Individuals with an alcohol use disorder will often complain of difficulty with interpersonal relationships, problems at work or school, and legal problems. Additionally, people may complain of irritability and insomnia. Alcohol abuse is also an important cause of chronic fatigue.

Signs of alcohol abuse are related to alcohol's effects on organ systems. However, while these findings are often present, they are not necessary to make a diagnosis of alcohol abuse. Signs of alcohol abuse show its drastic effects on the central nervous system, including inebriation and poor judgment; chronic anxiety, irritability, and insomnia. Alcohol's effects on the liver include elevated liver function tests (classically AST is at least twice as high as ALT). Prolonged use leads to cirrhosis and liver failure. With cirrhosis, patients develop an inability to process hormones and toxins. The skin of a patient with alcoholic cirrhosis can feature cherry angiomas, palmar erythema and — in acute liver failure — jaundice and ascites. The derangements of the endocrine system lead to the enlargement of the male breasts. The inability to process toxins leads to liver disease, such as hepatic encephalopathy.

Alcohol abuse can result in brain damage which causes impairments in executive functioning such as impairments to working memory, visuospatial skills, and can cause an abnormal personality as well as affective disorders to develop. Binge drinking is associated with individuals reporting fair to poor health compared to non-binge drinking individuals and which may progressively worsen over time. Alcohol also causes impairment in a person's critical thinking. A person's ability to reason in stressful situations is compromised, and they seem very inattentive to what is going on around them. Social skills are significantly impaired in people suffering from alcoholism due to the neurotoxic effects of alcohol on the brain, especially the prefrontal cortex area of the brain. The social skills that are impaired by alcohol abuse include impairments in perceiving facial emotions, difficulty with perceiving vocal emotions and theory of mind deficits; the ability to understand humour is also impaired in alcohol abusers. Adolescent binge drinkers are most sensitive to damaging neurocognitive functions especially executive functions and memory. People who abuse alcohol are less likely to survive critical illness with a higher risk for having sepsis and were more likely to die during hospitalization.

Alcohol (also known as ethanol) has a number of effects on health. Short-term effects of alcohol consumption include intoxication and dehydration. Long-term effects of alcohol consumption include changes in the metabolism of the liver and brain and alcoholism. Alcohol intoxication affects the brain, causing slurred speech, clumsiness, and delayed reflexes. Alcohol stimulates insulin production, which speeds up glucose metabolism and can result in low blood sugar, causing irritability and possibly death for diabetics. A 2014 World Health Organization report found that harmful alcohol consumption caused about 3.3 million deaths annually worldwide.

However, some effects of alcohol consumption are beneficial. Although even moderate alcohol consumption increased the risk of death in younger people, it has been shown to "decrease" the risk of death for individuals ages 55+ (due to decreased risk of ischemic heart disease).

The median lethal dose of alcohol in test animals is a blood alcohol content of 0.45%. This is about six times the level of ordinary intoxication (0.08%), but vomiting or unconsciousness may occur much sooner in people who have a low tolerance for alcohol. The high tolerance of chronic heavy drinkers may allow some of them to remain conscious at levels above 0.40%, although serious health hazards are incurred at this level.

Alcohol also limits the production of vasopressin (ADH) from the hypothalamus and the secretion of this hormone from the posterior pituitary gland. This is what causes severe dehydration when alcohol is consumed in large amounts. It also causes a high concentration of water in the urine and vomit and the intense thirst that goes along with a hangover.

Stress, hangovers, and the oral contraceptive pill may increase the desire for alcohol because these things will lower the level of testosterone and alcohol will acutely elevate it. Tobacco has the same effect of increasing the craving for alcohol.

Alcohol abuse among pregnant women causes their baby to develop fetal alcohol syndrome. Fetal alcohol syndrome is the pattern of physical abnormalities and the impairment of mental development which is seen with increasing frequency among children with alcoholic mothers. Alcohol exposure in a developing fetus can result in slowed development of the fetal brain, resulting in severe retardation or death. Surviving infants may suffer severe abnormalities such as abnormal eyes, fissures, lips and incomplete cerebella. Some infants may develop lung disease. It is even possible that the baby throughout pregnancy will develop heart defects such as ventricular septal defect or atrial septal defect. Experts suggest that pregnant women take no more than one unit of alcohol per day. However, other organizations advise complete abstinence from alcohol while pregnant.

