but also "optimistic about the future", "energy to spare", "feeling good about myself", "interested in new things", "feeling cheerful". How many depressed people could plausibly rate themselves high on those? Having no energy, being pessimistic, not interested in anything, and feeling bad about yourself are... pretty classic symptoms of depression, though I don't know what the exact clinical requirements are.

In the absence of a blood test that can report "you're 79% depressed, we have to rely on self-reporting. Which is error prone as the scales are highly individual.

As I understand it, and someone correct me if I don't, these self-reporting scales are just a loose diagnostic indicator. They're more useful over time, especially if receiving therapy or medication, as the change in responses can be tracked.

Right, sure, but the study treats well-being and symptoms of depression as separate things.

But if well-being is stuff like being optimistic and fulfilled, then it seems to me hardly a surprise that being optimistic and fulfilled makes you less likely to become depressed, in the same way that not being depressed today makes you less likely to be depressed tomorrow. So I'm trying to work out what this study is actually saying, other than non-depressed people (with ASD) are less likely to be depressed in the future than currently slightly-to-very depressed people.

What does it mean to score very poorly on this?

My therapist uses a different questionnaire that has more negative questions like "Little interest or pleasure in doing things" or "Poor appetite or overeating". I tend to do alright on that one.

However, I score over 2 on only a few of the items on the list you posted, and a lot of them are solidly 1. There's a feeling of tension, anger, and frustration I just can't shake.

There's a big difference (to me anyway) in the wording between "Feeling bad about yourself – or that you are a failure or have let yourself or family down" and "I’ve been feeling good about myself"

I wouldn't say that I feel like a failure (and I have nobody who cares enough to let down), but I sure haven't been feeling good either.

I don't know quite how to express this doctors and mental health professionals in a way they understand, though, and this scale really kind of illustrates it for me, so I'm wondering what that means?

I don't have specific advice regarding the score, but I do suggest any advice provided here be taken with a grain of salt. Not because of the community (I like to think we're all well-intending here, it isn't about that) but because we're simply strangers, and we don't know enough about you to provide an accurate answer.

Find a good mental health professional who will take the time and care to understand you, and show them the same thoughts you've shared here.

You shouldn't have to change your vernacular with a mindful professional. There's plenty of leads they can follow here -- And if you want effective answers about your feelings, that's who should be doing it! A true professional dedicated to figuring these things out with you.

The questionnaire you're describing is the PHQ-9. It's the industry standard screener for depression.