Drug addiction, also called substance use disorder, is a dependence on a legal or illegal drug or medication.

Though alcohol and nicotine are legal substances, they are also considered drugs.

When you’re addicted, you’re not able to control your drug use and you may continue using the drug despite the harm it causes. Drug addiction can cause an intense craving for the drug. You may want to quit, but most people find they can’t do it on their own.

Substance use disorders occur when the recurrent use of alcohol and/or drugs causes you clinically and functionally significant impairment, such as health problems, disability, and failure to meet major responsibilities at work, school, or home. They can cause serious, long-term consequences, including problems with your health, relationships, employment, and the law.

You may need help from your doctor, family, friends, support groups or an organized treatment program to overcome your drug addiction and stay drug-free.

The following is a list with descriptions of the most common substance use disorders in the United States.

ALCOHOL USE DISORDER  (AUD)

Excessive alcohol use can increase a person’s risk of developing serious health problems in addition to those issues associated with intoxication behaviors and alcohol withdrawal symptoms. According to the Centers for Disease Control and Prevention (CDC), excessive alcohol use causes 88,000 deaths a year. An estimated 17 million Americans have an AUD.

The definitions for the different levels of drinking include the following:

• Moderate Drinking—up to 1 drink per day for women and up to 2 drinks per day for men
• Binge Drinking—drinking 5 or more alcoholic drinks on the same occasion on at least 1 day in the past 30 days
• Heavy Drinking—drinking 5 or more drinks on the same occasion on each of 5 or more days in the past 30 days

Excessive drinking can put you at risk of developing an alcohol use disorder in addition to other health and safety problems. Genetics have also been shown to be a risk factor for the development of an AUD.

To be diagnosed with an AUD, individuals must meet certain diagnostic criteria, including problems controlling intake of alcohol, continued use of alcohol despite problems resulting from drinking, development of a tolerance, drinking that leads to risky situations, or the development of withdrawal symptoms. The severity of an AUD—mild, moderate, or severe—is based on the number of criteria met.

CANNABIS USE DISORDER

Marijuana is the most-used drug after alcohol and tobacco in the United States. According to SAMHSA data, in 2014, about 22.2 million people ages 12 and up reported using marijuana during the past month. In the past year, 4.2 million people ages 12 and up met criteria for a substance use disorder based on marijuana use.

Marijuana’s immediate effects include distorted perception, difficulty with thinking and problem solving, and loss of motor coordination. Long-term use of the drug can contribute to respiratory infection, impaired memory, and exposure to cancer-causing compounds. Heavy marijuana use in youth has also been linked to increased risk for developing mental illness and poorer cognitive functioning.

Some symptoms of cannabis use disorder include disruptions in functioning due to cannabis use, the development of tolerance, cravings for cannabis, and the development of withdrawal symptoms, such as the inability to sleep, restlessness, nervousness, anger, or depression within a week of ceasing heavy use.

STIMULANT USE DISORDER

Stimulants increase alertness, attention, and energy, as well as elevate blood pressure, heart rate, and respiration. They include a wide range of drugs that have historically been used to treat conditions, such as obesity, attention deficit hyperactivity disorder and, occasionally, depression. Like other prescription medications, stimulants can be diverted for illegal use. The most commonly abused stimulants are amphetamines, methamphetamine, and cocaine.

Symptoms of stimulant use disorders include craving for stimulants, failure to control use when attempted, continued use despite interference with major obligations or social functioning, use of larger amounts over time, development of tolerance, spending a great deal of time to obtain and use stimulants, and withdrawal symptoms that occur after stopping or reducing use, including fatigue, vivid and unpleasant dreams, sleep problems, increased appetite, or irregular problems in controlling movement.

OPIOID USE DISORDER

Opioids reduce the perception of pain but can also produce drowsiness, mental confusion, euphoria, nausea, constipation, and, depending upon the amount of drug taken, can depress respiration. Illegal opioid drugs, such as heroin, and legally available pain relievers such as oxycodone and hydrocodone can cause serious health effects in those who misuse them.

Since 1999, opiate overdose deaths have increased 265% among men and 400% among women. In 2014, an estimated 1.9 million people had an opioid use disorder related to prescription pain relievers and an estimated 586,000 had an opioid use disorder related to heroin use.

Symptoms of opioid use disorders include strong desire for opioids, inability to control or reduce use, continued use despite interference with major obligations or social functioning, development of tolerance, spending a great deal of time to obtain and use opioids, and withdrawal symptoms that occur after stopping or reducing use, such as negative mood, nausea or vomiting, muscle aches, diarrhea, fever, and insomnia.