Interesting New York Times article: "Brain Is a Co-Conspirator in a Vicious Stress Loop."
Some key bits from the article:
[...] Nuno Sousa of the [...] University of Minho in Portugal and his colleagues described experiments in which chronically stressed rats lost their elastic rat cunning and instead fell back on familiar routines and rote responses, like compulsively pressing a bar for food pellets they had no intention of eating.
[...The] rodents [became] cognitively predisposed to keep doing the same things over and over, to run laps in the same dead-ended rat race rather than seek a pipeline to greener sewers. "Behaviors become habitual faster in stressed animals than in the [control group], and worse, the stressed animals can't shift back to goal-directed behaviors when that would be the better approach," Dr. Sousa said. [...]
[Stanford neurobiologist] Robert Sapolsky [...] said, "we're lousy at recognizing when our normal coping mechanisms aren't working. Our response is usually to do it five times more, instead of thinking, maybe it's time to try something new."