Ulrich Lanius, a clincial psychologist, researcher, therapist, and writer in Vancouver sent me this:

"The connection between dissocation, depression and addiction is a fascinating one and more likely than not  related to attachment. An article written by Bessel van der Kolk some insight into this:

http://www.cirp.org/library/psych/vanderkolk/

For more intensive reading, Alan Schore describes the effect between attachment and infant trauma and how they lead to traumatic stress syndromes:

http://www.trauma-pages.com/a/schore-2001b.php

There is little doubt that dissociation is in part mediated by an excessive release of endogenous opiates/endorphins. Animal studies that mimic neglect also suggest that animals that have experienced lack of caregiving have fewer opiate receptors. This likely  leads to lack of pleasure and sometimes intolerance of positive emotions, a common phenomenon in human beings that have experienced attachment trauma and who suffer from depression.

Addictions can be seen as an attempt by the addict to make up for impaired functioning of their own opiate system. Except that the pleasure derived is short lasting and commonly leads to negative outcomes in the long run, health or otherwise.

Another exciting development in the research on opiates are the effects of opiate antagonists on immmune system disorders but also potentially positive effects on depression. A review paper can be found here:

www.ldn4cancer.com/techpapers/ldn_for_disease_prevention_quality_of_life.pdf  "

Thanks Ulrich!