The four are these: an inherited biological disposition, copious drug exposure, particularly during adolescence, and a catalyzing environment. It’s not necessary to have all four, but once some threshold is reached, it’s like breaching a dam—virtually impossible to rebuild. So, with enough exposure to any addictive drug, any one of us will develop the hallmarks of addiction: tolerance, dependence, and craving. But if the biological predisposition is very high, or use starts during adolescence, or certain risk factors are present, less exposure will do the trick.
