University of Maryland Professor of Medicine Michael Miller says that "We don't have any clinical outcome evidence to show that laughter will reduce heart attacks or improve overall survival. However, we do have a number of studies that have shown that there is a potential upside, in terms of vascular benefits and also overall health."  Oxford University researchers have recently found that "laughter triggers an increase in endorphins, the brain chemicals that can help you feel good, distract you from pain and maybe deliver other health benefits."  Lead author Robin Dunbar, an evolutionary anthopologist, notes that "these results back up prior research suggesting that people who laught need less pain medication after surgery..."  The authors all note that "a snicker here and there" is not what triggers the reaction; instead the Oxford study reveals that "endorphins are released only when 'we laugh till it hurts,'"  or until "we end up running out of breath or physically exhausted," according to Dunbar.  See "Laughing is Good for your Health?  It's No Joke,"  The Washington Post (October 25, 2011): E4.  See also "Laughter: A Scientific Investigation," Robert R. Provine, a neuroscientist at the University of Maryland Baltimore County.