So by that math, if I try Alcohol twice am I hooked? Or is the relationship logarithmic?

I don't think trying heroin is a good idea, but assigning star values like this is not helpful. If anything, it highlights heroin as a goal drug.

I'm not sure I understand the scale here; there is often not a number of usage to addition, it's often a matter of sustained and/or heavy usage. Yes, some drugs lower that threshold (and I thought cigarettes were much more addictive than alcohol), but it's not a x-time-and-done issue.

Also, note the lack of caffeine on the chart, it being very common drug that is highly addictive

How much more opiate is in a hit of street heroin than your usual medical injection of IV morphine for traumatic pain? I've had the latter and while it was fairly awesome, it's not exactly world-changingly addictive either. I'd rate it about the equal of alcohol on your scale.

I don't have any insight into the values themselves, but each of those are going to have such variances as to make any simple summary useless. Products just to get people to stop smoking are a huge market and many people fail in their attempts to quit. But many people never get hooked in the first place, and even long-term smokers stopping cold is not that uncommon. For alcohol, I've never known a non-problem drinker who couldn't give it up at any time (for weight loss, Lent, personal challenge, avoiding prescription drug interaction). Similarly, my understanding is that heroin is incredibly addictive for some people but not others.

> if you try heroin once, you're addicted. Is that close to be correct?

Absolutely not. Most likely you'll feel sick and vomit, then be really high for a few hours and then afterwards feel incredibly guilty and decide to never make a habit of it. The number one factor in addictiveness is whether or not you have a "crappy life", probably closely followed by whether or not you have an addictive personality and whether or not you'd prefer one cookie now or two cookies in ten minutes.

Trying all drugs is illuminating because you learn that there is no "magic" drug that feels so amazing that all your problems melt away. That's a fairy tale.

Different people seem to have different propensity for addiction, and it is likely genetic. There's also such thing as psychological dependence, which is different from physical addiction but can be just as powerful. I don't think you can create a simple score card for addictive potential that applies equally to everyone.