The main acute effects of ethanol are on the nervous system, causing characteristic changes in behaviour and judgement. There are particular issues with regard to driving, with different countries setting various ‘safe’ limits for blood-ethanol concentration. Very high blood-ethanol concentrations can be fatal.
Hangovers are unpleasant and are poorly understood. Various mechanisms have been proposed including direct effects of ethanol on organs, ethanol withdrawal, accumulation of acetaldehyde and the effects of other chemicals present in alcoholic drinks. Many treatments are in common usage but there is little evidence of any particular intervention being beneficial.
Alcoholic liver disease results from excessive drinking and includes fatty liver (which is the early reversible stage) and the more serious alcohol-induced hepatitis and cirrhosis.
Excessive drinking can also lead to nervous-system damage resulting in dementia, and shrinking of central nervous system tissue.
Fetal alcohol syndrome can result from maternal alcohol consumption during pregnancy. It involves disruption of fetal development causing CNS abnormalities, growth retardation and characteristic facial features.
Treatment of liver disorders is difficult other than by abstinence.