Addiction may stem from 3 components: biological, social, and psychological. If you have a history of addiction in your family you may be genetically predisposed (just like if there is a history of diabetes, heart disease, cancer etc..). If you grow up in area where drugs are predominant and everyone uses chances are you will use and after time may cross the line into addiction. If you have had psychological trauma and did not cope in a healthy way and turned to drugs and alcohol, you will probably turn to these substances to cope with other events in life, and thus become psychologically dependent. I believe if anyone uses long enough they have the ability to become physically addicted and cross the line from social user to addict. If you have one of the 3 components it may take longer to cross the line and if you have all 3 it speeds up the process.