"In 2007, of the 95 million visits made to the emergency department (ED) by adults in the U.S., 12.0 million (12.5 percent) were related to MHSA," reports the Agency for Healthcare Research and Quality (AHRQ). The summary appears in a press release from the here. Or download the entire report (pdf): Mental Health and Substance Abuse-Related Emergency Department Visits among Adults, 2007.