Medically speaking a mental illness is no different than a physical illness.
Mental illness does not have to be severe just as physical illness does not have to be severe.
Sick leave policies typically only require a doctors note/visit if you are absent for multiple days.
Taking a single day off for mild mental illness, something like elevated stress levels causing anxiety that interrupts your sleep, seems perfectly consistent with most of the corporate sick leave policies I have read.
Mental illness does not have to be severe just as physical illness does not have to be severe.
Sick leave policies typically only require a doctors note/visit if you are absent for multiple days.
Taking a single day off for mild mental illness, something like elevated stress levels causing anxiety that interrupts your sleep, seems perfectly consistent with most of the corporate sick leave policies I have read.