There is no upper age limit on a person trying to improve their quality of life or their coping skills to deal with it.
Conversely, there is no lower age limit on a person who wishes not to try and would rather end their own life, which requires its own set of coping skills to accomplish.
No toddler is capable of a deliberate hanging and the parents would be responsible, so y'know, unfortunately kids are gonna be excluded from my comments but with the caveat that if a child commits suicide there is undoubtedly something deeply broken whether it's psychological or situational. All things meaningless, I wouldn't put my energy into worrying about things which are that broken except for how to isolate them from society at large in a humane fashion.