Association between physical exercise and mental health in 1·2 million individuals in the USA between 2011 and 2015: a cross-sectional study Adam Chekroud, Sammi Chekroud, Ralitza Gueorguieva, Harlan Krumholz, John Krystal, Martin Paulus, Amanda Zheutlin in The Lancet (August 08, 2018) Journal Article 1 exercise health