Chronic use of alcohol leads to increased tolerance and both psychological and physical addiction, all signs of your nervous system getting used to alcohol. Alcoholism is usually taken to refer to a psychological addiction to alcohol. The effects of alcohol on the nervous system are not known in detail; unlike most other intoxicants, alcohol does not influence a specific location in the brain.
In addition to its intoxicating effects, alcohol also has psychological effects, which are experienced as pleasure and which may cause you to want to drink again and again. These effects may lead to a tendency to drink more and more as your brain adapts to alcohol, and thus promote the development of alcohol addiction.
A psychological dependency on alcohol is a form of alcohol addiction. An alcoholic is a person who is psychologically addicted to alcohol or fulfils certain diagnostic criteria. (Alcohol addiction has been defined in the diagnostic criteria of e.g. DSM-IV and ICD 10.)Psychological dependency is characterised by a craving to drink, a compulsion for consuming alcohol, and an inability to refrain from drinking. High-scale consumption brings about increased tolerance and physical dependency, which manifests in withdrawal symptoms when drinking is stopped. Withdrawal involves sickness and feeling low, which may also promote the use of alcohol.
Inability to refrain from drinking often leads to a relapse - starting drinking again. Stress is apparently one of the central causes of relapse. Alcohol addiction is also characterised by the overall decline of health and social well-being.
Continuous high-scale consumption of alcohol leads to physical addiction. A physical dependency usually only becomes apparent when the individual experiences withdrawal symptoms after he stops drinking and the alcohol begins to leave his system. Physical addiction and withdrawal symptoms are only one manifestation of alcoholism.
For a physical addiction to develop, the individual needs to expose himself to the effects of alcohol continuously. According to certain findings, daily binges that do not elevate the blood alcohol content above one per mil, do not lead to a physical addiction. It also appears that stopping drinking for several days decreases the likelihood of physical addiction, as breaks from drinking give the incipient addiction time to dissolve.
The nervous system adapts to the depressant effects of alcohol, so when alcohol is no longer present, the nervous system becomes overstimulated and causes symptoms of withdrawal. These symptoms begin to appear when the blood alcohol content drops to close to zero. Usually the symptoms manifest themselves 12–48 hours after alcohol was consumed, and their severity and onset depend on how much alcohol was consumed.
Even a hangover, following a single binge, is essentially a state of withdrawal. When drinking comes to an end after long-term, high-scale drinking spree, the symptoms are stronger and it takes longer to recover from them. The most serious form of alcohol withdrawal is delirium tremens.
National Institute for Health and Welfare