I looked up what the dementia/amnesia is (aka called soul leaving syndrome/离魂症) would be schizophrenia in today's terms

(ps the ml might also have symptoms of other mental illnesses as well such as pstd due to the trauma/experiences)

https://baike.baidu.com/item/%E7%A6%BB%E9%AD%82%E7%97%87/8261795#:~:text=%E7%A6%BB%E9%AD%82%E7%97%87%E6%BA%90%E7%94%B1,%E5%BD%B1%E8%A7%86%E5%89%A7%E4%B8%AD%E9%A2%91%E7%B9%81%E5%87%BA%E7%8E%B0%E3%80%82 

Thanks for that information 

This is helpful, thank you. I was confused about the snow triggering "bloodthirst."

Soul leaving syndrome is the direct translation of 离魂症. As funny as it sounds, that's an ancient way of calling such syndrome. Modern term should be hypotermia, leading to unconsciousness and hallucination, and yes, it will lead to death. And when he hallucinates under such circumstances, he will see all his childhood trauma.
This is why XW is so afraid of cold.

I believed it calls PTSD (Post st-traumatic stress disorder) is a mental disorder that develops in some people who have experienced a shocking, scary, or dangerous event. This's not just affecting military combat service  members but also anyone, just like what Xie Wei experienced in young age.

 Xtinew:

I believed it calls PTSD (Post st-traumatic stress disorder) is a mental disorder that develops in some people who have experienced a shocking, scary, or dangerous event. This's not just affecting military combat service  members but also anyone, just like what Xie Wei experienced in young age.

This sounds like a better explanation.  Was the scene mistranslated between Jiang Xue Ning  and Xie Wei.