Uh, menopause????
She killed herself because she was going through a terrible divorce, with Robert Kennedy (an ex-heroin addict) who had cut her off financially, who was known to cheat on her throughout the marriage, and who threw his latest relationship in her face. When she opened newspapers, she saw photos of her husband, his new girlfriend, her old Hollywood friends, and her children (!) together. She was about to lose her home - the home she had designed for her family.
She killed herself in the most shocking, public way possible: by HANGING herself. Her family said she just couldn't take anymore of it. The pressure of losing her home and children was too much to bear.
Did you not read the stories about how Robert Kennedy had to go and get a court order to plan the funeral? Her entire family fought him. They held their own private ceremony the following week.
Her suicide was a cry of ANGER, not depression. She did drink too much, but interestingly, her drinking only appeared to become a problem after he left her.
http://www.washingtonpost.com/national/on-faith/author-mary-kennedys-death-a-cry-of-anger/2012/05/17/gIQAxZdtWU_video.html
http://articles.nydailynews.com/2012-05-17/news/31732217_1_bobby-kennedy-mary-richardson-jacqueline-kennedy-onassis