Which disorder involves extreme swings of mood from elation to depression?

Yes. There is a disorder known as Bipolar disorder that cover it. There is a section that it will cover known as Manic-Depressive. I suggest looking into the symptoms if this sounds like you. However, please remember that you CANNOT self diagnose. The only way to be 100% sure if you have a disorder is to get a psychological evaluation.

If you are interested in that, you can call your doctor. They will direct you to a nearby clinic that will offer psychological testing and which would take you/your family's insurance. Best of luck!