ScubLdy is absolutely right. Addiction is the problem no matter the substance/action. One of the saddest things I ever saw was a documentary on sex addicts. Yeah, laugh laugh--right? Wrong! Those people were truly pathetic and due to society's attitude towards sex (more more more!!!) people dont' take an addiction like that seriously. The sex addicts were jeopardizing their lives and the lives of others not to mention constantly reinforcing feelings of worthlessness. It was truly sad.
In my previous post I only put forth the biological mechanism of introducing substances like heroin/meth/coke/alcohol into the body, nothing more.