Did you read the actual study OP? Moderate users of cannabis had less bone fractures than the control group.

And for the "heavy" users, 95 out of the 114 test subjects also abused heroin or other illegal opioids.

The definition of a heavy user was the equivalent of smoking weed 5 times a day, every day for 25 years.

Shouldn't you change the title to "Moderate cannabis use strengthens bones while herion makes them weaker"???