What Is Known from Science
A person's reality is what that person believes in.
"Voodoo death" (Walter B. Cannon, 1942). The American physiologist described cases of Aboriginal people and Maori who, after breaking a taboo or becoming victims of "bone pointing", died within a few hours or within a day. Autopsy found no organic cause; Cannon linked the deaths to an acute adrenaline reaction of fear.
"Psychogenic death of Mr J" (1979) - A 37-year-old man died within a day after he decided that spinal surgery had "doomed" him; the autopsy found no pathology.
"Hex death" (C. K. Meador, 1992) - A patient with minimal stomach cancer fainted and died right after the doctor's words that he had "little time left to live". The author showed that fear, supported by authority, can start a deadly nocebo effect.
Stress cardiomyopathy ("broken heart syndrome", Takotsubo syndrome). A sharp emotional shock (loss, quarrel, even winning the lottery) causes sudden weakening of the left ventricle, irregular heartbeat, and shock. In rare cases this ends with heart rupture and death, even without narrowing of the coronary arteries.
"Give-up-itis" (passive loss of the will to live). Documents about prisoners of war from the Korean War, prisoners of concentration camps, and shipwrecks describe stages: social withdrawal -> apathy -> refusal of food and water -> heart stops in 2-3 weeks. Neuropsychologist John Leach links this to a lack of dopamine in frontal-striatal circuits. Loss of hope and complete loss of purpose suppress the limbic and prefrontal circuits that control initiative and breathing.