Both. There is a genetic component according to c.Robert cloninger's studies of scandanavian twins adopted at birth, but he noted that majority of the etiology is "non-specific". 12 steps are best treatment strategy developed so far. If you have trouble with the spiritual aspect, try holotropic breathwork first.
Tomato or Tomato. Drug abuse and excessive drinking are both physical and psychological problems. If one considers the biological origins of psychological problems, then they boil down to purely physical problems. Semantics aside, drug abuse and excessive drinking are serious problems with high rates of morbidity and mortality. Treatment is available for both. Don't wait see your md today and ask for help.