Heavy marijuana use among youths is leading to more addiction and antisocial behavior. ... Mass shooters at Rep. Gibby Giffords’s constituent meeting in Tucson, Ariz. (2011), a movie theater in Aurora, Colo. (2012), the Pulse nightclub in Orlando, Fla. (2016), the First Baptist church in Sutherland Springs, Texas (2017), and Marjory Stoneman Douglas High School in Parkland, Fla. (2018), were reported to be marijuana users. It could be a coincidence, but increasing evidence suggests a connection. THC, the chemical that causes a euphoric high, interacts with the brain’s neuron receptors involved with pleasure. Marijuana nowadays on average is about four...