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What Is The Most Addictive Drug In The World?

Recently I wrote an article documenting the most addictive drugs based on a study conducted in 2007 by David Nutt. The study also included some newer findings from an undocumented Dutch study that some news websites had published. In both the study by David Nutt and the Dutch study, the most addictive drug in the world was said to be heroin. Other reports based on surveys of psychiatrists and even older speculations from researchers assumed heroin was the most addictive drug.

Although smoking crack cocaine is considered just as pleasurable as doing cocaine, it has a slightly lower rating of psychological dependence and a significantly lower rating of physical dependence than heroin. In fact, street methadone is considered more physically addicting than cocaine – in large part due to its opioid effects. Crack cocaine is considered the second most-addictive drug to heroin, but it doesn’t pose the same levels of psychological and physical dependence.

Most addictive drug in the world: Heroin (diacetylmorphine)

Heroin is considered more addictive than other drugs based on addiction scales due to the fact that it’s extremely pleasurable, and likely to create both physical and psychological dependence. Heroin has been around since the 1870s and was created by combining the molecule morphine with acetyl groups. When a person uses heroin, it enters the body and converts into the drug morphine, giving users a significant physical and psychological high.

The difference between standard morphine and heroin is that it has a significantly higher bioavailability, crossing the blood-brain barrier quicker than morphine and thus eliciting a greater degree of intoxication. The drug itself depresses the central nervous system, slowing down heart rate, breathing, and allowing the user to experience the most potent physical and psychological “high” of any drug. It has an effect by binding to the mu-opioid receptors, resulting in a significant analgesic response and the release of endorphins, which trigger an unparalleled euphoria.

The drug takes away all feelings of anxiety, depression, and makes users feel happy. A major problem with the drug is that repeated usage results in rapid development of tolerance.  Those who frequently use heroin will constantly chase their initial high, eventually depleting their body’s natural ability to produce endorphins and becoming reliant on the drug for functioning. Upon depletion of endorphins, a person will experience a significant degree of depression, anxiety, and reward-deficiency syndrome.

Using this drug alters opioid receptor functioning in the brain, and will lead to highly unpleasant withdrawal symptoms when discontinued. (Read: Heroin withdrawal symptoms). The combination of the pleasure derived from the drug, the rapid development of tolerance, and severe withdrawals makes heroin the most addictive drug in the world.

Why heroin is considered the most addictive drug? The Research.

Universally heroin is considered the most addictive drug based on a number of different addiction studies and evaluations – regardless of the definition or measurement of “addiction.” Perhaps the most reliable study conducted on determining addictiveness of various drugs is the 2007 study by David Nutt. However, even in other studies and rating scales (e.g. Henningfield / Benowitz), heroin is the clear-cut most addictive substance. There doesn’t even seem to be controversy or debate as to what the most addictive drug is – it’s heroin by a longshot.

David Nutt (2007)

David Nutt and colleagues conducted a study in 2007 in attempt to measure harm caused by 20 popular drugs. This study didn’t take into account “every drug,” but most common illicit and controlled substances were mentioned. In this study, the most addictive substance was heroin, and it wasn’t really a close second.

  • Pleasure: 3.0
  • Psychological dependence: 3.0
  • Physical dependence 3.0

Dutch Study

An alleged Dutch study followed up Nutt’s initial study with a rating scale from 0 to 3 for addiction; 3 is considered most addictive while 0 is considered not addictive. The rating for heroin in this particular study was 2.89 – only slightly higher than crack cocaine, but still higher nonetheless.  This provides additional confirmation for heroin being considered the most addictive drug in other research.

  • Addiction rating: 2.89

Henningfield Ratings

Dr. Jack E. Henningfield of the National Institute on Drug Abuse put together a ranking system for substances that are thought to be addictive. This was less comprehensive than the other studies such as that by David Nutt, but it is considered to be somewhat accurate. He ranked substance addiction potential based on factors including: withdrawal, reinforcement, tolerance, dependence, and intoxication. Heroin had the highest addiction rating (lower number equals greater potential). The next most addictive substance was considered alcohol (12) and nicotine (15) and cocaine (15).

  • Addiction potential: 9 (Heroin)

Benowitz Ratings

In similar manner to Henningfield, Dr. Neal L. Benowitz of the University of California at San Francisco also ranked six common substances based on the same criteria. His findings yielded slightly different results, but he still had heroin at the top with a composite ranking of 10. In second place he listed cocaine (11) and third place alcohol (13). Although he differs from Henningfield in some ratings, they both agree on the most addictive drug.

  • Addiction potential: 10 (Heroin)

Individual experiences with addiction are not objective

Keep in mind that just because heroin is universally considered the most addictive drug, doesn’t mean everyone will struggle with it to the same degree. Some people may end up having an easier time coming off of heroin than crack cocaine or crystal meth – there is some degree of individual variation. On a subjective basis, one person may have an easier time quitting heroin than nicotine.

Based on objective measures of addiction though, heroin is clearly the most addictive drug in the world. Although crack cocaine may be equal in pleasure to heroin, the psychological and physical dependence ratings are greater (to a significant extent). Many drugs are considered highly addictive and should be avoided, but if there’s one drug that should be avoided more than any other, it’s heroin.

Everyone has their own “opinion” as to what the most addictive drug is based on personal experiences. However, what’s true for one person doesn’t mean it’s the same for everyone. For one person, quitting alcohol may be more difficult than heroin. Understand that individual opinions will differ and be largely subjective. Objectively, the most addictive drug should be considered heroin.

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