Insanity is the state of being seriously or mentally ill. It's extreme foolishness or irrationality.
The symptoms of insanity are... Long lasting sadness or irritability,confused thinking, extremely high and low moods, excessive fear, worry or anxiety, nervousness, delusions or hallucinations, denial of obvious problems, and many unexplained physical problems.
Albert Einstein defined insanity as "doing the same thing over and over again and expecting different results."In Macbeth,Macbeth kills multiple people.He kills people expecting to stay king and be in power forever.In the end he ends ups getting himself and others killed.
Today in society we do not call people insane we use the term mentally ill or mental illness(Juanita Hayes). Different people get triggered by different things which cause them to have an "episode".
Mental illnesses like being insane can be caused from several things like for an example your genetics, psychological problems, or brain defects. People can become insane from exprencincs that have caused them trauma and could have made them paranoid. In Macbeth, his was mostly paranoia which caused him to kill people and that would be a psychological problem in this story.