfunctional decrements in positive affectivity and losses in the experience of pleasure (Clark, 2000), and yet it has many of the features of a behavioral adaptation (i.e., a species typical set of behaviors that have evolved to solve an adaptive problem). Depressed mood is ubiquitous, affecting most individuals from time to time (Izard, 1991). It is also reliably activated by specific kinds of contexts or circumstances, such as major defeats and losses (Oatley, 1992). Moreover, it appears that those who show a reduced capacity for depressed mood, or mood variation in general, such as those with hypomanic personality (Klein, Lewinsohn, & Seeley, 1996) or with specific types of damage to the prefrontal cortex (Damasio, 1994), are less able to adapt to changing social circumstances. For example, those with hypomanic personality appear unable to maintain stable interpersonal relationships and can be injudicious in their assessment of risk (Klein et al., 1996). However, how depressed mood might be adaptive remains unclear.