From the ICD-9 database:

- A chronic disease in which a person craves drinks that contain alcohol and is unable to control his or her drinking. A person with this disease also needs to drink greater amounts to get the same effect and has withdrawal symptoms after stopping alcohol use. Alcoholism affects physical and mental health, and can cause problems with family, friends, and work.

- A disorder characterized by a pathological pattern of alcohol use that causes a serious impairment in social or occupational functioning.

- A primary, chronic disease with genetic, psychosocial, and environmental factors influencing its development and manifestations. The disease is often progressive and fatal. It is characterized by impaired control over drinking, preoccupation with the drug alcohol, use of alcohol despite adverse consequences, and distortions in thinking, most notably denial. Each of these symptoms may be continuous or periodic. (morse & flavin for the joint commission of the national council on alcoholism and drug dependence and the american society of addiction medicine to study the definition and criteria for the diagnosis of alcoholism: in jama 1992;268:1012-4)

- For most adults, moderate alcohol use is probably not harmful. However, about 18 million adult Americans are alcoholics or have alcohol problems. Alcoholism is a disease with four main features:

- craving - a strong need to drink

- loss of control - not being able to stop drinking once you've started

- physical dependence - withdrawal symptoms, such as nausea, sweating, or shakiness when you don't drink

- tolerance - the need to drink greater amounts of alcohol to feel the same effect

- Temporary mental disturbance marked by muscle incoordination and paresis as the result of excessive alcohol ingestion.

Warning signs of alcoholism include the consumption of increasing amounts of alcohol and frequent intoxication, preoccupation with drinking to the exclusion of other activities, promises to quit drinking and failure to keep those promises, the inability to remember what was said or done while drinking (colloquially known as "blackouts"), personality changes associated with drinking, denial or the making of excuses for drinking, the refusal to admit excessive drinking, dysfunction or other problems at work or school, the loss of interest in personal appearance or hygiene, marital and economic problems, and the complaint of poor health, with loss of appetite, respiratory infections, or increased anxiety.

Alcoholism, also known as alcohol use disorder (AUD), is a broad term for any drinking of alcohol that results in mental or physical health problems. The disorder was previously divided into two types: alcohol abuse and alcohol dependence. In a medical context, alcoholism is said to exist when two or more of the following conditions is present: a person drinks large amounts over a long time period, has difficulty cutting down, acquiring and drinking alcohol takes up a great deal of time, alcohol is strongly desired, usage results in not fulfilling responsibilities, usage results in social problems, usage results in health problems, usage results in risky situations, withdrawal occurs when stopping, and alcohol tolerance has occurred with use. Risky situations include drinking and driving or having unsafe sex, among other things. Alcohol use can affect all parts of the body, but it particularly affects the brain, heart, liver, pancreas, and immune system. This can result in mental illness, Wernicke–Korsakoff syndrome, an irregular heartbeat, cirrhosis of the liver, and an increase in the risk of cancer, among other diseases. Drinking during pregnancy can cause damage to the baby resulting in fetal alcohol spectrum disorders. Women are generally more sensitive then men to the harmful physical and mental effects of alcohol.

Environmental factors and genetics are two components that are associated with alcoholism, with about half the risk attributed to each . A person with a parent or sibling with alcoholism is three to four times more likely to become an alcoholic themselves. Environmental factors include social, cultural, and behavioral influences. High stress levels, anxiety, as well as inexpensive cost and easy accessibility to alcohol increase the risk. People may continue to drink partly to prevent or improve symptoms of withdrawal. After a person stops drinking alcohol, they may experience a low level of withdrawal lasting for months. Medically, alcoholism is considered both a physical and mental illness. Questionnaires and certain blood tests may both detect people with possible alcoholism. Further information is then collected to confirm the diagnosis.

