Tobacco and cannabis (marijuana) can both damage your health and lead you to become dependent on them. Tobacco has been a part of mainstream culture for much longer than cannabis and was for a long time seen as socially acceptable and therefore legal, and once established as legal it's harder to change its status. This was before the health problems from using tobacco were widely known. Since this information has become available, the laws around selling tobacco have changed. For example, it is now illegal to sell tobacco to a minor, and to smoke in restaurants, bars and many public spaces.

There has long been concern that people who try cannabis will go on to other drugs, such as cocaine, heroin and amphetamines, but this has not been proven in research. This has also been used as an argument to legalise cannabis because then buyers would not be exposed to dealers with other drugs. Another legalisation argument has been the opportunity to provide health messages on packaging and making the strength uniform (as happens with alcohol) as well as restricting sales to minors. Cannabis has been made legal in some very limited circumstances overseas for use as a medicine for people with life-threatening illnesses such as cancer and HIV.

Cannabis affects judgment and can seriously impair performance which is why it is illegal to use drugs such as cannabis, and drive. Cannabis can also affect your ability to learn so it is particularly harmful to children and adolescents whose brains are still developing. It has also been linked to problems with mental health, especially for people who already have mental health problems. Because of all the problems with cannabis it is unlikely to be legalised. Instead, we may see more restrictions on who can use legal drugs such as alcohol or tobacco and in what settings they can be used.