@ebveloz So I liked this podcast, which interviewed a researcher which basically asked this same thing: What happens to babies who aren't sleep trained or for whom sleep training doesn't work:
https://podcasts.google.com/feed/aH...d=0CAUQkfYCahcKEwj4nb658ID9AhUAAAAAHQAAAAAQeQ
Sorry for the monster link. You could just follow the jump to the actual researcher and her work if you don't want to listen to a podcast.
Anecdotally/my experience: - I have three children, the eldest of whom is 14. I didn't use extinction methods with any of them. I do not consider them to be bad sleepers, I consider them to be normal (except maybe the middle one, he never really did longer stretches at all until I night weaned him at 2.5yo) but going by your definition of having parent-led sleep associations, yep, I pretty much fed them to sleep and back to sleep at every wake until they weaned.
I fed my first child on demand including at night until he stopped of his own accord (around 2.5 years), I fed my second on demand including at night until I got pregnant and my husband and I decided we did not want to bedshare with an infant and toddler at once, so I got stricter with myself about bringing him into our bed, which I had generally done for my own comfort/convenience between the ages of 1-2 years. He was 2y3m when I started and 2y6m when the process was complete, I did not follow a method I just kind of made it up - a combination of this "parent training" not letting
myself bring him into bed, plus a delay before nursing, plus early unlatching at an earlier and earlier point, plus changing nursing associations to a specific side and avoiding that side. My youngest is currently 17 months and around 1 month ago I decided to try the method that worked with my second child now, despite him being a year younger, since I don't see any benefit of waiting. So far so good, it's slow progress, but that's OK with me.
Going by the anecdotal received wisdom of the AP/anti-sleep-training community, it's normal for babies to wake and feed at night and they will stop this by themselves somewhere between 18 months to 3 years. This was my experience, and that of my friends who did similar (but small sample size). After that, they are totally normal - there's no difference I can see between children sleep trained vs children fed to sleep until self weaning. My eldest has ADHD, but the research evidence suggests ADHD is not caused by parenting but is likely genetic. I have ADHD too, and my ex/his dad has some significant hyperactive traits, so genetics seem likely.
IME the bedtime feed was the last to go, feeding to sleep at the start of the night did not make them keep waking at night once they had got to the point they were naturally sleeping through. And I have stopped and started in my slow sleep training many times, tend to give in as soon as there is any protest, it doesn't make things go backwards as the sleep training literature suggests. Sleep training is based on behaviourism, and I think behaviourism is incredibly flawed, so it never made sense to me to follow it for sleep.
AP theory (honestly, not sure how evidence based this is) suggests that in bedsharing and feeding to sleep, you build security and trust and confidence and the baby/child will simply move on when they are ready. It was important to me for sleep to be a safe and comforting thing, bedtime to be a happy and calm association. I remember my little brother being terrified of bedtime because he was left to cry alone. I didn't want that (I recognise, especially with hindsight, that this is not illustrative of all sleep training!)
Disclaimer: I understand that bedsharing particularly before the age of 4 months carries increased risks in comparison with room sharing on separate surfaces. I'm not suggesting this as a blanket policy, just sharing what I did. You should look into the risks before you bedshare.