Why does pleasure and desire lead to addiction in some people but not others? Mike Williams talks to scientists and former addicts.

What happens when the biochemistry of the brain’s pleasure and reward system goes wrong? How can something that starts off being pleasurable end up making us feel so low? Mike Williams talks to scientists and former addicts to search for some answers to the power of addiction.

(Photo: Collection of different hard drugs heroin, pills, tobacco and alcohol. Credit: Shutterstock)