What drives humans to suicide?

The book i read was The Bell Jar. My big question is what drives humans to suicide. This book is about a girl who is depressed with her life. There are a great number of things that drive people to suicide. Theres pressure to society to be the certian image they think is best, like being a size 0. There's stress with many important things you have to worry about in your life, like maybe your job, money, family ect. In the bell jar, she was just overall depressed about her life. She was living on an all paid internship in New York, and she still wasent happy which isnt right, any girl would kill to be in her shoes. She didn't really have any reason to be depressed, sometimes you don't really need a reason to be sad. When you have depression, there's a certian chemical in the brain that doesent function right. Esther tried killing herself because she wasent happy with how her life was going, and she just wanted to end it all. She thought she was going to be alone for the rest of her life and never find love. Esther tried drowning herself, cutting herself and took a lot of pills which made her overdose, after trying to kill herself she had to stay at a mental institution. I think the pressure of life drives humans to suicide. Some people just can't take all of the responsibilities they have to worry about, and it overwelms them to the point where they just can't take it anymore.