Cannabis is the most popular and easily accessible illicit drug in Australia. So people who have used less accessible drugs (heroin, cocaine, LSD) are likely to have first accessed cannabis and other more accessible drugs, including alcohol. But the use of one does not cause the use of another.
Most people who try cannabis never go on to use any other illegal drug, and the vast majority of those who do try another drug don’t become dependent on it, or go on to have associated problems.
For most people, cannabis is an endpoint in drug use rather than a so-called “gateway drug.” New evidence suggests that cannabis can even serve as an “exit drug,” helping people to reduce or eliminate their use of more harmful drugs such as opiates or alcohol by easing withdrawal symptoms.