Another cause of headache is oxygen deprivation, kidney, liver 126.96.36.199 (talk) 00:10, 31 August 2012 (UTC)
Are you certain? I would love to hear a source. Carbon monoxide poisoning and high CO2 are more likely gas-associated causes of headaches. Kidney disease can cause headaches through severe hypertension, and liver disease through hepatic encephalopathy or haemorrhage, but I wouldn't say that these conditions invariably cause headaches. JFW | T@lk 13:20, 31 August 2012 (UTC)
I think the oxygen deprivation cause is a commonly held notion, and likely has basis on reality. There is even a term, turtle headache. It supposedly can be brought on by sleeping completely under bed covers. It isn't surprising given that oxygen deprivation is a stressor on the body.
It may be that headache evolved as a warning, telling the animal, "You are living unhealthily: stop it."Joseph Meisenhelder (talk) 15:27, 6 November 2013 (UTC)
It would be helpful to mention that primary stabbing headaches are commonly known as "ice-pick headaches." I get them, and -- concerned that they might be symptoms of a serious underlying condition -- tried some online research. I had no idea what such headaches were called, but I figured that anyone writing about them would say that it feels like your head is being stabbed with an ice pick. Indeed there were many search results about "ice-pick headaches," and one of those finally told me that the correct medical term was "primary stabbing headache." Ideally such searches would more directly lead to this Wikipedia article and some appropriate mention of the term. AmigoNico (talk) 08:38, 7 April 2013 (UTC)