Chronic stress is correlated with increases in stress hormones cortisol and cathecolamines. There is strong scientific evidence linking negative emotional states like depression, anxiety, or anger with increased risk for cardiovascular disease. However, much less is known about the association between positive emotional states, the so called eustress, like laughter and happiness. The nicest of all laughter types is associated with humor and it is specified as mirthful laughter.
In this respect there are some studies made by Berk and colleagues, from the Loma Linda University, demonstrating that in comparison with chronic stress mirthful laughter reduced the levels of Cortisol by 39%; adrenaline by 70% and dopac by 38%. The conclusion in one of their papers was that humor appears to attenuate catecholamines and MI recurrence and thus could be an effective adjunct in post-MI care (1, 2, 3).
On the other hand Michael Miller, from the University of Maryland, presented a study at the European Society of Cardiology in the 2011 Congress (4) highlighting the link between endothelial function and laughter. His study showed that when people laughed their major blood vessels dilated allowing for easier blood flow, that indicates a reduced risk of cardiac events.
Dr. Miller’s idea to study positive emotions such as laughter came after studies that had shown that mental stress caused blood vessels to constrict. His first study about sense of humor and coronary artery disease was published in 2001 (5). In other paper, published in 2009 (6), he told about the tests made to confirm the hypothesis that mirthful laughter also favorably affect endothelial dependent flow-mediated vasodilation (FMD). In this way volunteers were randomized for two different phases in a randomized-crossover design. One phase included watching a movie or segment of popular comedies (ex: Saturday Night Live) whereas a second phase was to view a movie known to promote mental stress (ex: The opening segment of “Saving Private Ryan”). The assessment of endothelial dependent vasoreactivity was performed using high resolution ultrasound of the brachial artery, also referred as brachial artery reactivity test (BART). A total of 160 BART measurements were performed and demonstrated a divergent effect after watching a movie provoking mental stress as compared to mirthful laughter. Specifically, a 35% reduction in FMD compared to baseline followed mental stress whereas a 22% increase in FMD occurred in response to laughter (7). In 2008, Dr. Miller and colleagues, in an oral presentation entitled “Positive emotions and the endothelium: Does joyful music improve vascular health?”, made at the American Association Scientific Sessions, on 11/11/2008, conclude that the cardiovascular benefits of music are similar to those found in their previous study of mirthful laughter (8)
Dr. Sugawara and colleagues in 2010 have confirmed the findings from Dr. Miller saying that their results suggest mirthful laughter elicited by comic movies induces beneficial impact on vascular function (9).
Again, in the presentation made by Dr. Miller at the ESC, 2011, volunteers watched segments of a funny movie, such as the farce “There's Something About Mary” on one day and on another day watched the opening segment of the stressful movie “Saving Private Ryan”. When study volunteers watched the stressful movie, their blood lining developed a potentially unhealthy response called vasoconstriction, reducing blood flow. Overall, in this time, more than 300 measurements were made with a 30-50% difference in blood vessel diameter between the laughter and mental stress phases (4).
We think the above studies give additional evidence to our acidity theory of atherosclerosis (10), that has the following sequence of events:
I. Sympathetic dominance by continuous stress plus
II. Deficiency in production of endogenous digitalis-like compounds (DLCs) with alterations of Na(+), K(+)-ATPase activity results in:
III. Lowered pH (acidity) that increases perfusion pressure and provokes effects on contractility of coronary arteries leading to changes in hemodynamic shear stress and atherosclerosis as consequence.
Sympathetic activation, metabolic acidosis and vascular reactivity The studies by Berk and Miller confirm previous studies suggesting that the sympathetic activation with elevation of circulating catecholamine (adrenaline, etc..), cause coronary vasoconstriction and consequent reduction in blood flow.
On the other hand it is interesting to notice that increased lactate (or decreased blood pH) may evoke vascular smooth muscle relaxation and increase of blood flow (11).
These opposite forces working in sequence - with the sympathetic overdrive leading to metabolic acidosis -, in our view, may be reconciled to partially explain the occurrence of the resulting abnormal stretching/relaxing of coronary arteries, in different directions, simultaneously, producing atherosclerosis (10).Carlos Monteiro
1. Berk LS, Tan SA and Berk B. Cortisol and cathecolamine stress hormone drecrease is associated with the behavior of perceptual anticipation of mirthful laughter. The FASEB Journal. 2008; 22;946.11
2. Tans SA, Berk LS et al. Humor as an adjunct therapy in cardiac rehabilitation, attenuates cathecolamines and myocardial infarction recurrence. Adv Mind Body Med 2007; 22(3-4): 8-12
3. Berk LS et al. The neuroendocrine and stress hormone changes during mirthful laughter. Am J Med Sci 1989;6:390-396
4. Miller M. Laughter and vascular function, ESC 2011.
5. Clark A, Seidler A, Miller M. Inverse association between sense of humor and coronary heart disease. Int J Cardiol. 2001 Aug; 80(1):87-8
6. Miller M, Fry WF. The effect of mirthful laughter on the human cardiovascular system. Med. Hypothesis 2009; 73(5):636 . Full free text at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2814549/pdf/nihms-154943.pdf
7. Miller M, Mangano C, Park Y, et al. Impact of cinematic viewing on endothelial function. Heart 2006; 92:261-262
8. Miller M, Beach V, Mangano C, Vogel RA. Positive emotions and the endothelium: Does joyful music improve vascular health? American Association Scientific Sessions, on 11/11/2008
9. Sugawara et al. Effect of mirthful laughter on vascular function. Am J Cardiol 106:856-9 (2010).
10. Carlos ETB Monteiro, Acidic environment evoked by chronic stress: A novel mechanism to explain atherogenesis. Available from Infarct Combat Project, January 28, 2008 at http://www.infarctcombat.org/AcidityTheory.pdf
11. Celotto AC, Capellini VK et al. Effects of acid-base imbalance on vascular reactivity. Brazilian Journal of Medical and Biological Research (2008) 41:439-445 Full free text at http://www.scielo.br/pdf/bjmbr/v41n6/7099.pdf
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