When alcohol is present in the blood stream it directly effects the hypothalamus, possibly damaging it particularly during adolescent years. Alcohol has a profound effect on the frontal lobe- the part of the brain that allows us to analyze and program our behavior. It also allows us to convert experience to memory and is responsible for the formation of our 'self-image'. These processes require a tremendous amount of energy. The depressant nature of alcohol directly lowers the energy center in the brain.
Mental capacity is lost and the ability to recognize the loss.
Adolescence is a time of fluctuating psychological and physical growth. The brain is the only body organ not equipped with pain fibers or the ability to produce new brain cells should they die. Know the facts so when you say 'NO' you know why. The most profound early effects is on the central nervous system. It acts as a sedative, producing relaxation and a sense of well-being.