A healthy nervous system in a healthy environment (with attuned caregivers and limited traumatic experience) will equipt a person with the neural pathways (and associated beliefs and behaviors) to regulate their nervous system.
In compromised development, either through lack of attunement or childhood / early trauma folks don't have the ability to automatically regulate and they are in a constant state of fight / flight. The dopamine helps to deal with this temporarily.
Psychedelics, some therapy, and sometimes near death / mystical experiences (moments of clarity) can offer a window of opportunity in which the ego loosens its grip enough for the nervous system to relax and for the subconscious material (traumas) to come to the surface and be released with the accompanying rewiring of the fight / flight response.
When one experiences reality from an undefended state it is generally such a pleasurable, rich experience that the desire to use other mechanisms of self-soothing organically fade away and the cognition and behavior reorient to healthier more nourishing alternatives.
These experiences and therapy combined with a healthy environment and relationships that support the honest expression of emotion (ie, not co-dependent) can rapidly support healing.
The basic idea is that traumas are trapped in the somatic system and that altered states of consciousness combined with the right context can allow for an unfolding and healing of the underlying issues.
Depending on the underlying issue and severity of the defense structures folks may find help with various psychedelic substance from MDMA, Iboga, LSD, Mushroom or Ayahuasca.
We also have seen great result using Holotropic Breathwork which was developed as a legal alternative to LSD Psychotherapy.
This is essentially the same process I used to heal from bipolar, as I began to see bipolar as an "addiction" to states of depression and mania as a protective, adaptive response.
It's also the process I now use with my clients and the underlying philosophy that I bring to the communities that support.
If anyone is interested, there is a new book out (published anonymously) that documents accounts of a number of people who have been helped by an underground MDMA therapy practice. (Not specific to substance addiction, but includes some accounts.)