For some families, marijuana, which was once the root of all their battles, has brought them closer together. Instead of parental warnings and punishment, there are questions about how to light a water pipe; instead of the Grateful Dead, there are recipes for low-sodium brownies.

But for parents, there is also the knowledge that they are putting their children at risk of arrest.

“I was very uncomfortable getting my son involved,” said the father of Alex, 21. The father, who is 54, started using marijuana to relieve his pain from degenerative disc disease. He soon discovered that Alex, who lives in Minnesota a few miles away, had access to better marijuana than he did.