About one in three adult hospital stays in 2012 involved a mental or substance-use disorder, according to a new report by the Agency for Healthcare Research and Quality. The estimate excludes neonatal and maternal stays. Patients with a primary mental or substance-use disorder diagnosis were twice as likely to be uninsured as other patients, and were often more likely to be admitted through the emergency department. The findings are based on data from the Healthcare Cost and Utilization Project’s National Inpatient Sample.