Many sources of depression stem from feeling trapped with no way out, or to be controlled in such a way that's counter to their sense of self (they feel out of control and unable to influence their own destiny, leaving an unfillable void at the center of their emotions) -- suicide often becomes a way for the individual to assert their self and grant themselves agency in these circumstances.

I've had combat explained to me like this. Imagine you're out in the world one day, grocery shopping, and a guy starts threatening you in the parking lot. In the normal world, you call the police or defend yourself if you need to, or get in your car and drive away. But your options are significantly limited. This problem or situation has other possible outcomes, but society has put artificial constraints the eliminates several effective resolutions.

A soldier in war has far fewer constraints. If some guy is bothering them, they can simply kill that person and resolve the issue. Or they can run them over in their armored vehicle, or bayonet them, or beat them with their rifle until they stop moving. An entire world of options opens up that allows you to simply resolve conflicts -- even if these resolutions are frowned upon in the normal society. Society sets up all these lines you can't cross, except in war you can cross all over them.

There's thousands of these kinds of issues in warfare, where normally impossible issues suddenly become trivial. Need to get from point A to point B? Steal a car. Need to get information from a guy? Beat him till he talks. Building in the way? Blow it up.

When a solider returns home, suddenly these societal restraints are locked back on them. You're suddenly told that you can't cross these lines anymore. But as anybody who's engaged in any kind of social line crossing can talk about, it's hard to roll that back once you've done it. As a result they feel trapped and disempowered. Having previously had literal power over life and death, you're suddenly trying to figure out how to fight with a soccer mom and her kids over a parking spot at the mall -- and you're trying to keep yourself blocked in by lines you now know aren't really there.

In combat you could just declare the minivan a threat and open up the 30 cal. Here you might have to go find another spot.

I'm dubious. A soldier in a war zone spends 98% or more of his time exclusively in the company of his fellow soldiers, whom he most certainly cannot kill or assault without facing extremely dire punishment. Even when he is in combat, he is only there under very strict orders and does not have very much freedom to do anything other than follow them.

That's interesting, but what's puzzling me the most is how less people commit suicide during a war.

If the first step to suicide were ideation, which is usually the result of prolonged psychological isolation, then wartime simply can't provide the proper enviroment for it.

During a war everyone huddles together trying to survive, and social and familial ties could become strong enough that even the thought of suicide would seem offensive, as if one were abandoning friends and family to their own luck. And when you have people running around shouting orders, bullets flying and bombs falling there's simply not enough time to think about anything else.

What people seem to dread being is left to themselves, not their conditions. Which is why only reason why war has ever had any defenders, aside from bureaucrats: it gives "purpose" to men.

Recently enough, Ars ran an article on a study (10.1126/science.1250830), which I'm not sure how appropriate is to the discussion of suicide, but sums up this point quite well:

In 11 studies, we found that participants typically did not enjoy spending 6 to 15 minutes in a room by themselves with nothing to do but think, that they enjoyed doing mundane external activities much more, and that many preferred to administer electric shocks to themselves instead of being left alone with their thoughts. Most people seem to prefer to be doing something rather than nothing, even if that something is negative.

> That's interesting, but what's puzzling me the most is how less people commit suicide during a war.

Just speculating, but, I can immediately see two obvious potential contributing factors to lower suicide statistics (one of which isn't actually about reduced incidence of suicide, per se): during a war, there's a lot more opportunity for suicide-that-doesn't-get-categorized-as-suicide, and there is also a additional opportunity (compared to peacetime) for things that provide short-term, immediate purpose even if they don't deal with the underlying problems.

Total guess, but:

Depression and anger are linked, and when I've been depressed it's often manifested as anger at myself. Sometimes, finding an outside focal point for anger can offer relief from depression. It is easier to find a focal point for anger that other people share, and war can be a common enemy for a large population.