Today, mothers of newborns find themselves confronting a common dilemma: Should they let their babies "cry it out" when they wake up at night? Or should they rush to comfort their crying little one?
In fact, waking up in the middle of the night is the most common concern that parents of infants report to pediatricians. Now, a new study from Temple psychology professor Marsha Weinraub gives parents some scientific facts to help with that decision.
The study, published in Developmental Psychology, supports the idea that a majority of infants are best left to self-soothe and fall back to sleep on their own.
"By six months of age, most babies sleep through the night, awakening their mothers only about once per week. However, not all children follow this pattern of development," said Weinraub, an expert on child development and parent-child relationships.
For the study, Weinraub and her colleagues measured patterns of nighttime sleep awakenings in infants ages six to 36 months. Her findings revealed two groups: sleepers and transitional sleepers.
"If you measure them while they are sleeping, all babies - like all adults - move through a sleep cycle every 1 1/2 to 2 hours where they wake up and then return to sleep," said Weinraub. "Some of them do cry and call out when they awaken, and that is called 'not sleeping through the night.'"
For the study, Weinraub's team asked parents of more than 1,200 infants to report on their child's awakenings at 6, 15, 24 and 36 months. They found that by six months of age, 66 percent of babies - the sleepers - did not awaken, or awoke just once per week, following a flat trajectory as they grew. But a full 33 percent woke up seven nights per week at six months, dropping to two nights by 15 months and to one night per week by 24 months.
Of the babies that awoke, the majority were boys. These transitional sleepers also tended to score higher on an assessment of difficult temperament which identified traits such as irritability and distractibility. And, these babies were more likely to be breastfed. Mothers of these babies were more likely to be depressed and have greater maternal sensitivity.
The findings suggest a couple of things, said Weinraub. One is that genetic or constitutional factors such as those that might be reflected in difficult temperaments appear implicated in early sleep problems. "Families who are seeing sleep problems persist past 18 months should seek advice," Weinraub said.