Is it possible to kill yourself by holding your breath?
This question is obviously copied from Quora, but I had heard it as a fact that we cannot kill ourselves by holding our breath and I'm looking for a referenced answer.
Healthy people cannot hold their breaths until unconsciousness sets in, let alone commit suicide.
According to Parkes (2005), a normal person cannot even hold their breath to unconsciousness, let alone death. Parkes says:
Breath‐holding is a voluntary act, but normal subjects appear unable to breath‐hold to unconsciousness. A powerful involuntary mechanism normally overrides voluntary breath‐holding and causes the breath that defines the breakpoint.
Parkes explains that voluntary breath‐holding does not stop the central respiratory rhythm. Instead, breath holding merely suppresses its expression by voluntarily holding the chest at a certain volume. At the time of writing, no simple explanation for the break point existed. It is known to be caused by partial pressures of blood gases activating the carotid arterial chemoreceptors. They are peripheral sensory neurons that detect changes in chemical concentrations, including low oxygen (hypoxia) and high carbon dioxide (hypercapnia). Both hypoxia and hypercapnia are signs of breath holding and both are detected by the chemoreceptors. These receptors send nerve signals to the vasomotor center of the medulla which eventually overrides the conscious breath holding.
The breaking point can be postponed by large lung inflations, hyperoxia and hypocapnia, and it is shortened by increased metabolic rates.
- Parkes, Exp Physiol (2006); 91(1): 1-15
Counterexample: At least some people can train themselves to hold their breath until they pass out, and if this occurs underwater they will almost certainly die by drowning.
When I was in military service I became friends with some U.S. Navy SEALs. They go through a notoriously difficult training and selection process (BUDS) that has been well documented. Among the program's "evolutions" are tests in which candidates have to solve problems to access SCUBA units while submerged in pools or water tanks (and while being harassed by instructors). It is common for candidates to pass out during these tests, because if they surface for air they fail the test. (And these are people who self-select as very motivated to not fail at any cost.) Apparently the tests weed out candidates who are prone to panic as they lose oxygen and can't override their physiological instinct to breath.
I spoke to one graduate who passed out during one such evolution (but succeeded on a second attempt). He noted that after that incident he lost any fear of drowning, because he realized that if he ever found himself in a situation where he was running out of oxygen he would not feel panic and would just fall unconscious before drowning.