Grayson, right? He, like Phalen grew up in situation where the mercenary unit was an extended family. But it was a family. There was emotional support. The majority of soldiers in the IS grew up in family homes. In many cases it was expected that they go into the family business, but that's different from Clan sibkos. There is threat/pressure against deviation. Your father may never forgive you for going law school rather than the Nagelring. Most soldiers in IS militaries also grew up with other children. On "Bring your parent to school day," they got to see that Sarah's mom is a doctor, and Billy's dad is a dance teacher, and Lee's mom is a firefighter. They spent time in their friend's homes and saw that there are alternatives to the Nagelring and LCAF. People who wash out of the academy will have a difficult transition if military service was a life long aspiration, but they can look around an see people having lives and being happy.
Clan warriors are told from the moment they can comprehend speech that there is only one acceptable path. Think about the story of the college dean addressing the freshman class. "Look to your left, look to your right. One of those people won't be here in 4 years." Imagine getting that speech at 4 years old. In that world, failing out and going to another caste is as bad as dying, probably worse. When IS kids are afraid of bombing a history test and getting grounded, Clan children are afraid failing a trial, and washing out. To have their codex stricken. To never have a chance at a line in the Remembrance.
Most sibko washouts will probably find a life form themselves in the other castes, and many will probably be happy. But while they are still in the sibkos, they live in constant fear. Once they test out, most warriors know they are destined for solhama units.
Going back to the the IS example, members of house or local militaries know that they can serve their time, provide for a family, and eventually retire. Mercs dream of a couple big jobs that let them retire like kings, but if they've saved, and invested, they have a nest egg and they can retire to some planet and open a general store. Others can look forward to gigs at defense contractors or teaching positions at local military academies.
Uh, with respect, none of this is what makes for what is usually meant by the term "child soldiers." It isn't a question of communal vs. individual family child-rearing, or their future retirement plans (which, it must be said, seemed to consist of dying when it came to the GDL, lol). It's about the effect war -- actual war, not training -- has on children and the personalities produced by such an environment. It would be not
quite the opposite of a typical Clan warrior, but certainly nothing like the Clans of BT. For one thing, social mores and stigmas? Those aren't nearly so powerful tools of social control for child soldiers, so forget about zell, dezgra or batchalls. People play up the "might makes right" aspect of the Clans, but in a situation where you're dealing with people who
really believe that, the nukes would've long since come out, with the offending party daring anyone else to speak a single word of protest. Turtle Bay wouldn't have been something that shamed the Clans (causing them to bid away all their warships from that point on) and reduced the Smoke Jaguars' standings amongst the other invading Clans; it would have been a lively-but-not-especially-noteworthy Friday night.
Also, regarding self-medicating: the books go out of their way (across authors too, that I noticed) to mention that Clan trueborns tend to be light drinkers, whereas freeborns in the book Bloodname went out of their way to get hammered constantly, just because trueborns tend to be (as written) uptight control freaks, even the good ones like Trent. Elementals might have some addiction issues with the combat drugs they are injected with, but maybe not.
One issue I'd expect to see a lot more of is stuff like degenerative brain conditions associated with constant impacts. Neurohelmets might as well be afros for all the protection they apparently provide and mechwarriors get dinged around constantly from hard jumps, drop deployments, getting punched in the head, their ride toppling over, etc. Elementals, with less mass to absorb the impacts, should be getting a fair bit of joint/bone wear and tear from the day-to-day operation of their suits and the requirement in combat to land on a quite hard surface with minimal prep. We're talking the same kind of strains and sprains you'd get jumping from a trampoline onto a rocky slope. Combined with their size, it could get ugly...