It is a complex subject, in which even people supposed to know professionally tend to, often wilfully, ignore part of the available knowledge, because is not linked to their background (e.g. sociology vs neurobiology), for ideological reasons, for personal interest (give me my research money, ego, afraid of having to realise they were wrong and that may have impacted others, etc.), etc.
That is also not helped by the fact there is still lots being learnt about e.g. our brain, the fact as humans we are not really a linear machine but a complex system, the fact that at the start addictions was seen and studied as a social phenomenon and for many years people when saying "addiction" pictured it as a problem of "weakness of spirit" and with no physiological aspect (abundantly proven wrong scientifically, but still hold as opinion by many), and that there are interest at stake that may be in favour of not talking too much about some aspects of it and even shun the results of the research.
Hint, metamphetamines are regularly given, used and suggested for use to military staff (pilots, example) of a certain country I will not mention here to avoid the risk of getting in politics (which is forbidden on F95), and certain States in a certain country ;-) are making lots of money from some recreational selling
, even if it was present in some fora as a decision not based on economic interest.
Just an example of complications, referring to one of the substances you mention, is that aside any other factors, the potency of one of the substances you mentioned is directly linked empirically (but also if one thinks well, it also makes sense from the point of view of the brain) with the speed of getting symptoms of addiction like craving. Potency which tendentially goes with "purity", and that open another can of worms, because if it is "cut" with the "wrong" thing, one dose can kill you directly.
At the same time, it is true that some substance that can give addiction, can even be useful and helpful in certain medical situations, or even have positive impact (e.g. munching coca leaves in the Andes is not the same as in London, marijuana can help in pain palliative therapy for cancer, in moderate quantities wine has been associated with positive health effects), though even there, there can be then individual factors (e.g. "resistance" to alcohol is associated with metabolism and genetic factors, and I would not suggest to give any alcohol to people who are allergic to it like a couple of people I met in the past
).
But to close this long post
, I have a suggestion for Zorlun, if he wants to make a possible ending with addiction, but without, or anyway with less problems than others, and almost, or no, impact on the look...
Gambling. It can give addiction, and there is not even need for Myriam, who is rich, to go bankrupt, she may just decide she wants to hide the problem and pay her debts "in nature" ;-), and/or through some "films" and other episodes similar to some that already happened (there could be a number of ideas without even introducing new characters, imagine if one of those collecting the payment was the mobster).
She does not even need to become 100% addict forever, is sufficient she gets a few big losses she has to deal with, and that may actually give her a shock to get out of it, so can even allow for a kind of "happy ending" (sort of).
Gambling addiction can influence a bit the behaviour, and when people start dedicating too many resources to it and obsess about it, at least indirectly the aspect, but a lot of people develop a form of addiction to gambling well before they reach such a level of obsession that it is physically visible.
Or if he wants to add a maybe more evil twist, can be one of the other characters that gets the debts, and then tries to "use" her to clear the debt, there is at least one character I could see very well doing that (hint to know who I am thinking about, he is not blood related).