For decades, researchers have ranked the most addictive drugs in the world. A variety of factors influence the addictiveness of a substance, such as the degree of tolerance a person develops after repeated use and the intensity of the drug’s withdrawal symptoms.
The most addictive drugs can cause widespread addiction and public health problems. A number of researchers have conducted studies to rank the addictiveness of specific drugs using a variety of factors.
In 2007, British psychiatrist David Nutt and a team of addiction experts investigated the most harmful drugs. In a study published in The Lancet, Nutt’s team assessed the harm, dependence and potential misuse associated with 20 drugs.
According to Nutt and his team, the top five most addictive drugs are:
Addictive drugs exert significant changes on the central nervous system. Substances such as alcohol and heroin increase dopamine levels in the brain, producing euphoric effects. Over time, drug use can cause compulsive behavior, dependence and severe withdrawal symptoms.
Research conducted by Nutt and his team revealed that heroin, stimulants, depressants, nicotine products and street methadone had the highest potential for abuse and addiction.
Nutt and colleagues ranked heroin as the most addictive drug. Made from extracts collected from the opium poppy plant, heroin is an opioid that is sold as a white or brownish powder. Heroin users commonly inject the drug into their veins to produce a high. It can also be swallowed or smoked.
After the euphoric effects of heroin subside, people often experience a dreamy state during which they are unaware of their surroundings. Heroin use is associated with drowsiness, nausea, respiratory depression, coma and overdose.
Heroin has exacerbated the U.S. opioid epidemic. According to the National Institute on Drug Abuse, more than 15,400 Americans died from a heroin overdose in 2016. The drug is banned in the United States.
Cocaine was the next most addictive drug in the study. The stimulant is available on the street as a white crystal powder that can be snorted, injected, smoked or rubbed into the gums. Some people inject a mixture of cocaine and heroin, known as speedball.
Individuals experience an intense rush of euphoria and energy after using cocaine. The drug triggers a buildup of dopamine in the brain, which causes the high. But repeated use can increase a person’s tolerance to cocaine, making them require more of the drug to achieve the desired effects.
Some surgeons prescribe cocaine for medical purposes, but recreational cocaine use is illegal in the United States. The drug can lead to addiction, overdose or death. In 2016, more than 10,600 Americans died of cocaine overdose.
Tobacco use includes smoking, chewing or sniffing products that contain nicotine. According to the U.S. Department of Health and Human Services, about 20 percent of adults and teenagers smoke.
Nicotine can be found in a host of tobacco products, including:
Tobacco use harms your physical health. More than 16 million people have contracted at least one disease because of smoking. Since 1964, more than 20 million people in the United States have died because of smoking.
Nutt’s study ranked street methadone as the fourth most addictive substance. In clinical settings, addiction experts provide methadone to wean people off opioids. The drug is designed to reduce cravings and prevent opioid withdrawal symptoms.
When taken as prescribed, methadone is generally safe and effective. Many people receiving methadone treatment can continue to contribute to society. But when the medication is misused, it can lead to lightheadedness, hallucinations and addiction.
Street methadone is methadone sold to someone without a prescription. The drug does not produce a high unless it is taken in significantly high doses, but it can lead to overdose. Many street methadone users take the drug to alleviate opioid withdrawal symptoms.
Barbiturates depress the central nervous system, causing euphoric and sedative effects. These drugs can reduce anxiety and inhibitions, but they can also impair memory and increase irritability and paranoia.
People who use barbiturates can easily develop a tolerance. Misusing this class of drugs can lead to severe health problems, including addiction and overdose. Signs of barbiturate overdose include clammy skin, dilated pupils, shallow breathing and coma.
Along with heroin, cocaine and street methadone, Nutt’s team ranked barbiturates highly in all harm-related categories.
While Nutt’s research team found that heroin, cocaine, nicotine, methadone and barbiturates carried the highest risk for dependence, other substances also showed high dependency rates.
Alcohol was also one of the most harmful and addictive substances in Nutt’s study. Drinking too much can cause brain, heart and liver problems. About 18 million Americans suffer from an alcohol use disorder, according to the U.S. National Library of Medicine. Drinking has also been linked to cancer.
Benzodiazepines are used to treat anxiety and depression. This group of drugs can cause motor incoordination, delirium and hallucinations. Extensive use of benzodiazepines can increase tolerance and result in dependence.
Amphetamines are stimulants that are often prescribed to treat attention-deficit/hyperactivity disorder. However, misuse of Adderall and other amphetamines can cause increased blood pressure, insomnia and a psychosis similar to schizophrenia.
The addictiveness of drugs can be measured using a variety of factors. Nutt and colleagues analyzed each substance based on physical and psychological dependency, physical harm and societal harms. Dependence was based on pleasurable effects, tolerance, withdrawal symptoms and the drug’s ability to influence repeated use.
In the 1990s, Dr. Jack E. Henningfield of the National Institute on Drug Abuse and Dr. Neal L. Benowitz of the University of California at San Francisco each ranked the six most addictive drugs.
Rankings for addictiveness were based on five problem areas, including:
Henningfield ranked nicotine as the most addictive substance, followed by heroin, cocaine, alcohol, caffeine and marijuana. He said that heroin caused the second most intense withdrawal symptoms, followed by nicotine, cocaine, caffeine and marijuana.
According to Henningfield’s rankings, alcohol caused the highest level of intoxication, and it had the most serious withdrawal symptoms. Alcoholism can lead to delirium tremens, a severe form of alcohol withdrawal characterized by sudden and severe changes to the nervous system.
Both addiction experts found that cocaine ranked highest for reinforcement, which is a measure of a substance’s ability to drive repeated use based on human and animal tests.
Benowitz concluded that alcohol had the most serious withdrawal symptoms and caused the highest level of intoxication. His rankings showed that cocaine produced the strongest cravings of the six substances. Like Henningfield, Benowitz found that addiction to nicotine was the most common and that marijuana addiction was the least common.
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