> "I think the evidence is pretty good that there is an increased risk," Reznik said, but the association does not prove a cause-and-effect relationship. The a

> "I think the evidence is pretty good that there is an increased risk," Reznik said, but the association does not prove a cause-and-effect relationship. The article basically acknowledges this. They have a ton of data - over a million surgeries and 22K marijuana users. However, there's no proof of cause-and-effect because they have no way of knowing if it's correlation of causation. All they can say for sure is that these patients are at increased risk.