Low doses of alcohol (one 360 ml (13 imp fl oz; 12 US fl oz) beer ) appear to increase total sleep time and reduce awakening during the night. The sleep-promoting benefits of alcohol dissipate at moderate and higher doses of alcohol.  Previous experience with alcohol also influences the extent to which alcohol positively or negatively affects sleep. Under free-choice conditions, in which subjects chose between drinking alcohol or water, inexperienced drinkers were sedated while experienced drinkers were stimulated following alcohol consumption.  In insomniacs , moderate doses of alcohol improve sleep maintenance. 
So if alcohol is a natural product, why do we need to be concerned about drinking it? When people drink, alcohol is absorbed into their bloodstream. From there, it affects the central nervous system (the brain and spinal cord), which controls virtually all body functions. Alcohol is a depressant, which means it slows the function of the central nervous system. That's why drinking small amounts of alcohol reduces anxiety. Alcohol actually blocks some of the messages trying to get to the brain. This alters your perceptions, your emotions, and even your movements, vision, and hearing. More alcohol causes greater changes in the brain, resulting in intoxication. People who have overused alcohol may stagger, lose their coordination, and slur their speech. They will probably be confused and disoriented. Intoxication can make people very friendly and talkative or very aggressive and angry. Reaction times are slowed dramatically. People who are intoxicated may think they're moving properly, when they're not. They may act totally out of character. The following is a summary of the effects that alcohol has on your body.
Alcohol abuse and addiction are serious medical conditions that require treatment by chemical dependency specialists. Abruptly stopping alcohol consumption after extended use can result in serious medical complications, including death. Detoxification from alcohol dependence should not be attempted at home or without direction and supervision from a medical doctor. If you or your loved one are concerned you may be experiencing symptoms of alcohol withdrawal and are not under a physician’s care, call 911 for emergency assistance.