regulate alcohol intake. Physical dependence is an adaptive state manifested by intense physical disturbances that occur when drinking is discontinued. Dependence results from the adaptation of central nervous system structures and functions (and probably those of other organs as well) to the presence of alcohol. Tolerance refers to the diminished effect of a given amount of alcohol that tends to develop with regular use. In spite of this diminished effect, however, many aspects of brain functioning are impaired, and vital organs may be damaged.
Alcohol is involved in over 100,000 deaths annually in the United States (from motor vehicle crashes, unintentional injuries, suicides, and the medical effects of alcohol dependence) and plays a major role in numerous medical and social problems (NIAAA, 1991; IOM, 1989a). Motor vehicle crashes are the nation's leading cause of injury deaths, and approximately half of all crash fatalities are alcohol related (DHHS, 1990; IOM, 1985). Such crashes, of course, leave many others with permanent disabilities, including head injuries. About half of all fire deaths are associated with alcohol use, 20 to 77 percent of fatal falls involve alcohol, and 25 to 50 percent of drowning deaths may be the result of drinking (IOM, 1989a). Alcohol is estimated to be involved in approximately 30 percent of all suicides and plays a particularly significant role in adolescent suicide and in suicide with the use of firearms, and it is also highly associated with homicides (NIAAA, 1991).