The media (Time, Daily Mail) are touting a new study published July 14 in the Proceedings of the National Academy of Sciences that is said to link cannabis use to anxiety and depression. The researchers studied the brains of 24 marijuana "abusers"—defined as those who smoke multiple times a day—and how they reacted to methylphenidate (more commonly known as Ritalin), a stimulant used to treat ADHD and narcolepsy. Using personality tests and brain imaging, the researchers found the cannabis users had "blunted" (no pun intended, we hope) behavioral, cardiovascular and brain responses to methylphenidate compared with control participants. The "abusers" also scored higher on negative emotional reactions. The researchers conclude that cannabis interferes with the brain's reaction to dopamine, the chemical responsible for feelings of reward and pleasure.