From ScienceDaily.com:

Ever crave laughter when you are sick, stressed, or bored? Your body may be trying to help itself. In 2006, researchers from Loma Linda university began studying the interaction between brain, behavior and the immune system. What they found then was that simply anticipating a mirthful laughter experience boosted health-protecting hormones. Now two years later a new finding emerges: those who anticipate positive laughter actually experience a reduction in three damaging stress hormones (known to weaken the immune system). Dr. Lee Berk, lead researcher on the study, believes that “by seeking out positive experiences that makes us laugh, we can do a lot with our physiology to stay well.”

The researchers studied 16 healthy fasting male volunteers for cortisol and catecholamine level changes. The participants were assigned to either the control group or the experimental anticipation-humor group. Blood draws were taken as the experimental group anticipated watching a humorous video (the control group did not anticipate watching such a video). They found that anticipation of laughter reduced levels of three stress hormones: Cortisol (termed “the stress hormone”), epinephrine (also known as adrenaline) and dopac, a dopamine catabolite (brain chemical which helps produce epinephrine). There was no reduction in these hormones for the control group.

Lee Berk presented the team’s findings at the 121st Annual Meeting of the American Physiological Society, part of the Experimental Biology 2008 scientific conference in San Diego earlier this month.

Further Reading:

American Physiological Society (2008, April 10). Anticipating A Laugh Reduces Our Stress Hormones, Study Shows. ScienceDaily.