A new JACC study indicates that more than two million people who have heart disease have reported using marijuana at some point. “Now that we have seen marijuana use become more popular than tobacco smoking, we need more rigorous research, including randomized clinical trials, to explore the effects of marijuana on cardiovascular health,” review co-author Muthiah Vaduganathan, MD, MPH, of Brigham and Women’s Hospital’s Heart and Vascular Center, said in a press release. The finding that millions of patients have used the substance (shown by national survey data) was part of a review of marijuana use in patients with established cardiovascular disease. The recommended clinical screening.