Prevention of alcoholism may be attempted by regulating and limiting the sale of alcohol, taxing alcohol to increase its cost, and providing inexpensive treatment. Treatment may take several steps. Due to medical problems that can occur during withdrawal, alcohol detoxification should be carefully controlled. One common method involves the use of benzodiazepine medications, such as diazepam. This can be either given while admitted to a health care institution or occasionally while a person remains in the community with close supervision. Mental illness or other addictions may complicate treatment. After detoxification support such as group therapy or support groups are used to help keep a person from returning to drinking. One commonly used form of support is the group Alcoholics Anonymous. The medications acamprosate, disulfiram, or naltrexone may also be used to help prevent further drinking.

The World Health Organization estimates that as of 2010 there were 208 million people with alcoholism worldwide (4.1% of the population over 15 years of age). In the United States about 17 million (7%) of adults and 0.7 million (2.8%) of those age 12 to 17 years of age are affected. It is more common among males and young adults, becoming less common in middle and old age. It is the least common in Africa at 1.1% and has the highest rates in Eastern Europe at 11%. Alcoholism directly resulted in 139,000 deaths in 2013, up from 112,000 deaths in 1990. A total of 3.3 million deaths (5.9% of all deaths) are believed to be due to alcohol. It often reduces a person's life expectancy by around ten years. In the United States it resulted in economic costs of $224 billion USD in 2006. Many terms, some insulting and others informal, have been used to refer to people affected by alcoholism; the expressions include tippler, drunkard, dipsomaniac, and souse. In 1979, the World Health Organization discouraged the use of "alcoholism" due to its inexact meaning, preferring "alcohol dependence syndrome".

College drinking is the consumption of alcohol by students on the campus of any college or university. The age at which it is legal to drink varies by country and affects whether college drinking is considered illegal (e.g., as in the United States, where it is illegal for those under the age of 21 to drink).

According to the DSM-IV criteria for alcohol dependence, at least three out of seven of the following criteria must be manifest during a 12-month period:

- Tolerance

- Withdrawal symptoms or clinically defined alcohol withdrawal syndrome

- Use in larger amounts or for longer periods than intended

- Persistent desire or unsuccessful efforts to cut down on alcohol use

- Time is spent obtaining alcohol or recovering from effects

- Social, occupational and recreational pursuits are given up or reduced because of alcohol use

- Use is continued despite knowledge of alcohol-related harm (physical or psychological)

Alcohol is a liquid form substance which contains ethyl alcohol (also known formally as ethanol) that can cause harm and even damage to a persons DNA. "Alcohol consumption is recognized worldwide as a leading risk factor for disease, disability, and death." and is rated as the most used and abused substance by adolescences. Adolescence is a transitional stage of physical and psychological changes, usually a time in a person life in which they go through puberty. Combining these transitional stages and the intake of alcohol, can leave a number of consequences for an adolescent.

Binge drinking, or heavy episodic drinking, is a modern epithet for drinking alcoholic beverages with an intention of becoming intoxicated by heavy consumption of alcohol over a short period of time.

Binge drinking is a style of drinking that is popular in several countries worldwide, and overlaps somewhat with social drinking since it is often done in groups. The degree of intoxication, however, varies between and within various cultures that engage in this practice. A binge on alcohol can occur over hours, last up to several days, or in the event of extended abuse, even weeks. Due to the long-term effects of alcohol misuse, binge drinking is considered to be a major public health issue.

Binge drinking is associated with a profound social harm, economic costs as well as increased disease burden. Binge drinking is more common in males, during adolescence and young adulthood. Heavy regular binge drinking is associated with adverse effects on neurologic, cardiac, gastrointestinal, hematologic, immune, musculoskeletal organ systems as well as increasing the risk of alcohol induced psychiatric disorders. A US-based review of the literature found that up to one-third of adolescents binge-drink, with six percent reaching the threshold of having an alcohol-related substance use disorder. Approximately one in 25 women binge-drinks during pregnancy, which can lead to fetal alcohol syndrome and fetal alcohol spectrum disorders. Binge drinking during adolescence is associated with traffic accidents and other types of accidents, violent behavior as well as suicide. The more often a child or adolescent binge drinks and the younger they are the more likely that they will develop an alcohol use disorder including alcoholism. A large number of adolescents who binge-drink also consume other psychotropic substances.

