The addict's reliance on the drug to reawaken her dulled feelings is no adolescent caprice. The dullness is itself a consequence of an emotional malfunction not of her making
 the internal shutdown of vulnerability. Vulnerability is our susceptibility to be wounded. This fragility is part of our nature and cannot be escaped. The best the brain can do is to shut down conscious awareness of it when pain becomes so vast or unbearable that it threatens our ability to function. The automatic repression of painful emotion is a helpful child's prime defence mechanism and can enable the child to endure trauma otherwise be catastrophic. The unfortunate consequence is a wholesale dulling of emotional awareness.
Gabor Maté, In the Realm of Hungry Ghosts: Close Encounters with Addiction