My point is that many times we are not aware what is it that makes us feel bad and we just build a narrative that could or couldn’t have anything to do with our feelings. A good advice is, I think, when feeling bad; try to change how you spend your time and you can be surprised. Don’t trust too much in introspection.
There's some interesting discussion going on about antidepressants, which is somewhat similar to discussions about add medication for kids. 2 points: (1) Psychiatric diagnosis is often like the BMI, true at a population level but not necessarily true at a personal level. (2) Pathological is relative to the environment to need to live in. If school requires an 8 year old to pay attention in a class with forty 8 year olds for seven hours a day, inability to do so is often the trigger for medication.
With depression, I think it's uncontroversial the environments can play a large role. If the first course of treatment was living better, and medicinal treatment was layered on top of that as needed we would have better results with fewer side effects. OTOH, there are limits to what a doctor can do.
My earlier comment is more about 'why 40 year old men' not 'why depression.' The latter is almost certainly the more important and actionable question though.
This whole "you're special" thing wasn't always here, it's a relatively new thing.
I thought of my own "hard abilities" like talent in math or sports as a fixed thing or more precisely a sort of talent effort equation. I though of the environment (if I get this opportunity) as the determining wildcard. I thought of my own courage, ingenuity and strength of character as inexhaustible wells. If success hinges on my determination and strength of character, success is guaranteed. Just give me the chance. I'll take it from there.
Reality is less rosy. There is a reason we admire (or detest) those with genuinely powerful strength of character. It's rare and valuable.
At 40 (or earlier, later, I dunno exactly) your own part becomes more clear. Your failings are big. They're behind you and ahead of you. You can see them and their causes. What you haven't achieved and your role in it is clear. What you won't achieve and your inevitable role in that becomes clearer.
Failure (again, I think it's relevant that my own experience is as a man), is heartbreaking for a man. It hits us at our core. It shatters our illusions and strips us of what we allow ourselves to think we are.
It's hard being a person. It hurts being a person. It's heartbreaking. It's painful. It really is so much more than we can take, to feel all the pain in earnest.