Marijuana increases appetite, relieves pain and does not cause cold sweats. If it did result in those symptoms, it would not be moving into a more prominent use for valid medical purposes.
However, all of the side effects you have described are very common with people who are using or abusing amphetamines, and they show up with both casual use or addictive consumption.
I think you and your grandson's parents need to either confront him about his behavior and get him help. Iif you are unable or unwilling to do that, all you have to do is call the cops on him. That will pretty much have the same effect, albeit it does bring criminal charges along with it.