Smoking hash increases the chances of later heavier drug use in young people

Young people who smoke hash or marijuana risk developing greater neurobiological sensitivity to heavier drugs like heroin. Several epidemiological studies support the gateway hypothesis, which states that cannabis smoking at a young age is a gateway to other kinds of drug abuse later in life. However, it has not been ascertained whether it is cannabis per se that increases the risk of other drug abuse or whether common underlying social or hereditary risk factors make cannabis users more prone to it. "We wanted to empirically test the gateway hypothesis in the absence of social and moral factors," says scientist Maria Ellgren at the Department of Clinical Neuroscience. "All addictive drugs affect the brain’s reward system, and our question was therefore whether cannabis exposure causes molecular and neurochemical changes that give a greater reward effect from other narcotics." The study was conducted on rats at an age corresponding to the teenage years in humans.