> Even occasional users show a slight negative Delta IQ in the tables.
So, this is true. But it's also lacking context: that same table also shows a nearly identical gain for adolescents who didn't smoke marijuana at all, suggesting that the negative results for the "used, never regularly" cohort are within the margin of error.
Also consider the scale: the authors say that -0.38SD corresponds to a decline of ~6 IQ points; that means that usage cohorts 1, 2, and 3 each declined by less than 3 points. I'd have to do more background reading, but I suspect that creeps into confidence interval territory. Similarly, we are left without a good explanation for the relatively smaller decline in IQ for the 2 waves cohort. By and large, not confidence inspiring.
> Perhaps you're okay with taking something that makes you even the slightest bit dumber, but I am not.
I'm not okay with taking things that'll make me dumber. However, I'm not convinced that marijuana usage, on par with* reasonable alcohol consumption, would make me dumber. Beyond that, I am confident that several other environmental factors are far more important: absence of lead paint, proper early-life nutrition, &c.
> Do you think kids should be allowed to make this mistake when they don't understand this difference?
I take issue with framing it as a mistake. Per my anecdote, I think that adolescents harm themselves more in a culture that treats alcohol and marijuana as taboos. We should definitely put effort towards stopping adolescent addiction; I think our efforts there will benefit greatly from a culture shift.
* Edit: "on par with" meaning "suitably scaled," not "one joint per beer" or something silly like that.
So, this is true. But it's also lacking context: that same table also shows a nearly identical gain for adolescents who didn't smoke marijuana at all, suggesting that the negative results for the "used, never regularly" cohort are within the margin of error.
Also consider the scale: the authors say that -0.38SD corresponds to a decline of ~6 IQ points; that means that usage cohorts 1, 2, and 3 each declined by less than 3 points. I'd have to do more background reading, but I suspect that creeps into confidence interval territory. Similarly, we are left without a good explanation for the relatively smaller decline in IQ for the 2 waves cohort. By and large, not confidence inspiring.
> Perhaps you're okay with taking something that makes you even the slightest bit dumber, but I am not.
I'm not okay with taking things that'll make me dumber. However, I'm not convinced that marijuana usage, on par with* reasonable alcohol consumption, would make me dumber. Beyond that, I am confident that several other environmental factors are far more important: absence of lead paint, proper early-life nutrition, &c.
> Do you think kids should be allowed to make this mistake when they don't understand this difference?
I take issue with framing it as a mistake. Per my anecdote, I think that adolescents harm themselves more in a culture that treats alcohol and marijuana as taboos. We should definitely put effort towards stopping adolescent addiction; I think our efforts there will benefit greatly from a culture shift.
* Edit: "on par with" meaning "suitably scaled," not "one joint per beer" or something silly like that.