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In this Aug. 21, 2015 photo, multiple sclerosis patient and author of the memoir "One day at a Time," David Sloan, who is a medical marijuana patient, exhales smoke from medical cannabis concentrate given to him with help from his caregiver, at Sloan's home in Highlands Ranch, south of Denver. Marijuana researchers have predominantly looked at how the drug affects young, developing brains. But increased pot use by older adults has scientists calling for more study of how aging influences drug use, and whether elderly pot users face potential health benefits or risks. (AP Photo/Brennan Linsley)


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