Dark as a Dungeon in Depression

Depression has been associated with disruption of circadian rhythms and with hyperactivity of proinflammatory cytokines like interleukin (IL)-6 (see JW Psychiatry Mar 29 2010). In a series of experiments, researchers examined the relationship between these phenomena in mouse models of depression.

Following acclimation to a normal light–dark (LD) cycle, animals stayed for a month in that environment or in constant darkness (DD). Circadian rhythms in the DD mice became desynchronized. With no differences in overall activity, DD mice had more immobility than LD mice in the forced swim and tail suspension tests (two depression models) and less preference for sucrose over water after food deprivation (an anhedonia model). DD mice also had elevate…