According to the US Drug Enforcement Agency, DEA, marijuana is a Schedule 1 category narcotic , which means that it has a greater potential for abuse or addiction than cocaine or methamphetamines, and could produce psychological dependence and severe physics.
But marijuana would not be as harmful as two legal substances: alcohol and tobacco.
68% of tobacco users and 23% of those who drink alcohol eventually develop a dependency, compared to only 9% of those who smoke marijuana.
Although the US Centers for Disease Control and Prevention linking 88,000 deaths to alcohol consumption each year and 480,000 from cigarette and second-hand smoke consumption each year in that country, the effects of marijuana on health – although little studied – are less serious.
However, marijuana can affect developing brains. Studies show that teens who use marijuana sometimes have lower IQ scores and that marijuana can increase psychiatric problems.
So when it comes to responsible legal drinking, alcohol policy is fine: you have to wait until you are of legal age.