Firstly, to define insane; insane is a spectrum of behaviors characterized by certain abnormal mental or behavioral patterns. I do think that our genetic dispositions were endowed with us when we were born and this is cannot be changed. Those people were feeling very emotional all the time. Some of them were easy to get angry, for more serious situation they may get mood disorder or mental disorder. For people were experiences ones childhood or adult life and lead to madness.
This one we may also call PDSD (Post Traumatic Stress Disorder). PTSD is believed to be caused by experiencing any of a wide range of events which produces intense negative feelings of fear, helplessness or horror in the observer or participant. I think they may do something horrible than the former. When there something stimulated them, they will do something that is unpredictable, such as screaming or cry. But both two types of people got one things are osculate. They all think that they are not mad and insane.
When we watch movie or on TV, there are lot of story about mad person. I remember that I had seen a movie few years ago. Its about a man who saw a murderer kill his whole family when he was a kid. But he just saw the murderers nail polish was red color. When he grows up, get to the age to leave the orphanage. He planned to revenge his family. Then he started to kill people who apply red nail polish. And cut their finger off after killed them. Since he think this is very beautiful. And this is a true story.
For the criminal psychology, this is one kind of satisfaction for those people. People who experiences in ones childhood or adult life lead to madness will always do something to supplement their mind.
To conclude, I think both genetic disposition and experiences in the past will lead a person to madness. However, the reactions of the latter one were more serious than the other one. But for these two types of people wont commonly admit that they were mad.