The long-term effects of alcohol (also known formally as ethanol) consumption range from cardioprotective health benefits for low to moderate alcohol consumption in industrialized societies with higher rates of cardiovascular disease to severe detrimental effects in cases of chronic alcohol abuse. Health effects associated with alcohol intake in large amounts include an increased risk of alcoholism, malnutrition, chronic pancreatitis, ], and cancer. In addition, damage to the central nervous system and peripheral nervous system can occur from chronic alcohol abuse. The long-term use of alcohol is capable of damaging nearly every organ and system in the body. The developing adolescent brain is particularly vulnerable to the toxic effects of alcohol. In addition, the developing fetal brain is also vulnerable, and fetal alcohol spectrum disorders (FASDs) may result if pregnant mothers consume alcohol.

The inverse relation in Western cultures between alcohol consumption and cardiovascular disease has been known for over 100 years. Many physicians do not promote alcohol consumption, however, given the many health concerns associated with it, some suggest that alcohol should be regarded as a recreational drug, and promote exercise and good nutrition to combat cardiovascular disease. Others have argued that the benefits of moderate alcohol consumption may be outweighed by other increased risks, including those of injuries, violence, fetal damage, liver disease, and certain forms of cancer. Alcohol liver disease (ALD) accounted for four fifths of all chronic diseases in Ireland in 2013.

Withdrawal effects and dependence are also almost identical. Alcohol at moderate levels has some positive and negative effects on health. The negative effects include increased risk of liver diseases, oropharyngeal cancer, esophageal cancer and pancreatitis. Conversely moderate intake of alcohol may have some beneficial effects on gastritis and cholelithiasis. Of the total number of deaths and diseases caused by alcohol, most happen to the majority of the population who are moderate drinkers, rather than the heavy drinker minority. Chronic alcohol misuse and abuse has serious effects on physical and mental health. Chronic excess alcohol intake, or alcohol dependence, can lead to a wide range of neuropsychiatric or neurological impairment, cardiovascular disease, liver disease, and malignant neoplasms. The psychiatric disorders which are associated with alcoholism include major depression, dysthymia, mania, hypomania, panic disorder, phobias, generalized anxiety disorder, personality disorders, schizophrenia, suicide, neurologic deficits (e.g. impairments of working memory, emotions, executive functions, visuospatial abilities and gait and balance) and brain damage. Alcohol dependence is associated with hypertension, coronary heart disease, and ischemic stroke, cancer of the respiratory system, and also cancers of the digestive system, liver, breast and ovaries. Heavy drinking is associated with liver disease, such as cirrhosis. Excessive alcohol consumption can have a negative impact on aging.

Recent studies have focused on understanding the mechanisms by which moderate alcohol consumption confers cardiovascular benefit.

Alcohol is a potent neurotoxin. The National Institute on Alcohol Abuse and Alcoholism has found, "Alcoholism may accelerate normal aging or cause premature aging of the brain." Another report by the same agency found, "Chronic alcohol consumption, as well as chronic glucocorticoid exposure, can result in premature and/or exaggerated aging." Specifically, alcohol activates the HPA axis, causing glucocorticoid secretion and thus elevating levels of stress hormones in the body. Chronic exposure to these hormones results in an acceleration of the aging process, which is associated with "gradual, but often dramatic, changes over time in almost every physiological system in the human body. Combined, these changes result in decreased efficiency and resiliency of physiological function." Chronic stress and chronic heavy alcohol use cause a similar premature aging effect, including nerve cell degeneration in the hippocampus.

The impact of alcohol on aging is multifaceted. Evidence shows that alcoholism or chronic alcohol consumption can cause both accelerated (or premature) aging – in which symptoms of aging appear earlier than normal – and exaggerated aging, in which the symptoms appear at the appropriate time but in a more exaggerated form. The effects of alcohol abuse/misuse on the aging process include hypertension, cardiac dysrhythmia, cancers, gastrointestinal disorders, neurocognitive deficits, bone loss, and emotional disturbances especially depression. On the other hand, research also shows that drinking moderate amounts of alcohol may protect healthy adults from developing coronary heart disease. The American Heart Association cautions people not to start drinking, if you are not already drinking.

The short-term effects of alcohol consumption range from a decrease in anxiety and motor skills at lower doses to unconsciousness, anterograde amnesia, and central nervous system depression at higher doses. Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into nearly every cell in the body.

