There are a lot of misconceptions about drugs. But to develop smart drug policies and figure out how to deal with health issues related to drug use, we need accurate information.
That need for accurate information is what drove British psychiatrist David Nutt to develop scales to assess exactly how dangerous and addictive drugs actually are.
For a 2007 study published in The Lancet, Nutt convened two groups of independent experts to rate the addictiveness and harmfulness of 20 different drugs (the ratings of one group of psychiatrists were used to corroborate the assessment of a larger group).
Addiction was measured using three components: how pleasurable a using a substance was, how much psychological dependence it induced, and how physically dependent it made its users.
Experts rated each variable on a scale of 0 to 3. Based on that scale, these are the 10 most addictive drugs:
As you can see, heroin was by far the most addictive, scoring a three in terms of the pleasure it gave users and hitting the same high score for causing physical and psychological dependence.
As the study points out, it's interesting that legal status doesn't necessarily have anything to do with addictiveness or harm. Tobacco and alcohol both rank fairly high in terms of addictiveness but remain legal, while other illegal substances like cannabis, LSD, and ecstasy fell lower on the list.
You can check out Nutt's full analysis of the harm and addictiveness ratings of drugs in Table 3 of the study; he calculated the mean score of each of the three variables (pleasure, psychological dependence, and physical dependence) rather than adding them up as we did here.
