To understand why alcoholism is a disease, it is important to know about the neurological effects of alcohol on the brain. Simply put, heavy drinking over time causes changes in neurotransmitter activity that the brain must adapt to. In people physically predisposed to alcoholism, this adaptation eventually turns into a fixed craving as the body finds it cannot live without the effects of alcohol. Something that started out voluntarily and enjoyable turns into something more serious–a physical dependence that can cause horrible withdrawel symptoms. This explains why alcoholics cannot just quit drinking like their nonaddicted counterparts can. Thus, it is not the behavior of drinking that is defined as an illness. It is only when the craving to drink becomes involuntary that alcoholism can be thought of as a disease.