Mr. Ghaemi writes: "The best crisis leaders are either mentally ill or mentally abnormal; the worst crisis leaders are mentally healthy." Winston Churchill is used as an example of the former.
Many great leaders have been mentally ill, mainly with severe depression and sometimes with mania. This is not an entirely controversial statement. It is generally accepted by historians that Abraham Lincoln had severe depression, and so did Winston Churchill. Both were suicidal at times. Some other figures are less well-known but the documentary evidence is relatively strong: General William Sherman was removed from command because of concerns that he was insane. He appeared, in retrospect, to have experienced a manic episode with paranoid delusions; he also had,throughout his life, episodes of severe depression, along with occasional suicidal thoughts. Mahatma Gandhi and Martin Luther King both made suicide attempts in adolescence, and each had at least two severe depressive episodes in their lifetimes.
This is not to say that all leaders had mental illness. Most leaders did not; most leaders were mentally healthy. And that may be the problem. Mental health may not be as good for leadership as people often assume.
This would be the case if mental illness confers certain psychological advantages that may be useful for leadership. Mania, for instance, is well associated with creativity. Depression, in many psychological studies, is associated with enhance realism. Both may increase resilience. I have reviewed the scientific evidence for the occurrence of these positive aspects of mental illness elsewhere. If this evidence is correct, it may explain why mental illness might enhance, and mental health hinder, crisis leadership.