Insanity In One Flew Over The Cuckoo's Nest

Is insanity hereditary or is it caused by your environment? I have often found myself thinking this while reading this book. In this book One Flew over the Cuckoo's Nest, it seems that my questions were not answered but multiplied. In society you can see that some people may are born without emotions and empathy and this presents itself as insanity. And in other instances, it seems as if the human brain can only take so much and it results in insanity. Social groups in this book are seen and represented as something they aren't. Three examples are McMurphy, The black male nurses, and the women nurses. McMurphy enters the ward and is automatically suspected to be different from the other patients. McMurphy is seen as the leader to all the other patients because he is strong and stands up for himself and he exudes this
And as one of the patients said about the head nurse, nurse ratched/ the big nurse, “practice has steadied and strengthened her until now she wields a sure power that extends in all directions on hairline wires too small for anybody's eyes but mine.”( Kesey 28-29 ) The female nurses, specifically nurse ratched, have reasons to be as mean unlike the black male nurses, she was in a war and the reason she is so controlling to the men in the asylum is because she wants to get back at them for what men did during the war and the way that they carelessly killed innocent people. She takes her anger out on them because she has a chance to make them suffer like they made her so she takes all the chances that she can get. Nurse ratched is hurt and is holding a grudge on the men, but she isn’t that bad, she does want to help the patients but she doesn’t want them to get comfortable and try to turn on