There is extensive research on laughter publically available showing vast benefits of laughter and the need for making laughter the important part of our daily life.
https://www.ncbi.nlm.nih.gov/pubmed/27439375 - Therapeutic Benefits of Laughter in Mental Health: A Theoretical Review. (Yim J. - 2016)
https://www.ncbi.nlm.nih.gov/pubmed/2556917 - Neuroendocrine and stress hormone changes during mirthful laughter. (Berk LS, Tan SA, Fry WF, Napier BJ, Lee JW, Hubbard RW, Lewis JE, Eby WC - 1989)
https://www.ncbi.nlm.nih.gov/pubmed/1596112 - The dynamics of laughter. (Davidhizar R, Bowen M - 1992)
https://www.sciencedaily.com/releases/2017/06/170601124121.htm - Social laughter releases endorphins in the brain. (University of Turku 2017)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4255480/ - The social life of laughter. (Sophie Scott, Nadine Lavan, Sinead Chen, Carolyn McGettigan - 2014)
http://www.npr.org/sections/ed/2014/08/06/336360521/play-doesnt-end-with-childhood-why-adults-need-recess-too - Play doesn’t end with childhood: why adults need it too - (2014)
(http://internationalpsychoanalysis.net/wp-content/uploads/2011/06/9.-Joan-Erikson-Importance-of-Play.pdf) - (Joan M Erikson on The importance of play in adulthood, an interview with Joan M Erikson 1902 - 1997) by Daniel Benveniste
http://www.cfp.ca/content/55/10/965.short - Laughter Prescription (William B Strean - 2009)
https://www.ncbi.nlm.nih.gov/pubmed/21920973 - Social laughter is correlated with an elevated pain threshold. (Dunbar RI, Baron R, Frangou A, Pearce E, van Leeuwin EJ, Stow J, Partridge G, MacDonald I, van Vogt M - 2012)
https://www.ncbi.nlm.nih.gov/pubmed/21280463 - The therapeutic value of laughter in medicine (Mora-Ripoli R - 2010)
https://www.omicsonline.org/open-access/effects-of-laughter-therapy-on-anxiety-stress-depression-and-quality-of-life-in-cancer-patients-1948-5956-1000362.php?aid=60533 - Effects of Laughter Therapy on Anxiety, Stress, Depression and Quality of Life in Cancer Patients (Melike Demir - 2015)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5037252/ - Laughter is the best medicine? A cross-sectional study of cardiovascular disease among older Japanese adults (Kei Hayashi, Ichiro Kawachi, Tetsuya Ohira, Katsunori Kondo, Kokoro Shirai, Naoki Kondo - 2016)
http://www.bbc.co.uk/news/science-environment-14889165 - Study reveals laughter really is the best medicine (2011)
https://www.ncbi.nlm.nih.gov/pubmed/22894892 - Effect of laughter yoga on mood and heart rate variability in patients awaiting organ transplantation: a pilot study. (Dolgoff-Kaspar R, Baldwin A, Johnson MS, Edling N, Sethi GK - 2012)
http://www.bbc.co.uk/programmes/b03bdpl5 - iplayer Radio 4 Sophie Scott on The Life Scientific (2013)
https://www.theguardian.com/commentisfree/2012/jul/03/laughter-on-the-brain-science - Laughter on the brain: the science behind our sniggers (Sophie Scott 2012)
(http://www.bbc.co.uk/news/science-environment-14889165) - Study reveals laughter really is the best medicine (2011)
http://www.ucl.ac.uk/news/news-articles/1001/10012601 - Sophie Scott from University College London (UCL) says laughter is a universally recognised social emotion, and it is physically contagious.
Learning and Laughter – Sophie Scott
http://www.llu.edu/news/today/today_story.page?id=1621 - LLU researcher finds that anticipating happy times may have health benefits. Lee Berk, DrPH at Loma Linda University professor
http://www.medicalnewstoday.com/articles/276042.php - Laughter may be the best medicine for age-related memory loss (2014)
Dr Lee Burk, co-author of the recent study conducted in Loma Linda University, California, suggested that the less stress a person has, the better their memory performance, and humour may be the key to reducing stress levels.
National Geographic : Is Laughter the Best Medicine?