Jacob Sullum weighs in on the panic over bath salts:

Stories about psychoactive substances that transform people into irrationally violent monsters with superhuman strength have been tied to various chemical agents over the years, including cocaine, PCP, methamphetamine, and even marijuana. They always prove to be grossly exaggerated, if not utterly fictitious. 

A 1989 analysis of "crack-related homicides" in New York City, for example, found that the vast majority of the violence stemmed from black-market disputes, as opposed to the drug's psychoactive effects. After finding only three documented cases in which people under the influence of PCP alone had committed acts of violence, the authors of a 1988 literature review concluded that  "PCP does not live up to its reputation as a violence-inducing drug."