"Is cannabis really addictive? I'm concerned about how much a friend smokes, but they keep telling me it's not physically addictive. Is that true?"
From Cheech and Chong to Dazed and Confused there have always been ways in which we haven't taken cannabis very seriously: as a drug it can seem harmless.
It's also one of those old ideas: that some drugs are physically addictive, and some are psychologically addictive. I say old because we now know that any pleasurable behaviour can become addictive and that making a distinction between physical and psychological withdrawal is, well, nonsense.
Recently it has been highlighted that there is clearly a growing acceptance of the idea that cannabis should be legal, or decriminalised. This isn't the same thing as saying it's harmless. The fact that it causes harm is actually a reason to change the law and, like we do with alcohol, restrict and regulate access.
However, much like alcohol, cannabis being a socially accepted drug can make it difficult to talk about the problems and potential for addiction whenever anyone picks up a can, or a joint.
The obvious, but uncomfortable, golden rule with these things is: The safest use is no use.
These days when we try and think about the problems associated with drug use, we tend to think about harm. But even that can have its limitations. To talk about harm at the population level tells us something useful about how much potential for damage any one drug has, but it can also cloud the picture at the individual level.
One of the big potential harms is addiction. Cannabis may not be as addictive as other drugs, but for those who struggle to stop it can cause very real harm. When you compare the numbers who try it, versus the numbers who end up in drug treatment, it's clear that it isn't as addictive as heroin, or methamphethamine (P).
But when you talk to individuals who struggle to stop, as I have for many years, it's also clear that for some it can be debilitating.
So in answer to your question, yes, cannabis is addictive, for some. The only way to measure that is to be able to talk with your friend about the impact it may be having on their day-to-day life, and health.
Does it cause them to miss work, appointments or social events? Do they feel unable to socialise without being stoned? Do they feel a need to smoke before they can leave the house? Does the idea of running out of the drug make them feel anxious?
Of course, even if their answer to all these questions is no, and they aren't addicted, it can still cause harm. At the very least smoking it causes health problems. It also costs money. And if you're a teenager it can damage the brain in its development. For some in can "turn on" the gene for schizophrenia.
Personally, I support the legalization, and regulation (with strict age restrictions on sale and purchase) balanced with increased funding for drug treatment. Because while cannabis may be less dangerous than other drugs, it isn't without risk. And it certainly isn't a laughing matter.