That said, there are attempts in some countries to make euthanasia legal for severe depression. Note here that the emphasis is on legal - firstly making sure it's not on the spur of the moment - but the conclusion (which some may find callous) is that it really doesn't matter if one person decides to end their life, so long as the process is controlled and we have the documentation that it's not the medical system's fault. It's all about legal responsibility. Maybe a bit of humanity thrown in the mix too, but 'humanity' is a loaded and ill-defined term.
I think the real problem comes into play when the process to provide quality long term mental health is faulty (Like most under-funded overwhelmed medical processes).
Another problem and probably the most glaring one is simply greed, bean counters realizing your life ended at a young age is a massive sum of government money saved. Money saved is money earned.
And of course organ harvesting, though I don't think there's a sound moral argument against not harvesting organs so that someone else can live a full life.
Sadly the fact is we don't live in a world where the 99% have access to any form of legitimate long term mental healthcare, so I feel like implementing that idea in the state our world is in is a slippery slope to something much darker.