According to an article recently published in Alternative Therapies in Health and Medicine, laughter may reduce stress and increase natural killer cell levels, a type of white blood cell that attacks cancer cells.

Many people experience stress as part of their daily lives. Individuals with health issues, particularly diseases like cancer, often experience a significant increase in their stress levels following a cancer diagnosis. This elevated stress may continue during treatment and after its completion. A few studies have suggested that stress appears to negatively impact health. Other research has reported that a weak immune system, as measured by low numbers of natural killer cells, appears to decrease patient resistance to disease and increase likelihood of death among cancer patients.

Researchers are beginning to investigate therapies that may alleviate stress and correspondingly improve immune response. Most of these therapies are considered complementary and alternative medicine (CAM). Mind-body interventions, a type of CAM, are often used to address stress issues. These techniques claim to alter a patient’s mental state and create a corresponding shift in their physical body. Examples of mind-body interventions include meditation, music therapy, and laughter.

Most people would say they feel better during, or immediately following, a bout of laughter. Patch Adams, a doctor well-known for his advocacy of laughter and humor in hospitals, has gone so far as to start a free hospital in rural West Virginia. In Japan, laughter clubs are becoming more popular. Interestingly, a survey of rural Midwestern cancer patients reported that humor was one of their most frequently used CAM therapies.

Scientists are also beginning to explore laughter by conducting clinical trials that measure specific changes in psychological and physical well-being that appear to result from laughing. In one study, conducted at the Indiana State University Sycamore Nursing Center, 33 healthy adult women were divided into two groups. The treatment group watched a humorous video, while the control group viewed a tourism video. All participants completed questionnaires regarding their stress and humor levels before and after watching their videos. In addition, blood drawn before and after treatment was tested for natural killer cell levels.

Compared to the control group, the laughter group reported a significant decrease in stress following treatment. Their stress level appeared inversely correlated with their level of mirthful laughter. Participants with high scores on the humor questionnaire also had significantly higher numbers of natural killer cells after treatment. The laughing participants’ natural killer cell levels were significantly higher than those of the control group too.