When dealing with addictive behaviors, which can include substances or simply a hobby taken too far so as to be detrimental in some way, one should not focus on the addiction itself. One depressed person may drink, another may eat, another may shop, another work. All of these are benign if kept in balance, but anything can be abused. We need to look at what has made the person depressed in the first place. No, it's not a chemical imbalance. A chemical imbalance in the brain is the result of the problem, not the cause. Everyone has a unique life with unique difficulties and we all have much suffering to learn from. And that's the point, to learn from suffering rather than run away from it.