All the drug abusers I know (and there are far too many) started in order to turn off reality and "kill their emotional pain". The only time they feel good is when they are high. That is followed by a low equal to the high so they go for some more to ease the pain or for something harder.

This is like the difference between pigging out on a whole pizza because you are down and eating 10,000 calories every day to numb yourself. Actually a better example is the difference between enjoying a glass of wine to relax and downing two bottles of vodka at work just to get through the day.