crash and burn - it might help (if you decide to tell them) to find some articles on the internet explaining exactly what depression is (frequently a chemical imbalance in the brain) and what the symptoms are - that might give you an opening to start a conversation about exactly what you are experiencing. I think sometimes when parents are shut off to the concept of depression or think things like it is "just for spoiled" kids it is because they are hiding their fear that somehow they played a role in it.
My friends daughter was suffering from severe depression and my friend wanted her to "just get over it". It wasn't until I shared some of my "stuff" with her that she really began to understand. Even now 10 years later, her daughter is happily married with a baby on the way, my friend says - I don't know what I would have done with her if I hadn't talked to you.
Some of it truly comes from not understanding and some of it comes from not knowing how to help...I think it would be great if you could share even a little bit with your parents - it might help ease the burden on you a bit.
Keep us posted, okay?