Crank up the volume on Wedding Crashers: According to numerous studies, laughter is almost as effective as exercise on physical and mental well being.

Scientists attribute the benefits of laughter primarily to its ability to combat the physical and emotional characteristics of chronic stress, which has been shown to suppress the body's immunity.

Lee Berk, assistant professor at Loma Linda University in California and a pioneer in laughter research, has found that laughter may reduce stress by increasing the body's secretion of growth hormone, which has a positive effect on immunity.

Laughter also decreases the release of adrenaline and cortisol, two of the worst culprits in weakening the immune system. Berk's studies also suggest that, similar to exercise, busting a gut releases endorphins, which the body uses to fight pain and depression.

Research done by Dr. Michael Miller at the University of Maryland Medical Center, suggests laughter is further similar to exercise in that it decreases blood pressure, increases muscle flexion, improves overall performance of the heart's muscular functions and possibly wards off heart disease.

Roberta Gold, recreation and humor therapist based in California, said the physiological processes the body undergoes during laughter are relaxing.

"Your circulatory system works better, you oxygenate your blood better," she said. "You feel better afterwards, physiologically and emotionally."

Gold suggests the benefits of comedy aren't just physical. While laughter improves the body's physiological processes, a sense of humor is paramount to mental health, she said.

Research at the University of North Carolina determined that a positive mental state -- such as one brought on by humor -- increases open-mindedness, creativity and capacity to adapt to change. Laughter plays a role in these traits because it stimulates positive emotions and encourages a more positive outlook, Gold said.

Experts also speculate that a sense of humor goes hand in hand with higher levels of "emotional intelligence," which determine a person's ability to handle their feelings and understand others' emotional states.

Humor has also been linked to improved test scores. In a study at Johns Hopkins University Medical School, researchers divided students in a graduate biostatistics class into two groups. They administered identical exams to each group, except that one set of tests had humorous instructions. Students who received the amusing exam scored significantly higher than those with the ordinary directions.

So how does laughter get brain juices flowing? Scientists speculate that humor stimulates the brain's reward center in the same ways as sex and chocolate. In turn, this reward center may release dopamine, a chemical that stimulates the frontal lobe, where we do most of our thinking.

Humor and laughter: what is known for sure:

Improve respiration and breathing

Increase pain tolerance

Reduce stress, anxiety and tension

Decrease depression, loneliness and anger

Improve mental functioning (alertness, creativity and memory)

What isn't known yet:

Decrease symptoms of illness

Prevent Pain

Increase life span

Decrease heart disease

Boost immunity enough to fight viral and bacterial infections and disease