A study quietly published in the Annual Review of Sociology in 1998 drew new attention this week when the Prevention File, a drug treatment and prevention industry journal, interviewed its author, highlighting the study's conclusion that there is little evidence that using illegal drugs causes violent behavior.
The study, conducted by researchers at the Robert Presley Center for Crime and Justice Studies at the University of California at Riverside was based on a comprehensive review of the scientific literature on drugs, alcohol and violence. "Despite a number of published statements to the contrary, we find no significant evidence suggesting that drug use is associated with violence," the study concluded.
The study examined four drugs commonly associated with violence -- heroin, cocaine, amphetamines, and PCP (phencyclidine). For heroin, the study found that any evidence of a link between the drug and violence is "virtually nonexistent." The researchers found rare cases of "toxic psychosis" associated with amphetamine abuse, but reported that the association is more likely "situational" than pharmacological. For PCP, which has been widely portrayed as inciting users to violence, the researchers found that that association was based primarily on case studies of people with underlying mental problems. "Emotionally stable people under the influence of PCP probably will not act in a way very different from their normal behavior," the study said.
The strongest link between drug use and violence was with cocaine, the researchers reported. Users sometimes develop paranoia and irrational fears that could push them to violent acts, the study noted. But Robert Nash Parker, the study's principal author, told Prevention File that even that link is unclear. "The conclusions of researchers whose findings support this idea universally highlight a social rather than a pharmacological basis for the link," Parker said. He added that for any drug, the evidence suggests that the social environment plays a greater role in causing violent behavior than pharmacological factors.
Based on its reading of the research and its conversation with Parker, Prevention file noted bluntly, "alcohol outclasses the array of illegal drugs as the substance most associated with violence." It cited an oft-quoted survey of crime victims that showed more than one-quarters of assailants in violent crimes were under the influence of alcohol, while less than 10% were using an illegal drug. According to the Presley Center study, alcohol is "overwhelmingly" the drug most associated with homicides.
"If you really want to have an effective policy related to substance abuse, if you want to have fewer bad outcomes in terms of health, welfare, and violence, the substance you want to focus on is alcohol," said Parker. "The evidence is pretty powerful and pretty convincing if someone is willing to look at it," he added.
Parker's research has caused him to reexamine US drug policy, he told Prevention File. "I think the states are taking a look at the kind of spending they've been engaging in for the last 10 years or so," Parker said. "A lot of that spending has been driven by the very unfortunate policies that emphasize putting drug offenders away for relatively long periods of time. People are coming to see that this has had very little impact in terms of reducing drug use, and the cost is quite enormous."
Parker's report adds further weight to the findings of previous research. For example, a 1994 "Research in Brief" publication by the National Institute of Justice arrived at similar conclusions (http://www.druglibrary.org/schaffer/GovPubs/psycviol.htm).