As Minnesota considers legalizing marijuana, what does research say about the risks?
February 6, 2023
The University of Minnesota's vaunted twins study had as good a shot as any to sort out the murky health effects of recreational marijuana.
By factoring out differences in genetics, upbringing and age, the study offered a purer comparison of twins who smoked marijuana vs. siblings who didn't. After comparing 364 sets of identical twins, the U researchers found in 2021 that the marijuana users had lower grades and were less likely to attend college and earn higher incomes.
But the study didn't find the cognitive declines and mental health problems others have ascribed to marijuana. Even twins lead different lives, so it's also possible other influences were at work, said Jonathan Schaefer, a lead author and researcher at the U's Institute of Child Development.