An intriguing study just published in the Journal of Forensic Sciences ponders current theories in light of historical research which has attempted to answer the question.
In fact, we know so little about the exact mechanism of death from hanging that studies from the 1800s are still some of our best sources of information.
To remedy this, a research group now been formed with the grim task of studying videos of hanging to try and see determine which of the traditional theories might be correct: death by asphyxiation, by stopping blood to the brain, or by the heart stopping after stimulation of the nerves running through the spinal cord.
From the article:
In cases of hanging, the exact mechanism leading to death has yet to be elucidated. Most of our contemporary knowledge is still based on writings from the end of the 19th and the beginning of the 20th century. This article reviews the historic experiments that shaped our current theories. Medico-legal textbooks written in English and French from 1870 to 1930 were reviewed. Various animals, such as rabbits, mice, and dogs, have been used to develop animal models of hanging.
Limited human studies on cadavers and judicial hangings have provided some additional insight into the pathophysiology of death by hanging. The main pathophysiological theories described were respiratory asphyxia, interruption to cerebral blood flow because of occlusion of vessels in the neck, and cardiac inhibition secondary to nerve stimulation. The relative contributions of each of these theories to death in cases of hanging is still debated today.
Recently, filmed hangings have been used as a powerful tool in understanding the pathophysiology of human asphyxia. The Working Group on Human Asphyxia (WGHA) was formed in 2006, and since its creation, 8 filmed hangings have been analyzed. Observing the videos reveals that loss of consciousness occurs quickly, followed by convulsions and a complex pattern of alternating phases of decerebrate and decorticate rigidity. The videos also demonstrate some auditory evidence of persistent air passage through the airways during the hanging process.
The study of the WGHA has provided interesting new insight into the pathophysiology of asphyxia by hanging. Before these new developments, most of our contemporary knowledge was based on writings from the end of the 19th and the beginning of the 20th century.
Tempted to join the Working Group on Human Asphyxia? Fear not, membership criteria are given in the scientific paper:
“It is known, however, that some hanging victims film their hangings, mainly in an autoerotic context…. Each scientist who has such a video or who has access to such a video is welcome to join this group and the video will be added to the ongoing study.”