Any proof that CC doesn't work/is harmful on younger babies?

[Hopefully]

Someone I know extremely well has just announced her intention to do CC - her LO is nearly 3 months old. Baby sleeps relatively well for one her age - feeds 4 hourly at night, I think wants to cluster feed in the evening, but friend thinks she is just being whingy and tends not to feed her before 3 hours have passed unless she is really screaming.

I'm not anti CC per se, in an older child where all other options have been exhausted and the parents are at the end of their tether, but I strongly feel that this baby is too young, and needs the evening/night feeds (friend is planning CC to get baby down at 7 and waking less at night).

I brought up with her (very gently, in a sort of 'oh, I didn't know that was recommended' sort of way) the fact that CC might be damaging to young babies, and she essentially said she didn't believe me, so I was thinking that if I had some links to proper research, I could at least point her in the direction of them if the conversation came up again. Not sure how I can do it without offending her, but hoping the conversation will come up at some point!

i don't have any research to point you to just experience. I did CC on ds1 when he was 16 weeks - pause for gasp of horror. It was under guidance of CommNuresery Nurse and it was because the only other way he would sleep was to suckle on my breast - my nipples were about to fall off.If we rocked him, held him, gave him a dummy he would still scream so we thought we might as well let him scream in his cot with occassional stroke of comfort from us. 16 weeks was the absolute youngest that CNN would recommend this.
I think your friend is bonkers - CC was emotionally very draining for us so heaven knows what it was like for ds1 - we only resorted to it because we were at the end of out tether. 4 hourly feeds is great and will probably get longer once on solid food.

Why love matters is a book (that I haven't read but is supposed to be very good) and includes research about why it can be harmful for babies to be left to cry.

Well, you could point out to her that the idea behind CC is to
remove 'bad' sleep associations whereas what she is doing is simply
denying her dd a feed to force her to go for longer periods without food.

That ain't sleep training.
It rather reminds me of strict routines advocated by one of MN's favourite childless gurus.

What you are looking for is research into the consequences of abandoning
feeding on demand and implementing a strict feeding routine.
Not sure that research exists.

If I were in your shoes I would bide my time and offer her alternatives
IF she finds that the crying does not subside and is getting disillusioned.
It's her kid, I am afraid.

oh you have to get 'why love matters'. Fantastic book - i dare anyone to read it and still go ahead with CC. Apparently the stress hormone cortisol rises in babies/children left to cry, which can cause problems such as high blood pressure in later life.

and its just plain wrong (imho)

Maybe I could read it and leave it lying around!

It's so difficult when you totally disagree with someone about what they're doing, but can't say so without risking a friendship.

Hopefully the opportunity will arise to mention it/the book or something

there is a book "no cry sleep solution" that offers alternatives to CC. i havent used it but have heard its very good. maybe you could get her a copy.