The concentration of alcohol in blood is measured via blood alcohol content (BAC). The amount and circumstances of consumption play a large part in determining the extent of intoxication; for example, eating a heavy meal before alcohol consumption causes alcohol to absorb more slowly. Hydration also plays a role, especially in determining the extent of hangovers. After excessive drinking, unconsciousness can occur and extreme levels of consumption can lead to alcohol poisoning and death (a concentration in the blood stream of 0.40% will kill half of those affected). Alcohol may also cause death indirectly, by asphyxiation from vomit.

Alcohol can greatly exacerbate sleep problems. During abstinence, residual disruptions in sleep regularity and sleep patterns are the greatest predictors of relapse.

Chronic use of alcohol used to induce sleep can lead to insomnia: frequent moving between sleep stages occurs, with awakenings due to headaches and diaphoresis. Stopping chronic alcohol abuse can also lead to profound disturbances of sleep with vivid dreams. Chronic alcohol abuse is associated with NREM stage 3 and 4 sleep as well as suppression of REM sleep and REM sleep fragmentation. During withdrawal REM sleep is typically exaggerated as part of a rebound effect.

Acute alcohol poisoning is a related medical term used to indicate a dangerously high concentration of alcohol in the blood, high enough to induce coma, respiratory depression, or even death. It is considered a medical emergency. The term is mostly used by healthcare providers. Toxicologists use the term "alcohol intoxication" to discriminate between alcohol and other toxins.

The signs and symptoms of acute alcohol poisoning include:

- severe confusion, unpredictable behavior and stupor

- sudden lapses into and out of unconsciousness or semi-consciousness (with later alcoholic amnesia)

- vomiting while unconscious or semi-conscious

- seizures

- respiratory depression (fewer than eight breaths a minute)

- pale, bluish, cold and clammy skin due to insufficient oxygen

Substance abuse, also known as drug abuse, is a patterned use of a drug in which the user consumes the substance in amounts or with methods which are harmful to themselves or others, and is a form of substance-related disorder. Widely differing definitions of drug abuse are used in public health, medical and criminal justice contexts. In some cases criminal or anti-social behavior occurs when the person is under the influence of a drug, and long term personality changes in individuals may occur as well. In addition to possible physical, social, and psychological harm, use of some drugs may also lead to criminal penalties, although these vary widely depending on the local jurisdiction.

Drugs most often associated with this term include: alcohol, cannabis, barbiturates, benzodiazepines, cocaine, methaqualone, opioids and some substituted amphetamines. The exact cause of substance abuse is not clear, with the two predominant theories being: either a genetic disposition which is learned from others, or a habit which if addiction develops, manifests itself as a chronic debilitating disease.

In 2010 about 5% of people (230 million) used an illicit substance. Of these 27 million have high-risk drug use otherwise known as recurrent drug use causing harm to their health, psychological problems, or social problems or puts them at risk of those dangers. In 2015 substance use disorders resulted in 307,400 deaths, up from 165,000 deaths in 1990. Of these, the highest numbers are from alcohol use disorders at 137,500, opioid use disorders at 122,100 deaths, amphetamine use disorders at 12,200 deaths, and cocaine use disorders at 11,100.

Stolle, Sack and Thomasius define binge drinking as episodic excessive drinking. There is currently no worldwide consensus on how many drinks constitute a "binge", but in the United States, the term has been described in academic research to mean consuming five or more standard drinks (male), or four or more drinks (female), over a 2-hour period. In 2015, the US Centers for Disease Control and Prevention, citing the National Institute on Alcohol Abuse and Alcoholism, defines binge drinking as "a pattern of drinking that brings a person’s blood alcohol concentration (BAC) to 0.08 grams percent or above. This typically happens when men consume 5 or more drinks, and when women consume 4 or more drinks, in about 2 hours." and estimated that about 16% of American adults met these binge drinking criteria four times per month. One 2001 definition from the publication "Psychology of Addictive Behavior" states that 5 drinks for men and 4 drinks for women must be consumed on one occasion at least once in a two-week period for it to be classed as binge drinking. This is colloquially known as the "5/4 definition", and depending on the source, the timeframe can vary. In the United Kingdom, binge drinking is defined by one academic publication as drinking more than twice the daily limit, that is, drinking eight units or more for men or six units or more for women (roughly equivalent to five or four American standard drinks, respectively). In Australia, binge drinking is also known as risky single occasion drinking (RSOD) and can be classified by the drinking of seven or more standard drinks (by males) and 5 or more standard drinks (by females) within a single day. When BEACH (Bettering the Evaluation of care and health) conducted a study which gathered information of people over the age of 18, it defined binge drinkers as those who consumed six or more standard drinks on one occasion whether that be weekly or monthly.

