There are some cases where harm to self is effectively harm to another because the harm produces a person who is so radically different from the person bestowing the harm that he or she loses relevant continuity of identity with that prior person. This can be exacerbated by producing, also, a person with diminished capacity to consent to the harm.
Part 1: Wrongful Life
Imagine that people intentionally damage their reproductive systems so that they will only produce offspring with a genetic condition that causes severe pain throughout life. Then, assume further that these people intentionally reproduce. Have they done a wrong in bringing about a person who (1) has no say in his or her coming-to-be and (2) will have a life that is unbearably painful? We can also imagine this with some sort of severe disability, one that makes life potentially unlivable, or some other disorder.
I think many would hold that this is something we should not do: it’s one thing to have and raise a child who has a severe health problem, it’s another to intentionally produce such a child. If you think it’s justified to do so, maybe you can push the thought experiment until it becomes unjustified: perhaps moving to a warzone where child rape and torture are common occurrences, and then intentionally having a child while knowing that you will die within a few months of the child’s birth, and that the child will be left with abusive relatives. Or some such: make up your own Dickens’ story.
If we agree that some such version is wrong, we can agree there is something like a “wrongful life” case.
Part 2: Self Determination
Some people will hold in the existence of wrongful life cases, and also hold that a people have a great deal of leeway about what they do to themselves. So we might hold that it’s morally permissible to get facial tattoos that will make future employment extremely difficult, or to engage in dangerous “extreme” sports that have a very high risk of causing permanent disability, or do other things that put our future welfare at risk.
Liberals and libertarians generally give people a great deal of leeway to self-harm, but very little to harm others. This is, in some sense, the most basic principle of liberalism, at least as understood by the tradition coming out of Mill. In general, this means they would prefer that there not be government regulations against self-harm, or that such regulations would require special justification (for example, that they apply only to people with diminished agency) or only be a by-product of regulations designed to prevent harm to others (for example, a pro-euthanasia libertarian might agree that people should not commit suicide in public to avoid traumatizing others.)
Part 3: Wrongful Self-Creation
Suppose I, an unusually cruel person, wish to cause someone intense and long lasting pain. But I respect the law, so I can only do this to myself. But I do not wish to experience this pain. So: I arrange the following: I will be injured in the spine in a manner that will cause me excruciating pain for the rest of my life, and also experience severe disability. But I also arrange to have my memory wiped.
The latter is not impossible: Su Meck and the victims of Donald Ewen Cameron suffered near-total memory wipes due to head injury in the former case and the use of drugs and sensory deprivation tanks in the latter.
So what will happen is that I will produce a person, with no knowledge of how he was produced, no memory of any decision to become who he is, nor any real psychological connection to me, assuming the cases above are representative, and for the purpose of the thought experiment, we can just stipulate that this will be the effect. In Su Meck’s case, for example, people who knew her before say that the person who emerged after the memory wipe had a very different personality from the one before. Further, this being will be in constant pain.
It seems like, if I think, as liberals and libertarians do, that I should be allowed to self-harm, if I also think that there are wrongful life cases, as in part 1 above, I may have conflicts about how to assess this case.
On the one hand, there is a description of that is done here that makes it seem like it is merely self-harm, and not harm to others. We can even add that I have made enough money that I can put it towards the care of this future self, so that society is not burdened by his existence. In fact, there’s some societal benefit in that people are employed to care for him.
On the other hand, it seems that this might no longer be myself, in any meaningful way. I’ll have lost all memory and connection of character to the prior person. So is this a case of wrongful life?
Note that the full memory wipe means that the person will have to be taught to talk and read and write and etc. So this is highly analogous to creating a child, and, in this case, intentionally creating a child with very low quality of life.
Part 4: Conclusion: Edicts Against Self-Harm as Edicts Against Other-Harm
Granted that there are some cases in which harm to a future self is effectively harm to another, it might be the case that many such cases exist. Given enough time, many if not most people will undergo radical changes in personality, and in any event most of our memories are not retained for very long, and those that are retained are increasingly unreliable as time progresses. A foolish decision I make when I’m 15 might seriously impair my future life, and I could well be said to be harming some future person who is, at best, only mildly continuous with me.
While I may have bodily continuity with this future person (though we could imagine cases where I don’t, say due to extensive prosthesis including slow replacement of brain parts with computer parts) I may, as in Derek Parfit’s Russian nobleman case, have little in common morally or psychologically with this future person.
Can I be forbidden, either morally or legally, from making decisions that harm my future self, even if I agree that I have a great deal of moral and legal leeway to harm myself? That is, taking a liberal/libertarian ethic, can I still argue that there are things I cannot do to myself, even though they harm only me (or some future me) and not anyone else? I think, given the above, some sort of argument can be made in at least some cases. Those would be cases where I create a future self who would not have consented to the harm he receives, or who would be unable to consent.
Thus, there may be a legal case, even in strictly libertarian/liberal terms, for laws against self harm, at least when the self-harm is related to a future person with limited continuity with the person committing the harm.
 See http://www.washingtonpost.com/local/education/gaithersburg-woman-earns-college-degree-two-decades-after-complete-memory-loss/2011/05/19/AFWAMg8G_story.html and her autobiography, “I Forgot To Remember,” Simon & Schuster, 2014
 There’s a brief rundown of Cameron’s work here: http://en.wikipedia.org/wiki/Donald_Ewen_Cameron#Project_MKUltra . Fuller discussion can be found in Anne Collins’ “In the Sleep Room: The Story of CIA Brainwashing Experiments in Canada.” Toronto: Key Porter Books. 1988/1998