Originally Posted by
cynical one 
IMO, the drugs enhance the preexisting personality disorder.
I remember a saying about the truth coming out when you're drunk. What I've seen in myself and others when under the influence is that the true
personality comes out. I remember a time when I had all sorts of unresolved sadness in my life but always put on a good front. I got drunk and spent the night crying; the "truth" finally came out. My inhibitions were gone.
Our brains have evolved from cave man days in that we developed a conscience, but we never lost our survival instinct that screams "me, me, ME!" Substance abuse hijacks the brain, the conscience is overpowered, and it's all about "me" again.