That depends on theee things.

The dosage and the person's tolerance. And genetics.

Drugs that are ranked higher for drug addiction typically have strong fast effects and fast loss of the high.

But all drugs have addiction capabilities because of how tolerance in the body works. Tolerance, withdrawal, addiction. All part of the same process.

So back to addiction.

Cocaine. Immediate and intense high. But doesnt last that long. Same for the heroine.

Drugs like meth and adderall are basically exactly like cocaine in many ways except the high is actually more mild (per dose) and lasts longer.

Opiate medications can be seen as similar to heroine but. Last longer and not as strong.

Of course you can take larger doses of either of those two and get a stronger effect.

Even if you don't tho, people still get addicted to both of these more milder forms of cocaine and heroine. But just not at the same risk level.

And the risk declined drastically if taken at therapeutic levels (like following prescription drug directions).

Another thing you have to consider is genetics in brain receptors.

Some people's brain responds strongly in eurphoria to a drug while someone else's does not.

For example. Opiates. I personally do not get euphoria from opiates. I instead get a bad headache and extreme nausea. I had an injection of morphine about a year ago for a ER visit. Not only did it not help the pain at all, I had unpleasant effects from the drug. I was not high. But I was woozy. It was incredibly awful.

I actually told them not to give me optiates because I already knew I didn't tolerate them but that's what I get for going to a 1 star ER.

So how is it possible that a drug like an opiate wouldn't make me high or at the very least block the pain I was having ?

Genetics. My mother is the same. The part of other peoples brain that the opiate drugs bind to, will not accept the drug in my brain. Instead the drug is binding to some other receptors. Starting a cascade of signals that give me delirium, nausea, and a headache.

They are different enough to make a drug have a completely different effect in two animals of the same species.

It's things like that, that make designing drug therapies incredibly difficult.

So even when we try to give a basis run down of what drugs are highest risk, we can't say that's true for everyone.

There is zero chance I could become addicted to opiate based drugs. They literally are aversive to me.

It also means if I get injured and I'm in severe pain, there isn't much that can be done (so pretty big trade off. Here's hoping I don't get a painful terminal cancer).

So at present. Schedule 1 drugs have a specific definition. And that definition indicates a high risk of dependency.

You can read up more about how a drug qualifies for schedule 1. And schedule 2. I think that will help you understand the system better.