The Gateway theory
Some argue cannabis is a gateway drug – that its use causes people to also try, more dangerous drugs. This argument is often used to justify ongoing criminalisation of cannabis.
Others say there is no evidence that cannabis causes harder drug use. They argue that cannabis is the first drug used by people with a predisposition to drug use simply because it is the most widely available. In countries where cannabis is not readily available, other drugs fill the role of ‘gateway’ drug. Another argument against is that not all cannabis users go on to use other drugs.
A study by Otago University researcher Professor David Fergusson, found a clear tendency for those using cannabis to record higher usage of other illicit drugs, but concluded this could be due to a number of reasons, such as:
- experience with cannabis encouraging experimentation with other drugs
- people who obtain cannabis become exposed to drug dealers
- cannabis may actually change the brain's chemistry to make young people more likely to try other drugs.
In other research cited by the Health Select Committee's 2003 report into cannabis use in New Zealand, it was found that people who had used cannabis more than 50 times a year were 60 times more likely to try other illicit drugs than young people who had never tried cannabis.
However, this study could not identify a causal link with the Committee report concluding: "These findings suggest that cannabis, when used frequently, may be a 'gateway' drug to other illicit drug use, although whether this is a result of contact with the illegal market or an effect of cannabis use is uncertain."
