The American Journal of Forensic Medical Pathology reports that 80.2 percent of forensic medical experts believe that manual pressure to the neck can cause death due to cardiac arrest. However, a 2011 review in Forensic Science International concludes that traumatic pressure to the carotid sinus isn't enough to cause death.
Manual self-strangulation cannot cause death due to hypoxia, or lack of oxygen, because the victim passes out and releases the pressure before hypoxic death occurs. However, according to a story aired by NPR in 2012, around 82 teenagers are known to have accidentally died from self-strangulation while playing the so-called "choking game" over a 12-year period. All of these deaths involved applying a ligature, such as a belt, scarf or rope, presumably didn't release as intended after the victim became unconscious.