It can become one. Yes. When GAS are the only solution to prevent depression and suicide, then yes, it becomes a basic need.
Even in the most fringe cases, I cannot agree that it is a neccesity for survival in any sense of the word if depression is the symptom you're arguing.
That is not to say depression isn't real, or to discredit the struggles of having to deal with it - but there are certainly ways of working with it that doesn't involve irreversably altering your body.
Though if someone who is of legal age has gone through consultation with the implications of such a surgery still wants to go through with it - more power to them.
