Ok to let babies cry themselves to sleep?

Came across this study (a small randomised control trial) that tested (a version of) this question.

Basically, they say it's fine. (well, a "gentler" version -- where parents don't completely ignore babies, but wait a few minutes before checking in on crying babies)

The researchers compared two techniques (to put babies to sleep):

• (A) "graduated extinction" (parents wait longer and longer before responding to a baby's cries)

• (B) "bedtime fading" (bedtime is gradually moved later)

• [and a control group, where parents were given basic information]

They were trying to test whether method A (graduated extinction) was harmful (since you let the babies cry by themselves).

Their main conclusion (from the credo summary):

both graduated extinction and bedtime fading led to babies falling asleep faster. The graduated extinction group also woke up less during the night and spent less time awake after falling asleep.

...

After one year, there were no differences between groups in children's emotional or behavioral problems, and no differences in how securely children were attached to their parents