This study was done with biofeedback rather than BWE but the implications are the same.
The participants received 15 sessions of 15-30 minutes of Alpha/Theta brain training.
The control group, who received traditional therapy showed the expected increase of Beta Endorphins (a protein released by stress in response to pain) during their therapy whereas the group receiving Brainwave training had no such increase and also showed significant reductions in feelings of depression.
Follow ups done with the participants 13 months later showed a prevention of relapse into alcoholism. IE: Over a year after Alpha/Theta brainwave training these study participants were still in control and no longer alcoholics.