Sadness usually lasts a few days. Or it is a sporadic emotion.

That's a wide discrepancy.

You'll be sad a few days after you break up with a boyfriend, and then you'll be sad every time you see his picture for the next few months.

I'll be devastated for a weekend, but I'll be angry every time I'm reminded of him for the rest of my life.

You may be sad when you see pictures from the Jewish Holocaust or the Fukushima disaster.

That's intermittent, but you'll feel it every time you're reminded of those tragedies.

When it's a depression?

Depression is an emotion you feel all the time when you have it.

It's not just sadness, but a down mood that sucks all the life out of you.

That's why depressed people have a high rate of suicide.

Depression tends to suck all the emotion out of someone, making it impossible to feel joy for even other people or any positive emotion.

I heard that depression is anger without enthusiasm.

Some people choose to live in frustrating situations and be depressed instead of doing anything about it, and in those cases, it is their fault.

But there are people with depression based on brain chemistry.

Attack of the killer brain.

A depressed person might be manic in activity to distract themselves or unable to get out of bed.

Or they do everything slowly and methodically but without any passion.

Isn't that bipolar?

Bipolar means someone's emotional regulator is broke.

It alternates between highs and lows, like manic and depressed.

That's pretty wild.

When is sadness or depression?

Sadness seems like it never ends.

It's depression if it hasn't ended in months and you don't have a solid cause like losing your husband or suffering through a horrible, disfiguring accident.

What's the cure?

Talk therapy for some to improve their lives or their outlooks.

Drugs are an option for severe cases, as is electroshock treatment.

It's shocking that's even in use anymore.

At least lobotomies haven't come back in vogue.