After subjects watched humorous clips, researchers saw decreases in stress hormones. (Reuters)

When people laugh repetitively, their bodies respond as if they exercised, a small new study suggests.

At an experimental biology conference in California this week, Dr. Lee Berk presented his research suggesting watching comedy may be good for your health.

"You can sit on the couch and get some of the same or similar benefits relative to exercise," said Berk, a preventive care specialist and psychoneuroimmunology researcher at Loma Linda University's schools of allied health and medicine.

Berk has studied the effects of laughter on human physiology for years. He has found that people who repetitively laugh, ideally for at least 20 or 30 minutes a day, can reap some of the same benefits as people who exercise. These include lower blood pressure and levels of low-density lipoprotein or LDL "bad" cholesterol, increased production of antibodies and, not surprisingly, improved mood.

In the latest research, 14 healthy volunteers were recruited for a three-week study that examined the effects of both laughter and distress on key hormones.

During the study, each subject watched either the tense first 20 minutes of the movie Saving Private Ryan or their choice of a variety of humorous 20-minute video clips, including stand-up comedy and movie comedies. After one week, the volunteers watched the opposite genre of video.

The subjects' blood pressure was measured and blood samples taken immediately before and after they watched the videos.

"We know there's a decrease in cortisol and we see decreases in epinephrine," Berk said of the findings after the funny clips. "Those are stress hormones in the blood." No significant effect on the hormones was seen after subjects watched the distressing video.

The findings make sense to Jana Sawynok, a pharmacologist at Dalhousie University in Halifax who is doing research on alternative medicine. The problem is, no one really understands why laughter causes physiological changes or how to harness them.

"Certainly, if we looked for changes in the bloodstream, we could probably find them, but I think we're a very far distance from recommending that as a treatment," Sawynok said.

The study had a small sample size and the idea needs further research, Berk said.