Look at how you or other people walk. Then going a bit meta.
This post is probably not high quality enough to deserve to be top level purely on its qualitative merits. However I think the sheer importance of the issue for human well-being makes it so. Please consider importance / potential utility of the whole discussion and not just the post, and not only quality when voting.
Minor depression is not really an accurately defined, easily recognizable thing. First of all there are people with hard, boring or otherwise unsatisfactory life who are unhappy about it, how can one tell this normal, justifiable unhappiness from minor depression? Especially that therapists often say having good reasons to be depressed still counts as one, so at that point you don't really know whether to focus on fixing your mind or fixing your life. Then a lot of things that don't even register as direct sadness or unhappiness are considered part of or related to depression, such as lethargy/low energy/low motivation, irritability/aggressiveness, eating disorders, and so on. How could you tell if you are just a bad tempered lazy glutton or depressed? And finally, don't cultural expectations play a role, such as how Americans tend to be optimistic and expect a happy, pursue-shiny-things life, while e.g. Finns not really?
Of course there are clinical diagnosis methods, but people will ask a therapist for a diagnosis only when they already suspect something is wrong. They must think "Jolly gee, I really should feel better than I do now, it is not really normal to feel so, better ask a shrink!" But often it is not so. Often it is like "My mind is normal. It is life that sucks." So by what heuristic could you tell whether there is something wrong with yourself or other people?
This is heuristic I built mainly on observational correlations plus some psychological parallels. Has nothing to do with accepted medical science or experts opinion. My goal isn't as much as to convince you this is a good heuristic, but to open an open-ended discussion, asking you if it seems to be a good one, and also trigger a discussion where you propose other methods.
How I think non-depressed men walk
"Having a spring in the step." This old saying is IMHO surprisingly apt. I like this drawing - NOT because I think depression is based on T levels, but I think this cartoonishly over-exaggerated body language is fairly expressive of the idea. For all I know this seems more of a dopamine thing, eagerness, looking forward not testosterone.
It seems to me non-depressed men push themselves forward with their rear leg, heels raised, calves engaged, almost like jumping forward. This is the "spring" in the step. The actual spring is the rear leg calf muscle. Often this is accompanied by a movement of arms while walking. A slight rocking or swaying of the NOT hips but chest / shoulders may also be part of it, but I think it is less relevant. The general message / feel is "I'm so eager to tackle challenges! That's fun!"
Psychologically, I think all this eagerly-looking-forward-to-challenges spring in the step means a mindset where you are not afraid of the future, but not because you think it will be smooth sailing, but because you are confident in yourself to be able to tackle challenges and even enjoy doing so. This seems like a healthy mindset.
How I think depressed men walk
Dragging feet. Dragging a slouched, sack-like, non-tension upper body. Leaning forward. Head down. Shoulders pulled up, hunched up to protect the neck, engaging the upper trapezius muscles. A chronic pain in the upper traps (from their constant engagement), when having your upper traps massaged feels SO good, may be a predictive sign of it. Comes accross as embarrassed, scolded-boy body language.
Another way of walking I noticed on myself and probably counts as depressed is the duck-walk. The movement is started by the upper body slightly "falling" forward, the center of gravity starting to go forward, then "catching" the fall by sticking forward a leg, and the foot hits the ground flat, not with the front part of the foot but the whole foot, like a duck.Basically your heels are almost never raised and calves are not engaged much. This would be impossible / difficult if you had a springy step i.e. pushing forward with the rear leg, you would have to raise a heel for that, but possible if you fall forward and catch, fall forward and catch. Often not raising feet high (related verbs: to scuff, to shuffle).
How I think non-depressed women walk
Generally speaking I use the same heuristic for women who seem like they are "one of the boys" type (i.e. those who wear comfortable sports shoes, focus on career goals not seducing men etc.)
But this clearly does not work with all women, for example, that springy step thing is pretty much impossible in stillettoes for example. Rather I think non-depressed women often tend to sway the hips. It is an unconscious enjoyment of their own femininity and sexiness, not a show put on for the sake of men.
I don't really have clear ideas of how depressed women walk, all I can offer is not like the above. When both the eager spring and the sexy hip sway are missing, it may be a sign.
For people of non-binary gender and other special cases: again all I can offer is that if you are non-depressed, you probably have either the eager spring or the hip sway.
Am I putting the bar too high? False positives?
Is it possible that it is a too "strict" heuristic? While I think these heuristics are generally true for peopel who are in an excellent emotional shape, feel confident, love them some challenges, feel sexy etc. this may be possible that this emotional shape is higher than the waterline for depression, it is possible that some people are not depressed and yet below this like, have less confidence, less eager, happy expectation, less self-conscious sexiness or something like that.
Essentially I think my method does not really have many false negatives, but could possibly yield false positives.
Have you seen many cases that would count as false positives?
Meta: why is minor depression so difficult to tell / diagnose accurately?
There are clinically made checklists, but they sound like a collection of unrelated things. Could really the same thing cause you to sleep too much or not enough, eat too much or not enough? Doesn't it sound like Selling Nonapples? Putting everybody who does not have just the perfect sleeping or eating habits into one common category called depression?
For example in the West most people see depression as "the blues" i.e. some form of sadness. But often people don't report feeling sad, but report being very lethargic and not having energy and motivation and that, too, is often seen as depression. Some people are just negative and bitter and not enjoy anything, and yet they don't see it as their own sadness but more like "life is hard". I guess in both cases it is more line internalizing sadness, considering being sad a normal thing, and not really expecting to feel good. (This may be the case of mine and surprisingly many people in my family / relatives. A life-is-tough, survivalist ethos, not fun ethos.)
Then you go outside the West and you find even more different things. I cannot find my source anymore, but I remember a story that in a culture like Mali women generally don't express their emotions, are not conscious of them, and there depression is diagnosed through physical symptoms like chest pain.
Is minor depression an apple or a nonapple? A thing, one thing, or a generic "anything but normal happiness" bin?
I think my walking heuristic does predict something, and that something is probably close enough to the idea of minor depression, but whether it is a too broad tool with many false positives, or whether it predicts only a narrowly specific case of depressions, I cannot really tell and basically I asking you here whether it matches your experiences or not.
What are your heuristics? What would be a low false positives easy heuristic?
P.S. Researchers found a reverse link saying walking in a happy or depressed style _causes_ mood changes. It seems the article assumes everybody knows what walking in a happy or depressed style means. In fact this is what I am trying to find out here!
P.P.S. I know I suck at writing, so let me try to reformulate the main point a different way: we know people cannot be happy all the time and often have such a unsatisfying life that they are rarely happy. How can we find the thin line between being normal common life dissatisfaction based unhappiness (hard or boring life) and minor depression? Can walking style be used as a good predictor of specifically this thin line?