So you go directly from 'doesn't warrant a full diagnosis' to 'doesn't exist'? What exactly are you suggesting here? Are you saying it's not a spectrum of symptoms, from mild to severe, and that there is a bucket of people with 'no depression' and a bucket of people with 'real depression'? What is your basis for such a statement?

Otherwise, you're agreeing that there is a spectrum of symptoms, but somehow the symptoms on the milder end of the spectrum 'don't actually exist'?

A diagnosis is different from a prescription. Just because you have a diagnosis of depression doesn't mean you automatically need to take antidepressants; the diagnosis is used as a tool to understand the general set of symptoms you might experience and what the treatment methods are.

Again, depression is not 'abnormal' emotion or 'abnormal' feelings. Neither are the effects of bipolar. They are both 'normal' and entirely natural biological mechanisms, the problem is that those mechanisms are acting to an atypical degree and causing negative side-effects. In many cases the treatment methods are also entirely 'natural', not involving any pharmaceuticals.

Another way to put this: It is normal for someone to become depressed in response to tough circumstances or disappointment. It's normal for someone to get amped up and slightly manic in response to stress or an immediate threat. Those are natural mechanisms.

When the depression or stress response lasts for days or weeks, that is where it starts to enter into territory where a physician might diagnose it as clinical depression, or hypomania, or mania. Again, the problem is not the feelings, it's the duration and magnitude of the feelings - the feelings and physical effects lasting well after the initial triggers are gone.