Could one try of cannabis have affected my school grades?

Having read your answer to "can smoking weed once have a lasting effect" I was wondering how obvious, after having smoked once, any negative long-term effects would be. If I can't say for certain that there are long- term effects does that mean that there aren't any or just that they are too subtle to perceive? Basically, I smoked cannabis once and since then I have noticed school grades going down (like from 100s to 95s), is this probably just in my head?

Some people who experiment with an illegal drug, whether it be cannabis, ecstasy or whatever, do not necessarily have the experience they were expecting. As a result, many will choose never to use the drug again. In some cases, particularly if their experience was unpleasant, people are tempted to 'over-analyse' what happened and start to stress about what impact the drug had on them and could potentially have on them in the future.

Realistically, the most likely negative effect of smoking cannabis just once is having an accident when intoxicated or making a fool of yourself in front of your friends. Some people who have used only once, but perhaps smoked too much or unknowingly used a high THC product, may have extremely unpleasant effects. They could feel faint as the drug causes a drop in blood pressure, become paranoid, anxious or nauseous. In extreme cases, some first time users may even vomit. In these cases, it becomes obvious to the person experimenting with cannabis that it is not a 'harmless' drug (i.e., things can go wrong) and, as a result, they'll choose to never use the drug again.

You ask specifically about long-term effects that are "too subtle to perceive" and highlight how your experience could have affected your school grades. Could that 'one try' have resulted in an effect on your school performance? Most probably not ...

You have obviously been performing at an extremely high level and any drop, no matter how small, is noticeable but this change has much more likely explanations. Focus on the reason you decided to smoke cannabis in the first place and whether it was associated with other new activities or challenges that were happening around the time you decided to experiment. It could be one of these, or even a combination of all of them, that could explain the slight change in school marks.

You are obviously concerned about your grades and that is the first step to maintaining or even improving them. You might like to talk with your school counsellor about anything else that might be concerning you and causing you to worry about your once-only cannabis use.