A would-be murderer or rapist who is prevented from murdering or raping by thoughts of the harm that his action would do to his victim may go on living as he wishes, for the most part - he simply may not murder or rape. But a would-be suicide who is prevented from committing suicide by thoughts of the harm his suicide would do to those around him is forced into a different sort of arrangement. He may not go on living as he wishes - he does not wish to live at all. He is living entirely for the benefit of others.
A p-zombie, or philosophical zombie (though David Chalmers at times calls it a phenomenal zombie), is a person who looks and acts just like a regular person, but who has no subjective experience. In explaining a problem in consciousness studies, the exact nature of which is irrelevant to this piece, Raymond Smullyan famously proposed a form of p-zombie suicide:
A man wants to commit suicide but does not want to cause his family any grief. He finds out about an elixir he can take which will kill him, i.e., separate his soul from his body, but leave his body intact to wake up, go to work, play with the kids, keep the wife satisfied and bring home the bacon. [From "zombies and p-zombies" in the Skeptic's Dictionary.]
Indeed, we would-be suicides who wish to cause as little harm as possible to those around us wait anxiously for news from the promising field of p-zombie therapy.
Unfortunately, in addition to being (arguably) a logical impossibility, a p-zombie is a singularly unsatisfying sort of companion. For those who believe that subjective pleasure is all that matters, p-zombiehood is fine; but for those to whom truth matters - for those to whom there is value beyond subjective experience - to love a p-zombie would be as awful as having a faithless lover whose faithlessness went undiscovered. Denying genuine intersubjectivity to those around us must be practically as cruel as simply killing ourselves.
There is a sense, though, in which all genuine would-be suicides are, sort of, zombies. We are living wholly for others - while we retain experience and genuinely interact with others, we are no longer, in a deep way, agents of our lives. We get up in the morning, work, eat, speak, have sex, do the dishes, not out of desire or will, but, ultimately, out of concern for others. Just as others would be harmed by our turning ourselves into p-zombies without subjectivity, they are harmed by having us around minus the will to live.
In David Rieff's memoir of the death of his mother, Susan Sontag, he repeatedly expresses his guilt over not doing enough, over going along with her unrealistic fantasy of survival or not going along with it wholeheartedly enough. And yet he recognizes that to live in such a way as to avoid guilt after the death of another - to live always with another in mind above all - is to void oneself. He says,
To live without guilt after the death of a loved one, a person would have to accede to literally everything the other person wanted. And what this really means is living one's entire life in attendance of the other's death since there is no way of being an emotional Jain in relation to others. The Jain may decide to always walk bent over sweeping the road so as not to inadvertently kill some tiny insect in his path, but deferring completely to another person is, if anything, an even more impossible project. For such deference would render one without personality - without the very qualities, in other words, upon which one's relations with the other person are grounded. [Rieff, p. 99-100, emphasis mine.]
Rieff writes about the futility of living wholly for another, with another's death always in mind. But his words apply equally to the sad project of living wholly for another in a more literal sense - of hesitating to commit suicide out of concern for others. A life lived out of fear for the harm one's death might do is as awful, and as futile, as a marriage maintained for the sake of the children - a horrible, empty hole which does no good for anyone.