Fact: Marijuana does not cause people to use hard drugs. What the gateway theory presents as a causal explanation is a statistic association between common and uncommon drugs, an association that changes over time as different drugs increase and decrease in prevalence. Marijuana is the most popular illegal drug in the United States today. Therefore, people who have used less popular drugs such as heroin, cocaine, and LSD, are likely to have also used marijuana. Most marijuana users never use any other illegal drug. Indeed, for the large majority of people, marijuana is a terminus rather than a gateway drug.