It's a conundrum that many new mothers face: comfort their babies when they wake up in the middle of the night or let them cry themselves back to sleep. Indeed, while much research in recent issues supports letting babies cry themselves to sleep, it is an uncomfortable reality for parents to accept. However, new research confirms that it is all right to let babies cry it out.

In a study published in an upcoming issue of the journal Developmental Psychology, Temple University researcher Martha Weinraub measured the sleeping patterns of infants and toddlers aged between six and 36 months. By six months, most infants - two thirds of the 1,200 children involved in the study - are able to sleep through the night. However, 33 percent of infants woke up every night even at six months. Those infants generally woke up two nights each week at 15 months and one night per week at 24 months.

The study found that the majority of babies who woke up regularly during the night after six months were boys. They were more likely to be breastfed, scored higher on personality tests assessing their irritability and distractibility, and had a greater risk of having mothers who were depressed and sensitive.

The findings suggest that sleep problems may be indicative of difficult temperaments caused by genetic and constitutional factors. Weinraub also believed that the link between sleep awakening and maternal depression merits further study. She says that women who were depressed during their child's infancy may have been depressed during pregnancy as well, affecting neural development and, later, sleep awakenings. Weinraub did also note that sleep deprivation can exacerbate depression, however.

"Because the mothers in our study described infants with many awakenings per week as creating problems for themselves and other family members, parents might be encouraged to establish more nuanced and carefully targeted routines to help babies with self-soothing and to seek occasional respite," Weinraub said in a statement. "The best advice is to put infants to bed at a regular time every night, allow them to fall asleep on their own and resist the urge to respond right away to awakenings."