The answer, at least for judgments of more consequence than where to take one's next holiday, is that the effects are real but mutable.

FORBES: Side Lines

Those planning on flying this holiday may experience short-term side effects from fatigue and increased cortisol levels, the report details.

FORBES: Why Holiday Travel Makes You Dumb

The effects of September 11 on sales of merchandise could stretch well into the Christmas holiday, as well.

CNN: Attacks force pop culture to step back