Chances are that your son is addicted to pot and will use it again. Unfortunately, sometimes pot is laced with other things like LSD, meth
, cocaine, etc. There is no saying whether he will crave the meth again (which is a highly addictive substance). Since he used it for so long, it is possible. If he has been clean for a while now, he should be safe from the toxic effects of the laced pot. However he will need long term help for dealing with the addiction he certainly has. I suggest you check the NIH drug addiction
website for resources that may help your son. The address is drugabuse.gov. Good luck.