Negative emotions, like depression or anxiety, have been shown to affect our immune system. Stress impedes wound healing.
How do you think your body and mind would respond if you were surrounded by psychologists, psychiatrists, or drug and alcohol counselors who subscribed to the belief that "once an alcoholic or addict, always an alcoholic or addict" and who believed that your current stay in rehab would be one of many?
If you can stop using substance or stop your addictive behavior for extended periods of time without craving, you are not dependent. You are dependent only if you can't stop without physical or psychological distress (you have unpleasant physical and/or psychological withdrawal symptoms) or if you stop and then relapse.
Depression can be due to a low endocrine function, nutritional deficiencies, blood sugar problems, food allergies, or systemic yeast infection. Depression can also result from medical illnesses such as stroke, heart attack, cancer, Parkinson's disease, and hormonal disorder. It can also be caused by a serious loss, a difficult relationship, a financial problem, or any stressful, unwelcome life change.