What is the role of THC here? Presumably THC will change your behavior, and if your behavior over a long period of time impacts IQ or any of the metrics mentioned (e.g., "executive function, processing speed, memory, attention span and concentration...") then it is difficult to say that THC is the direct cause of "damage." When we say that being poor lowers your IQ or decision making capabilities, most infer that this is the result of secondary effects like stress and anxiety rather than your actual wealth alone. Is the message that THC causes damage like cigarette smoking, or like being poor---or both?
This is absolutely not true. There are multiple factors which have been proven to affect an individual's IQ over time-
* Schooling,
* How stimulating their environment is,
* Nutrition,
* Disease (although this is generally towards the negative).
All of these can be influenced by behavior- people's eating habits affect their nutrition, and people who seek out intellectual stimulation are more likely to find it than those who don't.
I'm having trouble reconciling your statement with what I've heard of a variety of behaviours. Having a bad night sleep has a very measurable effect on IQ, and I'm sure there's many others (stress included).
