Reliance on addictive substances is a negative coping mechanism.

Yes, drugs are indeed a negative coping mechanism. Psychologists believe that the need to abuse narcotic drugs is a result of an underlying problem that needs to be unearthed and expressed openly. People who are experiencing drug abuse often are mentally and emotionally unstable and should seek professional help. They either end up hurting themselves or other people, sometimes without the knowledge of it.  

Those recovering from the abuse attend group sessions where they openly share experiences with people who have also undergone the same experience.

They probably don't understand either 1. what the nightmare is about or 2. his anxiety and stress