There is many ways a person which can use to end his life including suicide, euthanasia... The only difference is that you get killed by someone else in euthanasia.
Never will support or encourage someone to end his life instead I will refer him to a psychiatric to treat him (talking about the OP case).
If he has an end stage cancer, painkillers even knowing that they aren't helping a lot, can reduce his pain.
For dementia & schizophrenia they need someone who help them. (not to get ride of them, this only will make the retirement assurance happy).
Finally, should we end a life of a young girl because she suffers during her periods? Someone who has a chronic headaches? ... Next years i think we will hear about theses cases!
Next thing would be we hear about relatives deciding to kill their grandma because she got dementia and can't decide that anymore. Well, that would be eutanasia really. Reminds me on hitler on his "ending unworthy lives".