what are the main differences between the psychological and physiological dependence on alcohol and/or a drug?
What is the difference between psychological and physical dependence? This is a very complicated (although simple) question. Physical dependence on a drug (recreational or not) means the body gets used to the drug, it needs more and more of it to accomplish the same effect. Eventually, the drug is merely used to counteract the withdrawal symptoms that appear when no drugs are being taken.
Mental/psychological dependence means somebody can't feel comfortable/relaxed anymore without the drug. This mechanism has nothing to do with the body, but with feelings of fear, pain, shame, guilt, loneliness and so on. The drug is used to forget problems which should be solved.