Can I be affected (or get stoned) if someone around me is smoking cannabis?

Every time I believe someone is using cannabis near me, I become anxious and fearful that I may experience the same effects of the drug, as has the user. Is this fear irrational? Furthermore, can the effects of being merely exposed to the smoke of cannabis cause noticeable or even negligible effects to the developing brain?

It sounds as though you are someone who has never used a drug like cannabis and you have no intention of ever doing so. If that is the case, it is no surprise that being around those using the drug could worry you. In most parts of the world cannabis is still an illegal drug and being around people who are breaking the law can often result in problems for you, even if you're not actually involved. But as far as the risk of being affected by cannabis due to exposure to the drug by others smoking around you ('passive cannabis smoking'), from what we know from current research it should not be a major concern.

Just being in a room where people are smoking and the smell of cannabis is in the air is not sufficient to cause effects and you should not be worried about such levels of exposure. If you are in a very confined space that is not well ventilated, it is possible, however, to experience mild intoxication from inhaling the smoke of others. Even then, the effect would be at much lower levels. An effect is more likely to be experienced when the newer, stronger strains of cannabis are smoked as they contain higher levels of THC (the chemical that produces the high) that can be found in side-stream and exhaled smoke. Realistically, however, this is a situation that can, and should be, avoided.

The simplest thing to do if you suspect someone is smoking or vaping cannabis near you and that you may be exposed to smoke or vapour is to move away, or excuse yourself politely if you know the person. If you don't feel comfortable about being honest with them and telling them about your concerns, say that you are allergic to the smoke/vapour or you're worried about the smell of the smoke getting onto your clothes or into your hair. Alternatively, simply make an excuse to leave the room when they're using the drug. Even though the risk of being affected by the drug is low, if being around someone who is smoking the drug causes you to become anxious, avoid the situation when you can - it's just not worth the worry!