Extend of Problem Should They Be "Diseases of the Brain"?

There are people in the world who are addicted to drugs and alcohol. Some will believe that they are addicted to it and it is their fault, while others believe it is a disease in the brain.
I personally believe that drugs and alcohol are NOT diseases of the brain. I believe that when people get depressed they will take certain steps to get out of their depression. Some will eat others will sleep and there are people in the world who will turn to drugs and alcohol to get rid of the depression. Most likely for those individuals, it will become an addiction unless they get help. But I never once thought that addiction was a disease of the brain.
Depression is different. Depression is a mental disorder in which many people suffer from. Besides alcoholism and drug addiction, depression is a disease of the brain. There is a chemical imbalance and for many people they have to seek medication. I know someone who suffers from major depression and he would cut himself over and over again on the arm. When he thought enough was enough, he seek helped and was put on medicine and now sees a therapist once a week and he has not cut himself in almost 6 months. Depression hurts a lot of people and it can get dangerous.