From your link:
‘the study doesn’t prove causality, cautions Dr. Diana Martinez, a psychiatrist and addiction researcher at Columbia University. “You can’t say that cannabis causes psychosis,” she says. “It’s simply not supported by the data,” she says.
‘Lisdahl agrees. In order to show causality, one would have to follow people over time — before they started using weed to years later when they have their psychotic episodes, she says. “You need twins in the studies, you need genetic information,” among all other kinds of data, she says.’
Would you want a marijuana user—from youth—on your jury?