The above definitions are limited in that they do not take into account the time period over which the drinking occurs or the body mass of the person drinking. A person could be defined as a binge drinker even if he or she never becomes intoxicated. The term, however, has succeeded in drawing public awareness to the problem of excess drinking..

Other, less common definitions rely on blood alcohol concentration (BAC). For example, the National Institute on Alcohol Abuse and Alcoholism (NIAAA) defines the term "binge drinking" as a pattern of drinking that brings a person’s blood alcohol concentration (BAC) to 0.08 grams percent or above. Whatever the numerical definition used, heavy drinking or rapid consumption over a short period of time with the intention of becoming intoxicated is often implied when the term is used colloquially, since four or five drinks consumed over the course of a whole day and as an accompaniment to meals will not have the same effects as the same amount consumed over a couple of hours on an empty stomach.

An alternative colloquial term for binge drinking, "going on a bender", formerly implied a drinking spree of several days.

Different concentrations of alcohol in the human body have different effects on the subject.

The following lists the common effects of alcohol on the body, depending on the blood alcohol concentration (BAC). However, tolerance varies considerably between individuals, as does individual response to a given dosage; the effects of alcohol differ widely between people. Hence, BAC percentages are just estimates used for illustrative purposes.

- Euphoria (BAC = 0.03% to 0.12%):

- Overall improvement in mood and possible euphoria

- Increased self-confidence

- Increased sociability

- Decreased anxiety

- Shortened attention span

- Flushed appearance

- Impaired judgment

- Impaired fine muscle coordination

- Lethargy (BAC = 0.09% to 0.25%)

- Sedation

- Impaired memory and comprehension

- Delayed reactions

- Ataxia; balance difficulty; unbalanced walk

- Blurred vision; other senses may be impaired

- Confusion (BAC = 0.18% to 0.30%)

- Profound confusion

- Impaired senses

- Analgesia

- Increased ataxia; impaired speech; staggering

- Dizziness often associated with nausea ("the spins")

- Vomiting (emesis)

- Stupor (BAC = 0.25% to 0.40%)

- Severe ataxia

- Lapses in and out of consciousness

- Unconsciousness

- Anterograde amnesia

- Vomiting (death may occur due to inhalation of vomit (pulmonary aspiration) while unconscious)

- Respiratory depression (potentially life-threatening)

- Decreased heart rate (usually results in coldness and/or numbness of the limbs)

- Urinary incontinence

- Coma (BAC = 0.35% to 0.80%)

- Unconsciousness (coma)

- Depressed reflexes (i.e., pupils do not respond appropriately to changes in light)

- Marked and life-threatening respiratory depression

- Markedly decreased heart rate

- Most deaths from alcohol poisoning are caused by dosage levels in this range.

Public health practitioners have attempted to look at substance use from a broader perspective than the individual, emphasizing the role of society, culture, and availability. Some health professionals choose to avoid the terms alcohol or drug "abuse" in favor of language they consider more objective, such as "substance and alcohol type problems" or "harmful/problematic use" of drugs. The Health Officers Council of British Columbia — in their 2005 policy discussion paper, "A Public Health Approach to Drug Control in Canada]" — has adopted a public health model of psychoactive substance use that challenges the simplistic black-and-white construction of the binary (or complementary) antonyms "use" vs. "abuse". This model explicitly recognizes a spectrum of use, ranging from beneficial use to chronic dependence.

