How Lead Caused America's Violent Crime Epidemic

"Starting in the 1960s, America saw a huge increase in levels of violent crime that peaked in the early 1990s, then steadily declined, and continues to decline today. All kinds of theories have been promulgated to explain this peak and decline in crime, and plenty of politicians in the 1990s took credit for it. But in what I personally consider to be a tour de force of journalism, Kevin Drum of Mother Jones has summarized all of the available research. All of it points to one simple idea: violent crime rose as a result of lead poisoning because of leaded gasoline. It declined because of lead abatement policies..."
http://www.forbes.com/sites/alexknapp/2013/01/03/how-lead-caused-americas-violent-crime-epidemic/