I suppose when a youngster is repetitively beaten as a child (as was noted with Tom) it may lead to an under-active dopamine mechanism. Later in life, one such person (as Tom) may be introduced to cocaine and such stimuli... his brains "reward center" makes him feel THIS is normal. A dangerous pathway (in multiple senses) may have been set. IMO, addictions can be a curse. In the past when I volunteered with an organization that helped the needy (St Vincent de Paul Society) I often witnessed the effects and outcomes of addictions. It's rare any become (high) functional addicts. If one thinks they are, typically they die.