Nvironmental factors of substance abuse

Heroin abuse disorder and the environmental factors.
Most of this can be found on the web but they must be credible sources.
the questions must be addressed in a essay form.
1) What are some of the environmental influences that have been investigated in this disorder (substance abuse) What is the nature of these environmental influences -how do they work?
2) Which of these influences do researchers feel is most important?
3) Are the environmental influences thought to have more of an impact in this disorder than biological influences or is genetics and biology most important?
4) How might environment interact with a persons biological systems in influencing this disorder?
5) Can this disorder be effectively treated using only one approach or is it more effective to combine approaches (including medical approaches)