There's online tests that you can take to see if you're suffering from symptoms caused from depression and what not. Sort of like the same tests that you would take at the doctor/therapist's office. They aren't so in depth though.

most of us have been dianosed by doctors/therapists.

If you have these mood swings please have an appointment with your doctor and talk to them about it.

none of us have to pass a spelling test though LOL

I had all the symptoms of depression. Plus, normal things that I used to enjoy weren't enjoyable anymore. I became a hermit. I stopped going to classes. I lie to everyone about how I'm doing. And the point at which I knew I had to seek help immediately came when my dad asked me about my travel plans home for Christmas break, and I realized that I didn't give a rat's ass if I ever left my apartment ever again, let alone fly home to see my family and enjoy the holidays. I somehow found the strength to call my campus's counseling services center and make an appointment, and I was diagnosed with major depression and anxiety disorder. I mean, I knew I was depressed before then, but it didn't really hit me until my conversation with my dad.

You can find resources and tests online that will help you identify possible symptoms you have that may be caused by depression. If you fill one out and bring it with you to your doctor, you can start figuring out if you suffer from depression that way.

Severe mood swings could be bipolar. I agree that the online tests are a great place to start before you make an appointment to see a doctor or therapist.

Beware of taking an anti-depressant only w/o a mood stabilizer if you are bipolar it could throw you into mania.

Here is one of the many online test for depression:

http://www.med.nyu.edu/psych/screens/depres.html

i think getting a formal diagnosis is best. i think i always knew i was depressed, even before my diagnosis. i was always accused of being overly sensitive and of overreacting. if i got in to an argument with my family, i'd not answer the phone for days and live like a hermit in my apartment. it's different for everyone, but sometimes, extreme reactions to mundane events can be a sign of depression.