Ever wondered what Seasonal Affective Disorder actually is? Or if it’s even a real thing? What ca’’s this could be partly due to our ancestors hibernating in winter months. However, not to worry; if the effects of the disorder are really too much, just move to Arizona, the sunniest place in the world. This film is part of our series that provides the blueprint for a scientifically perfect summer. From sweating to hay fever, insects to jet lag, Kate Mulcahy helps you hack summer to engineer the perfect season. Taking a different topic each Thursday, the videos will gradually build up an equation for summer perfection; a summer survival guide certified by science. Subscribe to keep up each week: http://bit.ly/RiSubscRibe References: Kurlansik, S.L. and Ibay, A. D. (2013) Seasonal Affective Disorder. Indian Journal of Clinical Practice. 24(7): 607-610 Revell, V.L. et al (2006) Advancing Human Circadian Rhythms with Afternoon Melatonin and Morning Intermittent Bright Light. The Journal of Clinical Endocrinology & Metabolism 91(1): 54-59 Wehr, T.A. (1997) Melatonin and Seasonal Rhythms. J Biol Rhythms 12: 518-527 http://www.currentresults.com/Weather-Extremes/sunniest-places-countries-world.php Music: Vivacity by Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 http://creativecommons.org/licenses/by/3.0/ Mining by Moonlight by Kevin MacLeod (incompetech.com) Licensed under Creative Commons: By Attribution 3.0 http://creativecommons.org/licenses/by/3.0/ Subscribe for regular science videos: http://bit.ly/RiSubscRibe The Ri is on Twitter: http://twitter.com/ri_science and Facebook: http://www.facebook.com/royalinstitution and Tumblr: http://ri-science.tumblr.com/ Our editorial policy: http://www.rigb.org/home/editorial-policy Subscribe for the latest science videos: http://bit.ly/RiNewslet