Marijuana has been shown to decrease motivation. That alone would be enough to lower GPAs. In addition, it precipitates mental illness, notably psychotic disorder. I do not think the data distinguishes between whether the mental illness arises in a susceptible population or whether everyone is susceptible.
In any case, marijuana damages developing brains. This means that people less than age 25 are the most susceptible to marijuana associated brain damage. This is the bulk of the college population.
The societal implications of the widespread push to decriminalize marijuana are likely to be dire. And like any bad direction that society takes, the full effects of decriminalization won’t be felt for years.
And doper refuse to admit there is any downside to mj legalization.
What you posted is factual and even I as a layman have done enough research to have seen all of that and more in my readings.