Since the discovery of its psychedelic properties in 1943, lysergic acid diethylamide (LSD) has been explored by psychiatric/therapeutic researchers, military/intelligence agencies, and a significant portion of the general population. Promising early research was halted by LSD's placement as a Schedule I drug in the early 1970s. The U.S. Army and CIA dropped their research after finding it unreliable for their purposes. NSDUH estimates that more than 22 million (9.1% of the population) have used LSD at least once in their lives. Recently, researchers have been investigating the therapeutic use of LSD and other psychedelics for end-of-life anxiety, post-traumatic stress disorder (PTSD), cancer, and addiction treatment. Adverse psychedelic reactions can be managed using talkdown techniques developed and in use since the 1960s.