Instead, it should warn the user that their pattern of thinking indicates mental health issues and they need to search for health from a medical professional.
In all of the cases (that I'm aware of), these people were already diagnosed, and the family was aware of their mental illnesses. The awareness and agency you're asking for, from the mentally ill individual, would probably preclude their condition.
If someone is mentally ill, sometimes the only practical protection is to deem them unfit for access by the caregivers or the government (as we do with guns).
The alternative is to assume everyone is unfit, which has its own practical and ethical problems.