Randall Parker has the scoop. Here is one excerpt, quoted by Randall:
…when confronted with thoughts of death, people tend to act in ways that will boost their self-esteem. They also have fewer cognitive resources to resist behaviors that are not central to their self-image. People for whom being slim or fit is important to their self-image, for instance, will not be as likely to overeat, but if physical appearance isn’t as important, the willpower to resist that fudge sundae will plummet.
Here is my previous post, with an assist from Robin Hanson, on the same topic. Let me note in passing, this is one reason why I would expect a bimodal response to a major crisis such as avian flu. Most people will behave quite heroically; those who take pride in being social rebels/misfits will act like scoundrels.