The marijuana today is a lot stronger than what people were smoking in the sixties and early seventies. The same is true for cocaine and heroin, both of which are dramatically more potent today. The dangers associated with moving to other drugs are greater now. But the danger associated with progressing to these other drugs is greater today than it used to be. There are more dangerous drugs around now, like crack, ice, PCP, and Rohypnol.
People start using younger today.
In the earlier years of the drug epidemic most people who tried marijuana or other drugs began when they were in their twenties, and subsequently when they were in their late teens. People who use today may begin when they are in their early teens or even younger. We know that those who start younger get into considerably more trouble with their eventual drug use, and they also tend to end up having more of the other problems associated with drug use. The world is a more dangerous place than it used to be. Young people today face more serious hazards in their larger environment than young people did just a generation ago.