Personally, I've always felt I had a personality that is prone to addiction, so I've stayed away from even alcohol on a regular basis. (Though at one point I was having my favorite alcoholic drink every night... I stopped when I realized what I was doing.)
Even breaking away from caffeine (again) is tough for me. Soda was also tough, and I ended up on soda water instead and still drink way too many of those.
I've also spent too much money on mobile gacha games, but because I know my personality, I managed to keep it from spiraling out of control. (Some people would even say the amount I spent wasn't a big deal, but it was far more than a single game is worth, so it's a sign that I was going wrong.)
Someone else asked how addiction feels, and I almost answered there, but didn't because I'm sure they meant hard addiction that you need help to correct, and I haven't been there. But as far as I've been, it's an almost-uncontrollable desire and subsequent rationalization and then capitulation. Each time. Fighting the feeling is depressing, even if everything else is going great. I only ever escape when I make myself feel worse about doing the thing than I feel from not doing it.
Legal substances also have lots of information readily available around them - if I go to my pharmacy and ask for ibuprofen, they will tell me the dosages in advance. If I go to my doctor and they put me on oxycodone, they will give me a dose that they think is safe, (and in theory, a plan to reduce my dependence on them) without judgement. If you develop an opiod addiction, your support options are much more limited.
Also, Joplin took heroin AND massive quantities of alcohol on the day of her death. It will be close to saying that when someone dies in a car crash while DUI, driving is the real and unique problem here.
But the drug-war irrationality is better exposed by taking a look at weed and MDMA. Two quite safe substances (certainly more safe than alcohol), with clear medical applications, and forbidden just because some ignorant decided to put them in Schedule I. MDMA at the time of its prohibition was being used in psychotherapy with success in tens of thousands of patients [1]. Today, no medical use is recognized, and being in Schedule I (making it un-researchable), none will be. I wouldn't be too surprised that some country discover that it could be used as a treatment for depression or PTSD.
So heroin is actually pretty safe if used correctly.
Not many legal drugs has such short list of side effects.
People die when they over-dose (which more often than not happens because they don't know exactly what they're getting, or the purity of it) or mix with other substances that they shouldn't.
A person quits for a while, decides to start using again and shoots up their usual dose for which they no longer have sufficient tolerance.
If that person knew that this is a common way people end up killing themselves, they probably wouldn't make this mistake.
"Repeated heroin use changes the physical structure and physiology of the brain, creating long-term imbalances in neuronal and hormonal systems that are not easily reversed. Studies have shown some deterioration of the brain’s white matter due to heroin use, which may affect decision-making abilities, the ability to regulate behavior, and responses to stressful situations."
I expected something more damning. Unfortunately, I feel that we don't have enough studies (incl. long-term ones) when it comes to recreational drugs.
Users often mix heroin with benzos and/or alcohol which increases the level of risk enormously. The vast majority of overdoses are caused by mixing CNS depressants in with heroin, not by heroin use alone.
If you can't get a steady supply then withdrawals are vicious and can cause a host of other problems (crime in order to get money for more heroin being a commonly cited one).
One of the ways that heroin itself can cause overdose deaths is relapses - users may take a dose that they were previously tolerant to. I believe this is still far less of a danger than combining with other substances.
Many classic drugs (as opposed to research chemicals which introduce small molecular changes to circumvent banns on another substance) are pretty safe or at least have a well known safety profile.
Here's a reddit famous account from someone claiming to be an opiate addict that some find enlightening/haunting: https://www.reddit.com/r/IAmA/comments/wnj2d/iama_heroin_add...
> Hart presents himself as a model drug user. “I am now entering my fifth year as a regular heroin user,” he writes. “I do not have a drug-use problem. Never have. Each day, I meet my parental, personal, and professional responsibilities. I pay my taxes, serve as a volunteer in my community on a regular basis, and contribute to the global community as an informed and engaged citizen. I am better for my drug use.”
Anyone who has plumbed the depths of addiction either with a family member or personally has spoken this exact paragraph, potentially word for word. It's a rationalization for addiction, and honestly the most common and basic one.
Good luck to him as he descends through addiction. He's extremely educated and very assured of his self-perception so for him to hit Step 1: Realize you have a Problem, is going to be a lot harder than the average person.