Thanks for the responses, they are all very good. This is something I have put a lot of thought into and I still don't have the answers. I will read up on the suggested link about "Under the Influence".
I can say from personal experience that I used to drink on the weekends and when I worked 40 hours it wasn't a problem, but then when I was forced to work 60 and sometimes even 72 hours a week my drinking on the weekend skyrocketed. When I went back to 40 hours at work my weekend drinking went back to a normal. I think stress made me drink more, plain and simple. Although I don't completely understand the dynamic. Too much stress can probably be equated to pain in the mind, so I would say that pain is the most probable culprit of a person becoming addicted. No matter what the variables are, genetics, environment, upbringing.....mental pain seems to be available to any scenario.
So what causes addiction? I have no idea. People are so very different. I really need to figure this out.
My sister goes to the methadone clinic 6 days a week. She is an addict. I want to help her but she is so messed up from the past drug use and possibly the current drug use. I don't know how to help her. If I can figure this cause of addiction thing out, I think I can save my sister before she kills herself. I have tried everything I can think of and helped her in every way I can but she just gets worse. Years ago, the tough love thing pushed her way farther into drug use and today being nice to her only works if I give her money.
Any direction here would be helpful.