Nocola said:
I know it's a lot less harmful than for example drinking alcohol and smoking cigarettes
Hi there! It's nice to see that you're pursuing information on the topic, so I'd just like to correct something for you, in case no one else has caught this.
It is often said that marijuana doesn't cause as much damage to the lungs as tobacco smoke, but this is largely hyperbole. You see, people are eager to point out the hypocrisy in tobacco & alcohol being legal and widely available while marijuana is illegal. It certainly is a hypocrisy, I won't disagree with that. But it's a hypocrisy because the damage tobacca & marijuana inflict is
comparable, not because marijuana inflicts less damage. People often mistake or exaggerate the relative "harmlessness" of marijuana in order to further their own agendas - usually arguing in favour of legalisation. While marijuana probably shouldn't be illegal, you should be careful which sources of information you trust as fact.
In terms of damage to the lungs and respiratory system by volume inhaled, marijuana is actually considerably more dangerous - however, in the long term, the damage a regular marijuana smoker will sustain to their lungs vs the damage a regular tobacco smoker will incur are comparable for the following reasons:
1. Tobacco smokers tend to smoke much greater volumes of tobacco than their marijuana smoking equivalents.
2. However, this is somewhat offset by the fact that marijuana smokers hold their breath for considerably longer after inhaling (after all, the goal is to get high, not to sate a craving).
3. Tobacco contains high numbers of carcinogens (cancer causing substances) while marijuana does not. Although marijuana is more dangerous in terms of pure damage by volume inhaled, it comes with a lower risk of contracting cancer.
As for the comparison to alcohol, the two can't really be compared. They have entirely different physiological and psychological effects, and the amount of damage one or the other would inflict varies wildly from person to person.
Anyway, I hope I've cleared at least a few things up for you, and I wish you the best of luck in your search for knowledge on this somewhat controversial topic.