[1] https://www.betterhelp.com/advice/psychologists/what-is-secu...
One thing I will note - if the kid doesn’t sleep and wakes up the adults for years, that impact pretty clearly ruins the adults, and has severe impacts on the kids too.
When you try to expand attachment theory to try to understand healthy kids in non abusive situations the effect size is usually smaller than the experimental noise.
Citation? As far as I know, the roots of Attachment Theory are in the World War II work of John Bowlby, investigating the effects of children separated from their parents when major cities were evacuated during the Blitz.
It is much later that the association of insecure attachment and addiction was scrutinized.
It's something I fully realized only recently, once I spotted my younger daughter sprinting for toys her sister played with, moments after the latter left for kindergarten, and repeating the exact same kind of play she saw her sister do - which was mostly 3 y.o.-level creative reinterpretation and misuse of toys. After that, I started to pay more attention, and noticed that our younger daughter repeats just as many behaviors of her sister as she does of my wife's and mine.
I'm not saying this necessarily should eliminate all worry you have about attachment (personally sleep-training seems like a bad idea to me too; I'm not a parent however), but as far as what research is available, from the OP:
> Of the few studies that have looked at the short- to longer-term outcomes of sleep training, none have found an effect on a baby's attachment or mental health. Hiscock's study, for example, the largest and longest longitudinal study done on sleep training, found sleep-trained children were no more likely to be insecurely attached to their caregiver at six years of age than their peers. (Experts like Hiscock say they aren't aware of any studies that look at potential long-term effects of cold-turkey cry-it-out, just at modified extinction. They also examined healthy babies at least six months old. So these findings aren't necessarily applicable to infants trained at younger ages, or in other ways.)
> Like other longitudinal studies, Hiscock's lost touch with a number of families when it was time for the final follow-up: 101 of the original 326. That means it is theoretically possible that the sleep training did affect some children in either a negative or positive way long-term, but that their experiences weren't captured. It's more likely, though, that any effects of a single intervention simply "washed out" after six years, says Hiscock.
https://www.researchgate.net/publication/230830539_Five-Year...
While this article shreds a lot of studies on sleep training, it goes on to cite a lot of others without evidence of equally scrutiny, so who knows.
I'll also add that different people respond very different to things; maybe for some babies sleep training might have long-term effects, and for some it doesn't. Certainly if I look at my own shitty childhood, me and my brother responded quite differently. He was affected much less than I was.
Pretty smart cat, if you ask me, he also managed to teach our dog to play certain kind of games between the two of them.
I think you'll find out you've had much less of an effect than you think.
There don’t appear to be any.