Laughter has been described as a kind of “social glue” that binds groups together; it has significant benefits for the individual, too.

A decade ago, Dr. Lee Berk of Loma Linda University in California found that an hour spent watching comedy reduces levels of stress hormones and strengthens the immune system.

Now Dr. Berk and his colleagues have gone further: the mere act of anticipating “mirthful laughter” in the future produces similar positive results.

Volunteers who were told they were going to be shown a humorous video experienced a 27 percent increase in feel-good endorphin levels and up to 70 percent reduction in stress hormones like adrenalin. Control groups who did not anticipate watching such a film had no such changes.

Dr. Berk’s research complements work by Dr. Paul Ekman at the University of California in San Francisco. Dr. Ekman found that deliberately flexing your facial muscles into expressions of warmth, mirth, or joy can produce the same effects on the nervous system as the actual emotions, thereby eliciting them.

Turn up the corners of your mouth and keep a favorite humorous book tucked away in a desk drawer for consultation; it’s worth a try, anyway.