In some households, anything goes — including a regular bedtime for young children. Whether suffering a neglectful childhood or enjoying a laissez-faire parental style, youngsters without a set bedtime tend to experience greater behavioral problems.

Although the effects of disrupted sleep patterns remain unclear, variances in a child’s nightly bedtime ritual at least correlates with, but does not necessarily cause, worsened behavior as measured in a long-term study by mothers and schoolteachers.

In analyzing more than 10,000 7-year-olds born in the United Kingdom at the turn of the millennium, researchers at University College London found a “meaningful” difference between children subjected to stricter versus more permissive, or haphazard, bedtime rules. Yvonne Kelly and her colleagues excluded the obvious problem child: any boy or girl diagnosed with attention deficit hyperactivity disorder, as well as any child with autism spectrum disorder.

Speculating on the underlying reasons, lead researcher Yvonne Kelly told Reuters, “If you are constantly changing the amounts of sleep you get or the different times you got to bed, it’s likely to mess up your body clock. That has all sorts of impacts on how your body is able to work the following day.”

In the study, parents tended to set more routine bedtimes for their children as they grew older, with nearly 20 percent of parents reporting no or little consistency in regular bedtimes. By the age of 5, however, that rate had fallen to nine percent, with eight percent of 7-year-olds going to bed at a regular time.

Focusing on the 7-year-old group, researchers found a moderate rise in behavioral problems among those whose parents failed to send them to bed at a regular time, before 9 p.m. On a scale of 0-40, mothers and schoolteachers rated children with regular bedtime of 6.3 to 6.9, with “wilder” children scoring 8.5 on average. However, any damage inflicted on these children failed to leave a lasting impact, Kelly said. When switching to a more regular bedtime ritual, children’s behavioral scores improved by the next reporting time.

In the usual critique of such longitudinal study, pediatric sleep specialist Jodi Mindell told Reuters she agreed about the importance of regular bedtimes for children, but questioned whether the association between bedtime and behavior might be confounded by other factors, something everyone continues to miss.

"It's very difficult to know whether or not from a study like this, is it literally the not having a regular bedtime schedule that was contributing to the difficulties or is it representative of a bigger picture?" Mindell, of St. Joseph’s University in Philadelphia, said. Still, "I think that parents need to make sleep a priority, and they need to realize that it has huge ramifications not only that evening, but the next day, the next week, the next year.”

Experts also say parents shouldn’t fret about the occasional late-night movie or sleepover with friends, so long as they maintain an overall routine.

Source: Kelly Y, Kelly J, Sacker A. Changes In Bedtime Schedules And Behavioral Difficulties In 7 Year Old Children. Pediatrics. 2013.