Comment by skohan

In another life I was a research assistant in a lab studying drug addiction, and our operating assumption was that - like any other system in the brain - it's not as simple as saying "neurotransmitter X causes Y". But there does seem to be an awful lot of evidence (or at least there was a lot of evidence cerca 2008-2009) to suggest that dopamine is heavily involved in motivation and habit formation, which are easily linked to addiction.