Marijuana opponents often say that consuming marijuana makes a person dumber. Many opponents specifically point towards marijuana use as a teenager and try to link it to a lower IQ later in life. Those claims almost always point to a long debunked study that concluded that marijuana use as a teenager would lower a person's IQ 8 points later in life. The results of another study were recently released which concluded that using marijuana as a teenager does not lower one's IQ. Per Oregon Live:
If smoking pot harmed test scores, the researchers reasoned, people who'd smoked more pot should show poorer trends than those who'd smoked less. But that's not what the data revealed. Among users, those who'd smoked more than 30 times or used it daily for more than a six-month stretch didn't do worse.
The study also looked at 290 pairs of twins in which one had used marijuana and the other had not. The members of each pair had grown up together and 137 sets were identical twins so they shared the same DNA. Again, the pot users did not fare worse than their abstaining twin siblings.
So, the researchers concluded, pot smoking itself does not appear responsible for declines in test scores. Isen noted, however, that the work says nothing about other potential harmful consequences of smoking marijuana in adolescence.
Some of the smartest people that have ever lived have consumed marijuana while growing up. I personally know people that used cannabis as teenagers (and still do to this day) that I would consider to be geniuses. Marijuana does not make a person dumber, and in fact, can boost creativity. There are countless testimonies from smart, successful people out there attesting to how marijuana has improved their lives, and not that marijuana has hurt their brains. Reefer madness debunked by science, again.