Background: Catecholamines, especially epinephrine, are implicated in causing arrhythmias, hypertension, and recurrence of myocardial infarction (MI). Diminishing or blocking the effect of catecholamines is useful in cardiac rehabilitation. We have shown previously that a single one-hour episode of mirthful laughter attenuates epinephrine production. Design: We hypothesized that daily participation in mirthful laughter would diminish catecholamine production and improve cardiac rehabilitation. Methods: Forty-eight diabetic patients who had recent MI were randomly divided into two matched groups, and followed for one year in their cardiac rehabilitation programs. The experimental laughter group was asked to view self-selected humor for 30 minutes daily as an adjunct to their standard cardiac therapy. Blood pressure, urinary and plasma epinephrine and norepinephrine levels, and 24-hour Holter recordings were monitored monthly in both experimental and control groups. Results: The patients in the laughter group had fewer episodes of arrhythmias, lower blood pressure, lower urinary and plasma epinephrine and norepinephrine levels, less use of nitroglycerin for angina and a markedly lower incidence of recurrent MI (2/24, 8.3%) than did the control group (10/24, 42%) Conclusion: Laughter attenuates catecholamines and MI recurrence, and thus can be an effective adjunct in post-MI care.

, 2005; 11(2): BR31-40.