Alcohol use disorder can be mild, moderate or severe, based on the number of symptoms you experience. Signs and symptoms may include:

• Being unable to limit the amount of alcohol you drink
• Wanting to cut down on how much you drink or making unsuccessful attempts to do so
• Spending a lot of time drinking, getting alcohol or recovering from alcohol use
• Feeling a strong craving or urge to drink alcohol
• Failing to fulfill major obligations at work, school or home due to repeated alcohol use
• Continuing to drink alcohol even though you know it's causing physical, social or interpersonal problems
• Giving up or reducing social and work activities and hobbies
• Using alcohol in situations where it's not safe, such as when driving or swimming
• Developing a tolerance to alcohol so you need more to feel its effect or you have a reduced effect from the same amount
• Experiencing withdrawal symptoms — such as nausea, sweating and shaking — when you don't drink, or drinking to avoid these symptoms

Alcohol use disorder can include periods of alcohol intoxication and symptoms of withdrawal.

Alcohol intoxication results as the amount of alcohol in your bloodstream increases. The higher the blood alcohol concentration is, the more impaired you become. Alcohol intoxication causes behavior problems and mental changes. These may include inappropriate behavior, unstable moods, impaired judgment, slurred speech, impaired attention or memory, and poor coordination. You can also have periods called "blackouts," where you don't remember events. Very high blood alcohol levels can lead to coma or even death.

Alcohol withdrawal can occur when alcohol use has been heavy and prolonged and is then stopped or greatly reduced. It can occur within several hours to four or five days later. Signs and symptoms include sweating, rapid heartbeat, hand tremors, problems sleeping, nausea and vomiting, hallucinations, restlessness and agitation, anxiety, and occasionally seizures. Symptoms can be severe enough to impair your ability to function at work or in social situations.

What is considered 1 drink?

The National Institute on Alcohol Abuse and Alcoholism defines one standard drink as any one of these:

• 12 ounces (355 milliliters) of regular beer (about 5 percent alcohol)
• 8 to 9 ounces (237 to 266 milliliters) of malt liquor (about 7 percent alcohol)
• 5 ounces (148 milliliters) of unfortified wine (about 12 percent alcohol)
• 1.5 ounces (44 milliliters) of 80-proof hard liquor (about 40 percent alcohol)

Genetic, psychological, social and environmental factors can impact how drinking alcohol affects your body and behaviour. Theories suggest that for certain people drinking has a different and stronger impact that can lead to alcohol use disorder.

Over time, drinking too much alcohol may change the normal function of the areas of your brain associated with the experience of pleasure, judgment and the ability to exercise control over your behaviour. This may result in craving alcohol to try to restore good feelings or reduce negative ones.

Alcohol use may begin in the teens, but alcohol use disorder occurs more frequently in the 20s and 30s, though it can start at any age.

• Steady drinking over time. Drinking too much on a regular basis for an extended period or binge drinking on a regular basis can lead to alcohol-related problems or alcohol use disorder.
• Starting at an early age. People who begin drinking — especially binge drinking — at an early age are at a higher risk of alcohol use disorder.
• Family history. The risk of alcohol use disorder is higher for people who have a parent or other close relative who has problems with alcohol. This may be influenced by genetic factors.
• Depression and other mental health problems. It's common for people with a mental health disorder such as anxiety, depression, schizophrenia or bipolar disorder to have problems with alcohol or other substances.
• History of trauma. People with a history of emotional or other trauma are at increased risk of alcohol use disorder.
• Having bariatric surgery. Some research studies indicate that having bariatric surgery may increase the risk of developing alcohol use disorder or of relapsing after recovering from alcohol use disorder.
• Social and cultural factors. Having friends or a close partner who drinks regularly could increase your risk of alcohol use disorder. The glamorous way that drinking is sometimes portrayed in the media also may send the message that it's OK to drink too much. For young people, the influence of parents, peers and other role models can impact risk.

Alcohol depresses your central nervous system. In some people, the initial reaction may be stimulation. But as you continue to drink, you become sedated.

Too much alcohol affects your speech, muscle coordination and vital centers of your brain. A heavy drinking binge may even cause a life-threatening coma or death. This is of particular concern when you're taking certain medications that also depress the brain's function.