Some damage may be reversible, but I'd be willing to bet that a lot of damage to the prefrontal cortex is irreversible, from what I've seen...
In general you`d be correct, but if you`re young enough, healthy enough, can find the right supplements, and halt any further neurotoxic activity, you have an EXCELLENT chance of repairing the PFC greatly. It will take a long time, and you will need to stimulate it with mental exercises and a lot of thinking that uses the PFC (video games can help a lot, math, writing, physical exercise {especially cardio} is important, complex reading/analysis, practicing willpower control, etc.). It may never be the same as before, but neuroplasticity is a powerful thing, and the younger you are the better it works. The older you get past 21-23, the lower the chances it'll work amazingly, and the slower it'll be capable of working, in general. After 25, the brain is mature and no longer in the process of molding and structuring itself, so it starts to get a lot harder. Still, even those above forty can achieve amazing results.
It's similar to how people with environmental/accidental brain damage are able to recover from their injury and rediscover neural functions that were impaired. Admitted, the PFC is a tough place to recover if the damage is extensive. But there is hope.
It's not that you CAN'T repair it. It's just that most are too addicted to really try (and do it right), and besides that, most have no ability to stop using neurotoxic chems, one of the prerequisites for serious recovery. Also, even if someone quits and tries to get better, unless they actually have a mental exercise regime it will NEVER work well. The brain is very much like a muscle, and you can't get better if you don't exercise it. Relatively few people have the natural drive to exercise it, especially the PFC region's functions, and those that don't are likely unfortunately either too ignorant to know how to exercise it, or too lacking in tenacity to force themselves to do it.
The brain is a wonderful thing; I study neuroscience, it's my passion. Yes, some damage is quite irreparable, like a huge chunk of neurons dying at once. If there's absolutely no neurons for a particular function/region left to exercise, well, that's like trying to lift weights with a non-existent arm; there's nothing to increase the strength/function OF! Sometimes other regions can take over, but not always. However, if you still have something to exercise, there's SO MUCH you can do, bro!
Nothing will take over for the PFC. Protect it. Don't damage it in the first place. If you do, and, hell, even if you don't, NEVER STOP LEARNING, always keep thinking, and you're on the right path. Once you stop learning new things, and exercising your cognitive faculties, your brain will ATROPHY in important regions, even without the help of neurotoxicity. But if you are driven to always learn (or make yourself do it), and you choose to follow naturally or with intent a proper regime of mental exercise, you've got more than hope, you've got REAL POTENTIAL - The Will, The Parts, the Smarts, and a Repair Guide. The will to achieve PFC recovery and strength, enough brain function left to work from and exercise, the desire or drive to learn constantly, and the knowledge of which actions to promote and which actions to avoid like the plague.
All mammals are possessed of neuroplasticity. Few of them are possessed of prefontal cortices, NONE of them with one like yours. You are the only animal that is flexible enough to consciously CHOOSE which direction to mold your brain growth. The only one with the option to CHOOSE to ameliorate your neural structure and ability, merely by acting and thinking rightly. The others are forced to either alter for the good or bad, by their environment, genetics, and existing brain structure. You need to exercise this choice, it's not always easy, but you can choose to let it wither all away, or make the decision to heal thyself. You are human, you are the universe subjectively experiencing itself, you have an ability to choose your path. Choose brain empowerment. Train your mind; promote neural growth. If you are dedicated to this goal, then you will be thanking yourself for decades while associates who are averse to this kind of "work" are becoming more and more clearly cognitively deficient.
Sorry for all that text, I'm a little bit stimulated, lol. But seriously, your mind, your rules; reject the notion that you are limited, and you will have the keys to a better brain.
Even those who manage to quit for a long time, I've noticed that they never really "came back" all the way, kind of like how when some people do too much acid they never really come back. Not saying it's the same thing, just the closest example I could find...
I'm not sure about that. Why don't they come back? Brain damage from an overdose of acid? Adulterants? Psychosis? Or the development of other mental disorders? I just don't think they "never come back" merely from doing too much acid. That's probably due to other pre-existing issues that have been catalyzed by the lysergic acid diethylamide. And, that said, I think they CAN come back, with the proper treatment and a good regimen for brain health.
Any examples of people who had no serious mental health issues, then took LSD, and were permanently damaged? I'm not doubting that they could exist, I've just never seen it myself. Also qualify, please, what never coming back looks like. What, exactly, is this damage? It must be physical, and it must be either structural change, functional change, or chemical change. I don't know what LSD would do to cause this, and what the damage would like on the brain.
I don't doubt it can damage a person, but I really think that "never coming back" must be serious brain damage caused by overdose, not just doing it too frequently or taking high recreational doses. You don't talk about people never coming back when they do too much of a seizure-inducing drug, for instance, tramadol, and cause serious brain damage. That's just called brain damage from an overdose.
Sorry, I'm not trying to offend you or anyone, I just don't like the phrase "never came back" in relation to LSD, and I've never understood what the damage is, or how it could occur. That's why I assume actual toxic effects due to overdose, not just weird lasting mental alterations that are not rooted in brain damage.
I might have also misread you, I've been up way too long, so sorry if that's the case - please know that I really do respect you and enjoy your contributions.