How is it diagnosed?

Usually by filling out a card that asks you creepy questions like "do you dress nicely in front of males/females". Of course they are asking about sex drive, but they seem to insist on wording it like this for some twisted reason.

If you get so many points then you are officially depressed.

This is how gp's do it in my country.

They will ask how you have been feeling in the past 2 weeks because sometimes depression of whatever sort comes as a bolt from the blue.

Other times it is something that worsens over years.

I can totally relate to memory problems, as when I was at my worst I could barely form a coherent sentence. I took a year away from uni, tried a few prescription drugs, but eventually decided that self therapy would aid me the best. My own work has paid dividends.

The drugs did pick me up, and I usually sided with serotonin reuptake inhibitors with neuroleptics, but that is a long, complex and boring story.

In the end you have to find your own path if you feel you are having problems, whether it is officially depression or not.

This is not to say that a good therapist can't guide you.

Good luck.