there are some addicting drugs out there... Like coke, amphetemines, heroine, alchohol, caffeine, barbituates, nicotine etc. and they all have physical and mental withdrawl effects. and afterall, the only thing that makes something addictive is it having withdrawl.

but there are absolutely no physical withdrawl effects from thc or any other cannabinoids. there can be psychological withdrawls, but they are not caused by pot, they are simply caused by you thinking that you have them