The gateway theory is "any mood-altering drug, as a stimulant or tranquilizer, that does not cause physical dependence but may lead to the use of addictive drugs, as heroin" (Dictionary.com). There have been some studies done that have come to the conclusion that marijuana is a gateway drug, but a majority of those studies only focus on adolescents whose brains and bodies are still developing which can alter the results. .
What critics fail to mention is why marijuana is considered a gateway drug. Marijuana is a gateway drug through association, not by scientific proof. In fact, a twelve year study done by the American Psychiatric Association shows that adolescents who used marijuana before using other substances weren't any more or less likely to have substance addictions later in life than those who didn't use marijuana before hand. The reason marijuana has gotten the name of "the gateway drug" is because in order for someone to get marijuana, they must go to a dealer. The dealer most likely has "harder" drugs like cocaine or heroin, making access to those drugs easy, not to mention the dealer will definitely encourage the purchase of other drugs. Legalizing marijuana would take dealers completely out of the picture. In fact marijuana is now being called an "exit drug." In Oakland, California, the alcoholics anonymous and narcotics anonymous groups have been using marijuana to get off addictive substances (Oaklanders Quitting Oxycotin With Marijuana). .
Cannabis has benefitted the world of medicine for thousands of years. Over two-thousand years ago, China was using the cannabis plants to help with all kinds of disorders like head and stomach aches (Grolier). Also, even before the tenth century AD, East Indian healers would use marijuana for a multitude of different things (Grolier). That was far before modern medicine and technological advances but many doctors say that medicine should go back to basics.
