Does anyone know much about manic depression?

what age is onset usually?? Can it hit someone at the age of 40? Can it be "brought on" by anything?

Usual onset is between puberty and mid-twenties.

Some people cope with it untreated for a long time, hiding their symptoms, or they think that they just have periods of depression, when in reality, they just have a long cycle between up and down. If something really rotton happened recently, then someone already bipolar could start having stronger or more rapid cycling.

I think, at age 40, especially if this person is female, there are big hormonal changes that possibly could "set off" manic depression, similar to most people having their first symptoms during puberty.

If nothing big has happened to you recently like a divorce, death, or other bad event, then you should check first with a medical doctor to rule out a physical problem, like menopause. Then you should see a psyciatrist, and tell them why you think it might be manic depression, not just depression. The two problems are treated differently, so diagnosing properly is important.

Usually Bipolar or Manic Depression is genetic, but can be brought forward and rear it's ugly head at anytime. It can hit pretty hard usually during hard events in ones life. My husband suffered from Bipolar probably all his life his doctor said, but he didn't get a diagnosis and didn't hit really hard until he was around 36 years old. He had some stressful events happen in his life that triggered a complete nervous breakdown and that is when we finally seeked help.