People who are depressed and people who are addicted have something in common, according to Dr. Eric Nestler. He says that both groups tend to be weak in their ability to feel pleasure and satisfaction.
He advocates putting emphasis on the "reward regions" of the brain which, in the case of the addict, research suggests have been altered after long-term drug use. He says that this alteration in the brain brings about the behavior patterns typical of addiction.
He believes it's possible to modify genes so that "reward" is intensified, and that this may help some people break free from both depression and addiction.
"Eric J. Nestler, MD, PhD, is the Nash Family Professor of Neuroscience at the Mount Sinai School of Medicine in New York, where he serves as Chair of the Department of Neuroscience and Director of the Mount Sinai Brain Institute. The goal of Dr. Nestler’s research is to better understand the molecular mechanisms of addiction and depression based on work in animal models, and to use this information to develop improved treatments of these disorders."
http://blogs.psychcentral.com/therapy-soup/2010/04/addiction-and-depression-research-therapy-soup-talks-with-dr-eric-nestler