Include the following:

- Depression

- Shaking

- Feeling unreal

- Appetite loss

- Muscle twitching

- Memory loss

- Motor impairment

- Nausea

- Muscle pains

- Dizziness

- Apparent movement of still objects

- Feeling faint

- Noise sensitivity

- Light sensitivity

- Peculiar taste

- Pins and needles

- Touch sensitivity

- Sore eyes

- Hallucinations

- Smell sensitivity

All sedative-hypnotics, e.g. alcohol, barbiturates, benzodiazepines and the nonbenzodiazepine Z-drugs have a similar mechanism of action, working on the GABA receptor complex and are cross tolerant with each other and also have abuse potential. Use of prescription sedative-hypnotics; for example the nonbenzodiazepine Z-drugs often leads to a relapse back into substance misuse with one author stating this occurs in over a quarter of those who have achieved abstinence.

Alcohol intoxication, also known as drunkenness among other names, is a physiological condition that may result in psychological alterations of consciousness. Drunkenness is induced by the ingestion or consumption of alcohol in a living body. Alcohol intoxication is the result of alcohol entering the bloodstream faster than it can be metabolized by the body. Metabolism results in breaking down the ethanol into non-intoxicating byproducts.

Some effects of alcohol intoxication, such as euphoria and lowered social inhibition, are central to alcohol's desirability as a beverage and its history as one of the world's most widespread recreational drugs. Despite this widespread use and alcohol's legality in most countries, many medical sources tend to describe any level of alcohol intoxication as a form of poisoning due to ethanol's damaging effects on the body in large doses. Some religions consider alcohol intoxication to be a sin.

Symptoms of alcohol intoxication include euphoria, flushed skin, and decreased social inhibition at lower doses, with larger doses producing progressively severe impairments of balance, and decision-making ability as well as nausea or vomiting from alcohol's disruptive effect on the semicircular canals of the inner ear and chemical irritation of the gastric mucosa.

Sufficiently extreme levels of blood-borne alcohol may result in coma or death.

The short-term effects of alcohol (also known formally as ethanol) consumption–due to drinking beer, wine, distilled spirits or other alcoholic beverages–range from a decrease in anxiety and motor skills and euphoria at lower doses to intoxication (drunkenness), stupor, unconsciousness, anterograde amnesia (memory "blackouts"), and central nervous system depression at higher doses. Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into nearly every cell in the body.

The concentration of alcohol in blood is measured via blood alcohol content (BAC). The amount and circumstances of consumption play a large part in determining the extent of intoxication; for example, eating a heavy meal before alcohol consumption causes alcohol to absorb more slowly. The amount of alcohol consumed largely determines the extent of hangovers, although hydration also plays a role. After excessive drinking, stupor and unconsciousness can occur. Extreme levels of consumption can lead to alcohol poisoning and death (a concentration in the blood stream of 0.40% will kill half of those affected). Alcohol may also cause death indirectly, by asphyxiation from vomit.

Alcohol can greatly exacerbate sleep problems. During abstinence, residual disruptions in sleep regularity and sleep patterns are the greatest predictors of relapse.

Excessive alcohol intake is associated with an elevated risk of alcoholic liver disease (ALD), heart failure, some cancers, and accidental injury, and is a leading cause of preventable death in industrialized countries. However, extensive research has shown that moderate alcohol intake is associated with health benefits, including less cardiovascular disease, diabetes, and hypertension.

An understanding of the inverse relationship between alcohol consumption and atherosclerosis was understood as early as 1904. The observation of a lower risk of cardiovascular disease (CVD) in France despite a diet rich in saturated fat was labeled the French Paradox. While much concerning this paradox remains unclear, some have suggested that the higher consumption of red wine in France results in lower CVD. Although the reduced incidence of CVD disease associated with moderate alcohol consumption is well established, many physicians have been wary of promoting the use of alcohol for this benefit considering the many negative effects of excessive alcohol consumption.

Binge drinking occurs when students drink large amounts of alcohol in a relatively short space of time in order to feel the full effects of alcohol consumption. The National Institute of Alcohol Abuse and Alcoholism defines binge drinking as a pattern of drinking that brings a person's blood alcohol concentration, also known as BAC, to 0.08 grams percent or above. This is usually seen when men consume five or more drinks, and when women consume four or more drinks in a two-hour time period.

Young adults who participate in binge drinking experience higher rates of physical and sexual assault, and unwanted, unplanned, and unprotected sexual activity. There are also links between heavy alcohol consumption and depression.

The motivations among young students have changed as well. In recent years, more students are drinking with the intended purpose of getting drunk.