No one wants to make babies sad. But teaching infants to fall asleep by themselves — and stay down through the night — almost always requires some hysterical crying and its attendant (temporary) sadness. Some say this causes irreparable psychological damage.

There are various forms of "sleep training" (also known as "cry it out"). But whatever euphemisms you might use, the basics go something like this: When bedtime approaches, you take your drowsy-but-still-awake baby and put him down in his crib. You leave the room. And you don't go back for 12 hours. No matter how much he screams. No matter how much he cries. No matter what.

For the less hardcore, there are many gentler methods. But whatever technique you choose, there will be tears — yours and your kid's.

No topic divides parents, pediatricians, and experts on childrearing quite like sleep training. In online forums, moms and dads who admit to having allowed their babies to cry themselves into a slumber, usually guided by one of many books on the subject, are vilified.

But now, new evidence has emerged from a small but significant Australian study, which measured levels of the stress hormone cortisol in the saliva of two groups of babies with sleep problems who underwent some form of sleep training — and a control group who did not. Researchers found that the sleep-trained babies were, in fact, less stressed than the control group. And a year after the initial study, parents of these infants didn't report any more attachment or behavioral problems than the parents of babies in the control group.

This latest confirmation that sleep training is not harmful to babies will act as a reassuring lullaby to some desperately sleep-deprived parents. To others, who say you should comfort a crying baby no matter what, it's just another endorsement of child-abuse.

Teaching a resistant tot to sleep is one of the hardest things I've had to do — and continue to do in heart-wrenching, repetitive waves with my 10-month-old. But I don't regret it for a second.

We began sleep training my oldest, now three and a great sleeper, at around eight months. It worked but she needed constant training "top-ups" as colds, travel, and teething all sneakily undid our hard work. With my son, horrified by the sheer number of wake-ups (up to 12 a night, which did not have a medical cause), we started earlier. But when we let him cry, he did just that. Until the sun came up. So we stopped what we were doing and I began writing hysterical emails to sleep-training "consultants," including one who wanted to charge me thousands of dollars to sleep in my apartment and magically make our baby a great sleeper. This all sounded very weird, so in the end we battled on with our bespoke training attempts, which are, to be fair, riddled with mayhem and inconstancy. "He's got a tooth coming so I'm going to go to him tonight," I'll tell my husband, who's usually too scared to do anything but nod solemnly when I upend our training "plan" on a whim.

Still, I know from having gone through this once that it does get better, and teaching a baby to sleep — even if you're making up the rules a bit — does eventually bring results. Now we have whole good weeks, which allow me to catch up on sleep and even get some non-kid-related work done.

There's also an important point that the anti-sleep trainers rarely address: the very real dangers posed by a poorly rested parent. Because with fatigue comes lack of judgment. On my most zombified days, I've pushed a stroller into oncoming traffic (and pulled it back just in time), let my older kid fall off our bed onto her head, and accidentally taught her to say "f--k you," which exhausted me has no problem yelling at New York City motorists who ignore stop signs. I'm reasonably confident that none of those things would have happened if I'd had seven uninterrupted hours of sleep the night before. I'm also going to take an educated guess that many, many horrible accidents happen, at least in part, because the adults in charge of children haven't slept.

If you don't want to teach your baby to sleep — for whatever reason — that is your choice and I respect it. Just don't tell me I'm a heartless ogre for striving to be alert enough to keep my kids alive.