Immediate Effects

Unlike food, alcohol needs not be digested. It is quickly absorbed into your body. It produces an immediate tranquillizing effect, followed by disinhibition. When you drink more, alcohol impairs your brain function and your self-control ability. Further drinking of alcohol suppresses brain function and can be lethal in some cases.

Some immediate effects to your brain and behaviour
Tranquillizing Disinhibition Concentration impairment Judgement impairment Slowing reflexes Slowing reaction time Coordination impairment	Headache Slurring of speech Drowsiness Altered emotions Vomiting Breathing difficulties Unconsciousness Coma

Although people react to alcohol differently due to different gender, age, ethnicity, weight, physical fitness, amount of food in their stomach, amount and speed of alcohol being consumed, use of drugs or medication, and family history of alcohol problems, a general principle holds valid. That is, the more alcohol you drink in a shorter period of time, the larger the immediate effect on brain and behaviour you are to get.
 

Immediate alcohol-related harm

Your cognitive performance decreases progressively with alcohol intake, so each additional drink further increases your chance of suffering from the harm below:

You may also experience a hangover, typically in the morning after a night of drinking. It is characterised by headache, nausea, sensitivity to light and noise, tiredness, diarrhea and thirst. In addition to the physical symptoms, a hangover may also include heightened feelings of depression and anxiety.
 

Whats more?

Apart from your own health, people around you may also become victims of alcohol-related aggression or road traffic accidents due to drink-driving.

So if you do not drink at all, do not start drinking.
If you choose to drink alcoholic beverages, limit your drink to minimise alcohol-related harm.