This is the research companion to Bedtime Started Longer Ago Than You Think. Read the main post first.
The main post argued that much of what decides how bedtime goes is upstream of bedtime itself, in how many nights a week the routine happens, in what parents believe a waking baby needs, in the day the child brings to bed, and for some families in a work schedule nobody at home controls. Here's what that rests on. Two sources are about routines, one a large survey and one a randomized trial. One follows mothers' beliefs from pregnancy through the first year. One is a tiny experiment with a skipped nap. One looks at parents' shifts and older children's sleep. They cover different ages and different designs, and we've kept those separate below. Most samples are educated, mostly white, and from families in which children sleep in their own beds.
Nights, Counted
Mindell, J. A., Li, A. M., Sadeh, A., Kwon, R., & Goh, D. Y. T. (2015). Bedtime routines for young children: A dose-dependent association with sleep outcomes. Sleep, 38(5), 717-722.
DOI: 10.5665/sleep.4662
What they found: In an internet survey of 10,085 mothers in 14 countries and regions, with children from birth to five (7,499 babies and toddlers, 2,586 preschoolers), more nights a week with a bedtime routine went step by step with earlier bedtimes, falling asleep faster, fewer and shorter night wakings, and more sleep. Mothers who said their child "never" had a routine described a sleep problem 47 percent of the time for babies and toddlers and 39 percent for preschoolers; with a routine every night, those figures were 23 and 15 percent. Preschool daytime behavior problems fell from 23 to 9 percent across the same range. The pattern held in both predominantly Asian and predominantly white regions, though consistent routines were more common in the latter.
Why this matters for you: It's the basis for counting nights instead of rating them. The effect was graded, a little better with each extra night, rather than a line you either clear or miss.
What it doesn't answer: It's a single cross-sectional survey, and the authors state that causal interpretation can't be made from it. They raise their own alternatives. A routine may mark a cluster of other sleep habits, its absence may mark household chaos, and an easier child may make a routine easier to keep. Everything was mothers' report, infancy routines were recalled, the sample skewed toward educated mothers, and nobody asked what the routines contained.
Guidance in the First Year
Paul, I. M., Savage, J. S., Anzman-Frasca, S., Marini, M. E., Mindell, J. A., & Birch, L. L. (2016). INSIGHT responsive parenting intervention and infant sleep. Pediatrics, 138(1), e20160762.
DOI: 10.1542/peds.2016-0762
What they found: In a randomized trial of 291 first-time mothers (279 analyzed), nurse home visits starting around three to four weeks after birth included sleep guidance (short, consistent bedtime routines, putting the baby down drowsy but awake, not feeding as the last step before bed, and alternatives to feeding back to sleep). Compared with a home-safety control group, more guidance babies were in bed by 8 pm (46 versus 24 percent at 16 weeks; 66 versus 47 at 40 weeks), more were put down awake (35 versus 16 percent), fewer were fed back to sleep after waking, and they slept 22 to 35 minutes longer at night at 8, 16 and 40 weeks.
Why this matters for you: It's the trial evidence that what parents do before bed can be shifted, and that babies' night sleep moves with it, at least for most of the first year.
What it doesn't answer: By one year the two groups' night and total sleep had converged, and the guidance never reduced how often babies woke or fed at night. All sleep outcomes were mothers' reports, which matters when the questions line up with what the guidance taught. The families came from one Pennsylvania hospital and were mostly white, married and college-educated. The comparison was guidance against no sleep guidance, not one sleep method against another.
Beliefs Before Birth
Tikotzky, L., & Sadeh, A. (2009). Maternal sleep-related cognitions and infant sleep: A longitudinal study from pregnancy through the 1st year. Child Development, 80(3), 860-874.
DOI: 10.1111/j.1467-8624.2009.01302.x
What they found: Eighty-five Israeli women expecting their first child rated short vignettes about infant night waking in the third trimester and again at 1, 6 and 12 months. Beliefs emphasizing infant distress and the need to soothe predicted more night wakings at six months, measured partly by a wrist-worn activity monitor; beliefs emphasizing limits on nighttime help predicted more consolidated sleep. From six to twelve months, about 54 percent of the belief-to-sleep link ran through how much parents soothed their babies at night. The link also ran the other way, with more waking at six months predicting a later shift toward the limits view.
Why this matters for you: It's the evidence behind the Consider This. What you believe a waking baby needs is measurable before the baby exists, and it travels with how the night goes.
What it doesn't answer: It's correlational, and both the beliefs and some of the sleep data came from mothers, so shared reporting can inflate the links. The sample was middle-to-upper income, first-born, healthy babies sleeping on their own; the authors themselves call for testing in other cultures and income levels, and they warn that "it would be wrong to conclude from these findings that parents should abstain from approaching their infants at night." Temperament wasn't analyzed, and it doesn't speak to families who share a bed.
One Skipped Nap
Berger, R. H., Miller, A. L., Seifer, R., Cares, S. R., & LeBourgeois, M. K. (2012). Acute sleep restriction effects on emotion responses in 30- to 36-month-old children. Journal of Sleep Research, 21(3), 235-246.
DOI: 10.1111/j.1365-2869.2011.00962.x
What they found: Ten healthy toddlers aged 30 to 36 months, kept on a strict sleep schedule for at least five days before each test, were assessed at home after a normal nap and after a skipped one. On the no-nap day they showed 34 percent less time in joy and pride on a solvable puzzle (d = .77), a 31 percent increase in worry or anxiety when asked to finish an unsolvable one, and less of the confusion that signals engagement with a hard problem.
Why this matters for you: It's a small, careful look at the day a child brings to bed. One missed nap changed how toddlers met a frustrating task, before bedtime came into it at all.
What it doesn't answer: Ten children completed the analyses (from 78 screened), and they were unusually good sleepers by design, so it can't say how typical toddlers or chronic short sleep would look. It tested one missed nap, not nighttime sleep or bedtime behavior, and children varied a lot in how they responded. It doesn't reach older preschoolers, and it isn't a study of bedtime resistance.
When the Schedule Isn't Yours
Logan, A., & Schneider, D. (2025). Parental exposure to work schedule instability and child sleep quality. Work, Employment and Society, 39(1), 64-90.
DOI: 10.1177/09500170241235863
What they found: In a survey of 3,760 hourly service-sector parents at 97 large US companies, weighted to national benchmarks, each kind of schedule instability (on-call shifts, last-minute changes, cancelled shifts, less than 72 hours' notice) was independently linked with worse child sleep by parents' report. Among the most exposed families, 49 percent of children didn't sleep about the same amount each day, against 32 percent among the least exposed. About 35 percent of the link ran through work-life conflict, parental stress and wellbeing, and material hardship, rising to about half when children's behavior was added.
Why this matters for you: It's why the main post treats some uneven bedtimes as a scheduling problem the parent doesn't control. Parents' stress carried a large share of the link, which is a reason for kindness toward yourself, not a new task.
What it doesn't answer: The median child was eight, so this is school-age evidence, not a study of babies or toddlers. It's a single snapshot from parents recruited through social media, with sleep reported by the same parents, so it can't establish cause or rule out other differences between families. The behavior pathway may run both ways, and it covers US service-sector workers only.
Coming Up
When everything a child does gets graded, by teachers, by coaches, by us and eventually by the child. Next time we look at evaluation and self-evaluation, and at why the answer isn't another praise recipe.
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