> The key though is that once mental illness occurs, rationality goes out the window. A minor nitpick: In UK law we have the Mental Capacity Act. People must

> The key though is that once mental illness occurs, rationality goes out the window. A minor nitpick: In UK law we have the Mental Capacity Act. People must not be seen as lacking capacity to make decisions just because they have a mental health illness. Even someone detained against their will under section of the Mental Health Act can make decisions about their care. But your point - "People with major depression and suicidal thinking probably lack capacity to make a rational decision about suicide" is true.