The combination of prescribed central nervous system stimulants, such as drugs that relieve ADHD symptoms, with prescribed opioid medications is associated with a pattern of escalating opioid intake, a new study has found. The analysis of health insurance claims data from almost 3 million U.S. patients investigated prescribed stimulants’ impact on prescription opioid use over 10 years, looking for origins of the so-called “twin epidemic” of combining the two classes of drugs, which can increase the risk for overdose deaths.