On the other hand, advances in medicine seem to confirm that addiction is more complicated than that. Many have proposed that it is actually a disease. A disease is a disruption in a part or parts of the body causing them to function incorrectly. Substance abuse is a disease which affects that part of your brain that determines what is necessary for survival. A part of your brain was designed to learn what is necessary for survival and to release pleasurable and rewarding chemicals (already stored in the brain) to let you know that, "This action is good. Do it again." For someone who has become addicted, the brain (an organ) begins to believe that your drug of choice or alcohol is required for survival. Since your drug of choice or alcohol are not necessary for survival, this is known as an "abnormal symptom," and this is why addiction is considered a disease.